Keisuke Hosokawa
| Department of Computer and Network Engineering | Professor |
| Cluster II (Emerging Multi-interdisciplinary Engineering) | Professor |
| Center for Space Science and Radio Engineering | Professor |
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- Apr. 2024
電気通信大学 宇宙・電磁環境研究センター センター長 - 01 Apr. 2019
電気通信大学大学院, 情報理工学研究科 情報・ネットワーク工学専攻, 教授 - 01 Apr. 2016 - 31 Mar. 2019
電気通信大学大学院, 情報理工学研究科 情報・ネットワーク工学専攻, 准教授 - 01 Jun. 2012 - 31 Mar. 2016
電気通信大学, 大学院 情報理工学研究科 情報・通信工学専攻, 准教授 - 01 Apr. 2007 - 31 May 2012
Department of Information and Communication Engineering, The University of Electro-Communications, 情報通信工学科, Assistant Professor - 01 Apr. 2007 - 31 May 2012
Department of Information and Communication Engineering, The University of Electro-Communications, Assistant Professor - 01 Apr. 2003 - 31 Mar. 2007
Department of Information and Communication Engineering, The University of Electro-Communications, 情報通信工学科, Research Associate - 01 Apr. 2003 - 31 Mar. 2007
Department of Information and Communication Engineering, The University of Electro-Communications, Research Associate - Apr. 2002 - Mar. 2003
京都大学大学院 理学研究科, 日本学術振興会特別研究員
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Paper
- Post-midnight purple arc and patches appeared on the high latitude part of the auroral oval: Dawnside counterpart of STEVE?
Sota Nanjo; Gabriel Arne Hofstra; Kazuo Shiokawa; Atsuki Shinbori; Satonori Nozawa; Keisuke Hosokawa
Earth, Planets and Space, 76, 1, Dec. 2024, The phenomenon known as strong thermal emission velocity enhancement (STEVE) is a purple/mauve arc-shaped atmospheric glow observed at lower latitudes of the auroral oval on the duskside. Simultaneous observations using a ground-based camera and a low-altitude satellite have shown that STEVE is accompanied by rapid westward ion flows. Such fast ion flows are termed the subauroral ion drift (SAID) or subauroral polarization stream (SAPS). Similarly, an eastward fast ion flow known as the dawnside auroral polarization stream (DAPS) is observed within the Region 1 current on the dawnside. If the optical phenomenon triggered by SAID/SAPS corresponds to STEVE, a comparable optical phenomenon should be driven by DAPS. Thus far, however, such a phenomenon has not been reported. This study discovers, for the first time, a purple-colored optical phenomenon characterized by the fast eastward ion flows, a possible signature of DAPS, occurring poleward of the bright green arc in the post-midnight sector. We present color all-sky images obtained by a ground-based commercial digital camera, along with wide-coverage optical measurements and in-situ data from low-altitude satellites. The results imply that this glow requires not only a high-speed ion flow but also its sharp latitudinal gradient at the boundary between the Region 1 and 2. Graphical Abstract: (Figure presented.)
Scientific journal - New observational projects in New Zealand for studying radiation belt loss processes in the deep inner magnetosphere: instrumentation, operation by solar power and initial results
Yuki Obana; Kaori Sakaguchi; Masahito Nosé; Keisuke Hosokawa; Peter Jaquiery; Satoko Saita; Kazuo Shiokawa; Martin Connors; Akira Kadokura; Tsutomu Nagatsuma; Tanja Petersen
Earth, Planets and Space, Springer Science and Business Media LLC, 76, 1, 15 Mar. 2024, Abstract
This paper describes the instrumentation and the first results of an upper atmospheric observing project conducted in New Zealand. We operate an all-sky aurora camera and a 64-Hz sampling induction magnetometer at Middlemarch, as well as 1-Hz sampling fluxgate magnetometers which have been operative at three stations in New Zealand, Middlemarch, Eyrewell and Te Wharau. Green and red auroras corresponding to the 557.7 nm and 630.0 nm emissions, respectively, were observed on the night of 5 August 2019. Pc1 pulsations were observed in the frequency range of ~ 0.2–1 Hz before and after a small (minimum Dst = − 40 nT) geomagnetic storm during 4–6 October 2020. Before the geomagnetic storm, Pc1 pulsations with several center frequencies were observed regardless of local time. During the recovery phase, an IPDP (interval of pulsations of diminishing period) type of Pc1 and four subsequent intervals of Pc1s were detected. The Ionospheric Alfvén Resonator (IAR) was also identified with spectral resonance structures during this magnetic storm. Lower harmonic modes of the IAR were present throughout the local nighttime, but higher harmonic modes with frequency of 5–15 Hz seemed to disappear at the onset time of substorms. This is the first report of the IAR at such a high frequency range and this is the first IAR observation in the southern hemisphere. Examples of applying cross-phase analysis to observation data of fluxgate magnetometers are also given.
Graphical Abstract
Scientific journal - Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry-Perot Interferometer in Tromsø, Norway Since 2009
S. Oyama; H. Vanhamäki; L. Cai; A. Shinbori; K. Hosokawa; T. Sakanoi; K. Shiokawa; A. Aikio; I. I. Virtanen; Y. Ogawa; Y. Miyoshi; S. Kurita; N. Nishitani
Space Weather, 22, 3, Mar. 2024, Solar cycles 24–25 were quiet until a geomagnetic storm with a Sym-H index of −170 nT occurred in late March 2023. On March 23–24, a Fabry-Perot interferometer (FPI; 630 nm) in Tromsø, Norway, recorded the highest thermospheric wind speed of over 500 m/s since 2009. Comparisons with magnetometer readings in Scandinavia showed that a large amount of electromagnetic energy was transferred to the ionosphere-thermosphere system. Total electron content maps suggested an enlarged auroral oval and revealed that the FPI observed winds near the polar cap instead of inside the oval for a long period during the storm main phase. The FPI wind had a strong equatorward component during the storm, likely because of the powerful anti-sunward ionospheric plasma flow in the polar cap. The positive Y-component of the IMF for 6 days before the storm caused a successive westward component of the FPI-measured wind during the storm main phase. On March 24, the first day of the storm recovery phase, thermospheric wind disturbed and the ionospheric density decreased significantly at high latitudes. This density depression lasted for several days, and a large amount of electromagnetic energy during the storm modified the thermospheric dynamics and ionospheric plasma density.
Scientific journal - Multi-Instrument Observations of the Evolution of Polar Cap Patches Associated With Flow Shears and Particle Precipitation
Duan Zhang; Qing He Zhang; Kjellmar Oksavik; Zan Yang Xing; L. R. Lyons; Hui Gen Yang; Guo Jun Li; Keisuke Hosokawa; Atsuki Shinbori; Yu Zhang Ma; Yong Wang; Xiang Yu Wang
Journal of Geophysical Research: Space Physics, 128, 12, Dec. 2023, Simultaneous observations from Defense Meteorological Satellite Program, Swarm, Resolute Bay all-sky imagers, GPS Total Electron Content and Super Dual Auroral Radar Network, are used to investigate the evolution and key characteristics of the Tongue of Ionization (TOI) being restructured into a polar cap patch. Six satellites crossed the TOI of patch as it moved from the dayside to the nightside. It was initially hot, then a mix of both cold and hot, and finally it became a cold patch. This suggests that cold patch is not only a result of solar extreme ultraviolet radiation, but may also develop when a hot patch cools down. Soft-electron precipitation and flow shears both contribute to the TOI restructuring and the appearance of polar cap patch. The plasma density of patch at ∼500 km was at least 4 times higher than at ∼800 km. The plasma density enhancement gradually decreased as the patch evolved due to decreased production and transport of cold nightside low-density plasma. Moreover, the duskward motion of the patch was influenced by changes in the ionospheric convection pattern.
Scientific journal - Anomalous Long-Distance Propagation of ILS LOC Signals by the Es Layer and Its Impact on Aviation Receivers
Susumu Saito; Keisuke Hosokawa; Jun Sakai; Ichiro Tomizawa
Space Weather, 21, 11, 15 Nov. 2023, Peer-reviwed, Anomalous long-distance propagation of Very High Frequency radio waves of aeronautical navigation systems was investigated by an airborne Instrument Landing System (ILS) localizer (ILS LOC) receiver installed on the ground at Kure, Japan (34.245°N, 132.528°E). Intense ILS LOC type signals were observed and the received power was strong enough for the aviation receiver to output course deviation. The radio source was identified by receiving the Morse Code for identification as the localizer-type directional aid (LDA) serving the Runway-21 of the Hualien Airport, Taiwan (24.0396°N, 121.6221°E) of which beam pointed close to the receiver. This result supports that the source of the signals often observed at the same frequency at the same location is most probably the LDA at the Hualien Airport. The maximum received power was −99 dBm for an omni-directional antenna. It was strong enough to cause co-channel interference. Considering stronger power (−70 dBm) found in previous observations at the same frequency at the same location, anomalous propagation of ILS LOC signals by the Es layer could be a cause of interference when a receiver was near the center of the ILS LOC beam. The course deviation output was consistent with the geometry between the beam of Runway-21 LDA at the Hualien Airport and the receiver. However, the observed course deviation fluctuated remarkably even when the received power was strong enough. The fluctuation of the course deviation may indicate the structure of the Es layer, and observation of the course deviation could be used to diagnose the Es layer structure.
Scientific journal - Simultaneous observations of equatorial plasma bubbles with an all-sky airglow imager and a HF Doppler sounding system in Taiwan
Hiromi Sejima; Keisuke Hosokawa; Hiroyuki Nakata; Jaroslav Chum; Chien-Hung Lin; Jia-Ting Lin
Earth, Planets and Space, Springer Science and Business Media LLC, 75, 1, 10 Oct. 2023, Abstract
High-Frequency Doppler (HFD) sounders at low-latitudes often detect characteristic oblique spreading Doppler traces in the spectrogram, known as Oblique Spread Structure (OSS). OSS has been expected to be generated by the dispersion of radio wave reflection due to equatorial plasma bubbles (EPBs). However, it has not yet been confirmed whether OSS is surely a manifestation of EPB by conducting simultaneous observations of EPB and OSS with different observational techniques. Additionally, it remains unclear what kinds of properties of EPB are reflected in the fine structure of OSS. In this study, we investigated three cases of OSSs and EPBs simultaneously observed by a HFD sounding system and an all-sky airglow imager in Taiwan. For the three cases presented here, the timing of OSS occurrence in the HFD data well coincided with that of the EPB appearance in the airglow data. The frequency shift of OSS is quantitatively explained assuming a radio wave reflection at 250–300 km altitudes. These results strongly indicate that OSS is formed by electron density variations at F-region altitudes accompanying EPB; thus, OSS is a manifestation of EPB in the HFD observations. Furthermore, it was suggested that the fine structure of OSS reflected the branching structure of EPB when the multiple branches of EPB reached the intermediate reflection point of the HFD observation. The detection of EPB occurrence and its fine structure using HFD observation enables monitoring of EPB regardless of weather conditions, which will contribute to monitoring the space weather impact of EPBs, for example, on GNSS navigation, in a wide area.
Graphical Abstract
Scientific journal - Periodic oscillations of Doppler frequency excited by the traveling ionospheric disturbances associated with the Tonga eruption in 2022
Hiroyuki Nakata; Keisuke Hosokawa; Susumu Saito; Yuichi Otsuka; Ichoro Tomizawa
Earth, Planets and Space, Springer Science and Business Media LLC, 75, 1, 10 Oct. 2023, Abstract
The explosive eruption of the Hunga Tonga-Hunga Ha’apai volcano on 15 January 2022 generated atmospheric waves traveling around the Earth, which caused ionospheric disturbances on various spatio-temporal scales. A HF Doppler sounding system in Japan detected characteristic ionospheric disturbances showing periodic oscillations in the Doppler frequency with a period of ~ 4 min. In this study, such periodic oscillations were examined by comparing Doppler frequency data with Total Electron Content data obtained by Global Navigation Satellite System. The observed periodic oscillations in the Doppler frequency were characterized by a sawtooth or S-letter shaped variation, implying the passage of the traveling ionospheric disturbances through the reflection points of the HF Doppler sounding system. It was also found that the periodic oscillations occurred prior to the arrival of the tropospheric Lamb wave excited by the Tonga eruption. From the total electron content data, the traveling ionospheric disturbances causing the periodic oscillations were excited by the tropospheric Lamb waves at the conjugate point in the southern hemisphere, namely, the electric field perturbations due to the Lamb waves in the southern hemisphere mapped onto the sensing area of the HF Doppler sounding system in the northern hemisphere along the magnetic field lines. The periodic oscillations were observed only in the path between Chofu transmitter and Sarobetsu receiver, whose the radio propagation path is almost aligned in the north–south direction. This suggests that the traveling ionospheric disturbance has a structure elongating in the meridional direction. The variation in the Doppler frequency was reproduced by using a simple model of the propagation of the traveling ionospheric disturbances and the resultant motion of the reflection point. As a result, the vertical motion of the reflection point associated with the periodic oscillations was estimated to be about 1 km. It is known that 4-min period variations are sometimes observed in association with earthquakes, which is due to resonances of acoustic mode waves propagating between the ground and the lower ionosphere. Therefore, a similar resonance structure in the southern hemisphere is a plausible source of the traveling ionospheric disturbances detected in the northern hemisphere.
Graphical Abstract
Scientific journal - Monitoring of equatorial plasma bubbles using aeronautical navigation system: a feasibility study
Keisuke Hosokawa; Susumu Saito; Hiroyuki Nakata; Chien-Hung Lin; Jia-Ting Lin; Pornchai Supnithi; Ichiro Tomizawa; Jun Sakai; Toru Takahashi; Takuya Tsugawa; Michi Nishioka; Mamoru Ishii
Earth, Planets and Space, Springer Science and Business Media LLC, 75, 1, 03 Oct. 2023, Abstract
It has long been known that field-aligned irregularities within equatorial plasma bubbles (EPBs) can cause long-range propagation of radio waves in the VHF frequencies such as those used for TV broadcasting through the so-called forward scattering process. However, no attempt has been made to use such anomalous propagations of VHF radio waves for wide-area monitoring of EPBs. In this study, we investigated the feasibility of monitoring of EPBs using VHF radio waves used for aeronautical navigation systems such as VHF Omnidirectional radio Range (VOR). There are 370 VOR stations in the Eastern and Southeastern Asian region that can be potentially used as Tx stations for the observations of anomalous propagation. We have examined the forward scattering conditions of VHF waves using the magnetic field model and confirmed that it is possible to observe the EPB-related anomalous propagation if we set up Rx stations in Okinawa (Japan), Taiwan, and Thailand. During test observations conducted in Okinawa since 2021, no signal has been received that was clearly caused by anomalous propagation due to EPBs. This is simply because EPBs have not developed to high latitudes during the observation period due to the low solar activity. In March 2023, however, possible indications of EPB-related scattering were detected in Okinawa which implies the feasibility of observing EPBs with the current observation system. We plan to conduct pilot observations in Taiwan and Thailand in future to further evaluate the feasibility of this monitoring technique.
Graphical Abstract
Scientific journal - Correspondence of Pi2 pulsations, aurora luminosity, and plasma flux fluctuation near a substorm brightening aurora: Arase observations
L. Chen; K. Shiokawa; Y. Miyoshi; S. Oyama; C‐W. Jun; Y. Ogawa; K. Hosokawa; Y. Kazama; S. Y. Wang; S. W. Y. Tam; T. F. Chang; B. J. Wang; K. Asamura; S. Kasahara; S. Yokota; T. Hori; K. Keika; Y. Kasaba; A. Kumamoto; F. Tsuchiya; M. Shoji; Y. Kasahara; A. Matsuoka; I. Shinohara; S. Nakamura
Journal of Geophysical Research: Space Physics, American Geophysical Union (AGU), 128, 10, 28 Sep. 2023, Abstract
Although many substorm‐related observations have been made, we still have limited insight into propagation of the plasma and field perturbations in Pi2 frequencies (∼7‐25 mHz) in association with substorm aurora, particularly from the auroral source region in the inner magnetosphere to the ground. In this study, we present conjugate observations of a substorm brightening aurora using an all‐sky camera and an inner‐magnetospheric satellite Arase at L ∼ 5. A camera at Gakona (62.39oN, 214.78oE), Alaska, observed a substorm auroral brightening on December 28, 2018, and the footprint of the satellite was located just equatorward of the aurora. Around the timing of the auroral brightening, the satellite observed a series of quasi‐periodic variations in the electric and magnetic fields and in the energy flux of electrons and ions. We demonstrate that the diamagnetic variations of thermal pressure and medium‐energy ion energy flux in the inner magnetosphere show approximately one‐to‐one correspondence with the oscillations in luminosity of the substorm brightening aurora and high‐latitudinal Pi2 pulsations on the ground. We also found their anti‐correlation with low‐energy electrons. Cavity‐type Pi2 pulsations were observed at mid‐ and low‐latitudinal stations. Based on these observations, we suggest that a wave phenomenon in the substorm auroral source region, like ballooning type instability, play an important role in the development of substorm and related auroral brightening and high‐latitude Pi2, and that the variation of the auroral luminosity was directly driven by keV electrons which were modulated by Alfven waves in the inner magnetosphere.
Scientific journal - Three-dimensional ionospheric conductivity associated with pulsating auroral patches: Reconstruction from ground-based optical observations
Mizuki Fukizawa; Yoshimasa Tanaka; Yasunobu Ogawa; Keisuke Hosokawa; Tero Raita
Copernicus GmbH, 04 Aug. 2023, Abstract. Pulsating auroras (PsAs) appear over a wide area within the aurora oval from the midnight sector to the noon sector. In previous studies, observations by magnetometers onboard satellites have reported the presence of field-aligned currents (FACs) near the edges and interiors of pulsating aurora patches. PsAs are thus a key research target for understanding the magnetosphere–ionosphere coupling process. However, the three-dimensional (3-D) structure of the electric currents has yet to be clarified, since each satellite observation is limited to the single dimension along its orbit. This study’s aim was a reconstruction of the 3-D structure of ionospheric conductivity, which is necessary to elucidate the 3-D ionospheric current. Tomographic analysis was used to estimate the 3-D ionospheric conductivity for rapidly changing auroral phenomena such as PsAs. The reconstructed Hall conductivity reached its maximum value of 1.4 × 10–3 S m–1 at 94 km altitude, while the Pedersen conductivity reached its maximum value of 2.6 × 10–4 S m–1 at 116 km altitude. The Pedersen conductivity, which is driven by the motion of electrons, exhibited a secondary peak value of 9.9 × 10–5 S m–1 at 86 km altitude. The electron Pedersen conductivity maximum value in the D region was approximately 38 % of the ion Pedersen conductivity maximum value in the E region. The FAC, derived under the assumption of a uniform ionospheric electric field, was approximately 70 µA m–2 near the edge of the PsA patch. This FAC value was approximately 10 times that observed by satellites in previous studies. If the conductivity around the patch is underestimated or the assumption of a uniform field distribution is incorrect, the FAC could be overestimated. On the contrary, due to sharper boundary structures, the FAC could actually have had such a large FAC. - An Implication of Detecting the Internal Modulation in a Pulsating Aurora: A Conjugate Observation by the Arase Satellite and All‐Sky Imagers
S. Nanjo; S. Ebukuro; S. Nakamura; Y. Miyoshi; S. Kurita; S.‐I. Oyama; Y. Ogawa; K. Keika; Y. Kasahara; S. Kasahara; A. Matsuoka; T. Hori; S. Yokota; S. Matsuda; I. Shinohara; S.‐Y. Wang; Y. Kazama; C.‐W. Jun; M. Kitahara; K. Hosokawa
Journal of Geophysical Research: Space Physics, American Geophysical Union (AGU), 128, 8, 03 Aug. 2023, Abstract
A physical mechanism to produce pulsating aurora (PsA) has been considered to be the interaction of the electron and the chorus wave generated near the equatorial plane of the magnetosphere. A recent observation of high temporal resolution of chorus waves by the Arase satellite revealed that the presence or absence of the internal modulation of PsA, which is a characteristic sub‐second scintillation at 3 ± 1 Hz within each optical pulsation, is closely related to the discreteness of the element structure of the chorus wave. However, it is still unclear what parameters (or conditions) control the discreteness of the element and the existence of the internal modulation of PsA. In this study, we discuss parameters that determine the presence or absence of the internal modulation of PsA and element structure of chorus by showing a conjugate observation of PsA/chorus by ground‐based cameras and the Arase satellite. During the event, the occurrence of internal modulation increased temporally. The wave data from the satellite show that the repetitive frequency of elements was ∼6 Hz when the internal modulation was indistinct, while the repetitive frequency was ∼3 Hz when the internal modulation was distinct. The particle measurements suggest that this difference was caused by changes in the density and the temperature anisotropy of the hot electron. The internal modulation was clearly observed when the density of hot electrons decreased and the temperature anisotropy relaxed after the injection. Observations of internal modulations from the ground might allow us to estimate the parameters such as energetic electron density and temperature anisotropy in the magnetosphere.
Scientific journal - A Ground‐Based Instrument Suite for Integrated High‐Time Resolution Measurements of Pulsating Aurora With Arase
K. Hosokawa; S.‐I. Oyama; Y. Ogawa; Y. Miyoshi; S. Kurita; M. Teramoto; S. Nozawa; T. Kawabata; Y. Kawamura; Y.‐M. Tanaka; H. Miyaoka; R. Kataoka; K. Shiokawa; U. Brändström; E. Turunen; T. Raita; M. G. Johnsen; C. Hall; D. Hampton; Y. Ebihara; Y. Kasahara; S. Matsuda; I. Shinohara; R. Fujii
Journal of Geophysical Research: Space Physics, American Geophysical Union (AGU), 128, 8, 28 Jul. 2023, Abstract
A specialized ground‐based system has been developed for simultaneous observations of pulsating aurora (PsA) and related magnetospheric phenomena with the Arase satellite. The instrument suite is composed of (a) six 100 Hz sampling high‐speed all‐sky imagers (ASIs), (b) two 10 Hz sampling monochromatic ASIs observing 427.8 and 844.6 nm auroral emissions, (c) a 20 Hz sampling fluxgate magnetometer. The 100 Hz ASIs were deployed in four stations in Scandinavia and two stations in Alaska, which have been used for capturing the main pulsations and quasi 3 Hz internal modulations of PsA at the same time. The 10 Hz sampling monochromatic ASIs have been operative in Tromsø, Norway with the 20 Hz sampling magnetometer. Combination of these multiple instruments with the European Incoherent SCATter (EISCAT) radar enables us to detect the low‐altitude ionization due to energetic electron precipitation during PsA and further to reveal the ionospheric electrodynamics behind PsA. Since the launch of the Arase satellite, the data from these instruments have been examined in comparison with the wave and particle data from the satellite in the magnetosphere. In the future, the system can be utilized not only for studies of PsA but also for other classes of aurora in close collaboration with the planned EISCAT_3D project.
Scientific journal - IMF Dependence of Midnight Bifurcation in the Thermospheric Wind at an Auroral Latitude Based on Nine Winter Measurements in Tromsø, Norway
S. Oyama; K. Hosokawa; H. Vanhamäki; A. Aikio; T. Sakanoi; L. Cai; I. I. Virtanen; K. Shiokawa; N. Nishitani; A. Shinbori; Y. Ogawa
Geophysical Research Letters, American Geophysical Union (AGU), 50, 14, 24 Jul. 2023
Scientific journal - Geomagnetic activity dependence and dawn-dusk asymmetry of thermospheric winds from 9-year measurements with a Fabry–Perot interferometer in Tromsø, Norway
Shin-ichiro Oyama; Anita Aikio; Takeshi Sakanoi; Keisuke Hosokawa; Heikki Vanhamäki; Lei Cai; Ilkka Virtanen; Marcus Pedersen; Kazuo Shiokawa; Atsuki Shinbori; Nozomu Nishitani; Yasunobu Ogawa
Earth, Planets and Space, Springer Science and Business Media LLC, 75, 1, 05 May 2023, Abstract
Ion drag associated with the ionospheric plasma convection plays an important role in the high-latitude thermospheric dynamics, yet changes in the thermospheric wind with geomagnetic activity are not fully understood. We performed a statistical analysis of the thermospheric wind measurements with a Fabry–Perot interferometer (FPI; 630 nm wavelength) in Tromsø, Norway, in the winter months for 9 years. The measurements were sorted by a SuperMAG (SME) index, and a quiet-time wind pattern was defined as an hourly mean under SME ≤ 40 nT. The quiet-time wind pattern can be expected to be represented by a pressure gradient associated with the solar radiation and a geostrophic force balance. With an increase in the geomagnetic activity level, the thermospheric wind turned over from eastward to westward at dusk and increased the equatorward magnitude from midnight to dawn. Deviations from the quiet-time wind presented similar patterns in the direction with the ionospheric plasma convection but were larger in magnitude at dusk than at dawn. This is the first study to report a dawn-dusk asymmetry of the thermospheric wind acceleration feature and signatures of the eastward wind acceleration at dawn by ion drag.
Graphical Abstract
Scientific journal - Simultaneous Precipitation of Sub-Relativistic Electron Microburst and Pulsating Aurora Electrons
Taku Namekawa; Takefumi Mitani; Kazushi Asamura; Yoshizumi Mioshi; Keisuke Hosokawa; Marc R Lessard; Chrystal Moser; Alexa J. Halford; Takeshi Sakanoi; Miki Kawamura; Masahito Nosé; Reiko Nomura; Mariko Teramoto; Mykhaylo Shumko; Kristina A Lynch; Allison N Jaynes; Matthew G McHarg
Geophysical Research Letters, 16 Apr. 2023, Peer-reviwed
Scientific journal - Atmospheric and ionospheric waves induced by the Hunga eruption on 15 January 2022; Doppler sounding and infrasound
Jaroslav Chum; Tereza Šindelářová; Petra Koucká Knížová; Kateřina Podolská; Jan Rusz; Jiří Baše; Hiroyuki Nakata; Keisuke Hosokawa; Michael Danielides; Carsten Schmidt; Leon Knez; Jann-Yenq Liu; María Graciela Molina; Mariano Fagre; Zama Katamzi-Joseph; Hiroyo Ohya; Tatsuya Omori; Jan Laštovička; Dalia Obrazová Burešová; Daniel Kouba; Jaroslav Urbář; Vladimír Truhlík
Geophysical Journal International, Oxford University Press (OUP), 233, 2, 1429-1443, 24 Dec. 2022, Peer-reviwed, Summary
The massive explosive eruption of the Hunga volcano on 15 January 2022 generated atmospheric waves that were recorded around the globe and affected the ionosphere. The paper focuses on observations of atmospheric waves in the troposphere and ionosphere in Europe, however, a comparison with observations in East Asia, South Africa and South America is also provided. Unlike most recent studies of waves in the ionosphere based on the detection of changes in the total electron content, this study builds on detection of ionospheric motions at specific altitudes using continuous Doppler sounding. In addition, much attention is paid to long-period infrasound (periods longer than ∼50 s), which in Europe is observed simultaneously in the troposphere and ionosphere about an hour after the arrival of the first horizontally propagating pressure pulse (Lamb wave). It is shown that the long-period infrasound propagated approximately along the shorter great circle path, similar to the previously detected pressure pulse in the troposphere. It is suggested that the infrasound propagated in the ionosphere probably due to imperfect refraction in the lower thermosphere. The observation of infrasound in the ionosphere at such large distances from the source (over 16 000 km) is rare and differs from ionospheric infrasound detected at large distances from the epicenters of strong earthquakes, because in the latter case the infrasound is generated locally by seismic waves. An unusually large traveling ionospheric disturbance (TID) observed in Europe and associated with the pressure pulse from the Hunga eruption is also discussed. Doppler sounders in East Asia, South Africa and South America did not record such a significant TID. However, TIDs were observed in East Asia around times when Lamb waves passed the magnetically conjugate points. A probable observation of wave in the mesopause region in Europe approximately 25 min after the arrival of pressure pulse in the troposphere using a 23.4 kHz signal from a transmitter 557 km away and a coincident pulse in electric field data are also discussed.
Scientific journal, English - Observation of Source Plasma and Field Variations of a Substorm Brightening Aurora at L ∼ 6 by a Ground-Based Camera and the Arase Satellite on 12 October 2017
L. Chen; K. Shiokawa; Y. Miyoshi; S. Oyama; C. W. Jun; Y. Ogawa; K. Hosokawa; Y. Inaba; Y. Kazama; S. Y. Wang; S. W.Y. Tam; T. F. Chang; B. J. Wang; K. Asamura; S. Kasahara; S. Yokota; T. Hori; K. Keika; Y. Kasaba; A. Kumamoto; F. Tsuchiya; M. Shoji; Y. Kasahara; A. Matsuoka; I. Shinohara; S. Imajo; S. Nakamura; M. Kitahara
Journal of Geophysical Research: Space Physics, 127, 11, Nov. 2022, Auroral brightening is one of the most common phenomena that occur during substorm onset and is usually recognized as a projection of the substorm-associated magnetospheric plasma dynamics to the ionosphere. However, electromagnetic fields and plasma features associated with the substorm brightening arc have not been well understood. In this study, we present a comprehensive observation of the source plasma and field variations of a substorm brightening aurora in the inner magnetosphere. We performed a unique conjugate observation of a substorm brightening auroral arc observed by a ground-based camera and by the Arase satellite in the magnetospheric source region at L ∼ 6. The event was observed at Tromsø (69.6°N, 19.2°E), Norway, on 12 October 2017. The brightening arc indicates east-west structures with longitudinal scales of ∼0.5°–2.0°. Field-aligned bi-directional electrons with an energy range between 66 and 1,800 eV were detected by the satellite, simultaneously with the appearance of the brightening arc in the camera. These electrons were probably supplied from the auroral brightening region in the ionosphere, indicating that the satellite was on the same field line of the brightening aurora. The magnetic and electric field data show characteristic fluctuations and earthward Poynting flux around the time that the satellite crossed the aurora. Anti-phase oscillations between the thermal pressure and the magnetic pressure are also reported. Based on these observations, we suggest the possibility that a ballooning instability occurred in the source region of the substorm brightening arc in the inner magnetosphere at L ∼ 6.
Scientific journal - Proton aurora and relativistic electron microbursts scattered by electromagnetic ion cyclotron waves
Shumko, M; Gallardo-Lacourt, B; Halford, A. J; Blum, L. W; Liang, J; Miyoshi, Y; Hosokawa, K; Donovan, E; Mann, I. R; Murphy, K; Spanswick, E. L; Blake, J. B; Looper, M. D; Gillies, D. M
Front. Astron. Space Sci., 9:975123, doi:10.3389/fspas.2022.975123, Aug. 2022, Peer-reviwed
Scientific journal, English - Reconstruction of precipitating electrons and three-dimensional structure of a pulsating auroral patch from monochromatic auroral images obtained from multiple observation points
Mizuki Fukizawa; Takeshi Sakanoi; Yoshimasa Tanaka; Yasunobu Ogawa; Keisuke Hosokawa; Björn Gustavsson; Kirsti Kauristie; Alexander Kozlovsky; Tero Raita; Urban Brändström; Tima Sergienko
Annales Geophysicae, Copernicus GmbH, 40, 4, 475-484, 12 Jul. 2022, Abstract. In recent years, aurora observation networks usinghigh-sensitivity cameras have been developed in the polar regions. Thesenetworks allow dimmer auroras, such as pulsating auroras (PsAs), to beobserved with a high signal-to-noise ratio. We reconstructed the horizontaldistribution of precipitating electrons using computed tomography withmonochromatic PsA images obtained from three observation points. Thethree-dimensional distribution of the volume emission rate (VER) of the PsAwas also reconstructed. The characteristic energy of the reconstructedprecipitating electron flux ranged from 6 to 23 keV, and the peak altitudeof the reconstructed VER ranged from 90 to 104 km. We evaluated the resultsusing a model aurora and compared the model's electron density with theobserved one. The electron density was reconstructed correctly to someextent, even after a decrease in PsA intensity. These results suggest thatthe horizontal distribution of precipitating electrons associated with PsAscan be effectively reconstructed from ground-based optical observations.
Scientific journal - Instantaneous Achievement of the Hall and Pedersen–Cowling Current Circuits in Northern and Southern Hemispheres During the Geomagnetic Sudden Commencement on 12 May 2021
Kikuchi, T; Araki, T; Hashimoto, K. K; Ebihara, Y; Tanaka, T; Nishimura, Y; Vichare, G; Sinha, A. K; Chum, J; Hosokawa, K; Tomizawa, I; Tanaka, Y; Kadokura, A
Front. Astron. Space Sci., 9:879314, doi:10.3389/fspas.2022.879314, May 2022, Peer-reviwed
Scientific journal, English - An automated auroral detection system using deep learning: real-time operation in Tromsø, Norway
Nanjo, S; Nozawa, S; Yamamoto; M. Kawabata, T; Johnsen, M. G; Tsuda, T. T; Hosokawa, K
Scientific Reports, 12, doi:10.1038/s41598-022-11686-8, May 2022, Peer-reviwed
Scientific journal, English - Slow Contraction of Flash Aurora Induced by an Isolated Chorus Element Ranging From Lower-Band to Upper-Band Frequencies in the Source Region
Mitsunori Ozaki; Satoshi Yagitani; Kazuo Shiokawa; Yoshimasa Tanaka; Yasunobu Ogawa; Keisuke Hosokawa; Yoshiya Kasahara; Yusuke Ebihara; Yoshizumi Miyoshi; Kousuke Imamura; Ryuho Kataoka; Shin-ichiro Oyama; Teppei Chida; Akira Kadokura
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 49, 9, May 2022, Flash aurora driven by an isolated chorus element can be a useful ionospheric indicator for identifying the source wave properties via wave-particle interactions. Using ground observation and modeling approaches, here we report the temporal characteristics of flash aurora that depend on the chorus frequency width and the sweep rate. We found that the contraction time increases more than the expansion time in patchy auroral variations, due to the difference in the minimum electron energies resonated with the chorus wave packet away from the equatorial source to higher latitudes. Especially, the contraction time strongly depends on the higher-frequency chorus waves due to cyclotron resonance with lower-energy electrons. The model calculations support that the chorus element ranges from lower-band to upper-band frequencies with respect to half the gyrofrequency at the exact generation region. Our study provides the prompt (milliseconds) chorus-driven electron dynamics through the spatiotemporal characteristics of flash aurora in the ionosphere.
Scientific journal, English - On the importance of using event-specific chorus wave dynamics in simulating diffuse electron precipitation
Yu, Y; K. Hosokawa; B. Ni; V. Jordanova; Y. Miyoshi; X. Tian; L. Ma; J. Cao
Journal of Geophysical Research: Space Physics, 127, doi:10.1029/2021JA029918, Apr. 2022, Peer-reviwed
Scientific journal, English - Propagation characteristics of sporadic E and medium-scale traveling ionospheric disturbances (MSTIDs): statistics using HF Doppler and GPS-TEC data in Japan
Ryo Matsushima; Keisuke Hosokawa; Jun Sakai; Yuichi Otsuka; Mitsumu K. Ejiri; Michi Nishioka; Takuya Tsugawa
EARTH PLANETS AND SPACE, SPRINGER, 74, 1, Apr. 2022, We carried out a statistical analysis of the propagation characteristics of Es and Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) by combining data of HF Doppler (HFD) sounder and Total Electron Content (TEC) obtained from the GPS receivers of GEONET (GPS-TEC) for 4 years from 2014 to 2017. We made use of Es reflection data from the HFD receivers in Sugito, Saitama (36.0 degrees N, 139.7 degrees E), Fujisawa, Kanagawa (35.3 degrees N, 139.5 degrees E), and Sugadaira, Nagano (36.4 degrees N, 138.3 degrees E) in Japan. By using this triangle observation, we succeeded in deriving the horizontal speed and direction of the motion of Es. In addition, we estimated the phase velocity of MSTIDs observed in the simultaneously obtained maps of GPS-TEC with the same triangle observation procedure. The speeds of Es and MSTIDs were commonly less than 100 m/s in most cases and their propagation direction was predominantly southwestward. This result is consistent with the statistical characteristics of nighttime MSTIDs observed in the previous studies. More importantly, good correspondence between the propagation characteristics of the two phenomena at two different altitudes confirms that Es and MSTIDs move in tandem with each other, further suggesting that Es in the E region plays an important role in the generation and propagation of MSTIDs in the F region.
Scientific journal, English - Energetic electron precipitations by chorus waves and its impact on the middleatmosphere
Yoshizumi Miyoshi; Shinji Saito; Keisuke Hosokawa; Kazushi Asamura; Shinichiro Oyama; Takefumi Mitani; Takeshi Sakanoi; Antti Kero; Esa Turunen; Pekka Verronen
Copernicus {GmbH}, 28 Mar. 2022
Scientific journal - GEO-X (GEOspace X-ray imager)
Yuichiro Ezoe; Ryu Funase; Harunori Nagata; Yoshizumi Miyoshi; Hiroshi Nakajima; Ikuyuki Mitsuishi; Kumi Ishikawa; Yosuke Kawabata; Shintaro Nakajima; Landon Kamps; Masaki Numazawa; Tomokage Yoneyama; Kouichi Hagino; Yosuke Matsumoto; Keisuke Hosokawa; Satoshi Kasahara; Junko Hiraga; Kazuhisa Mitsuda; Masaki Fujimoto; Munetaka Ueno; Atsushi Yamazaki; Hiroshi Hasegawa; Takefumi Mitani; Yasuhiro Kawakatsu; Takahiro Iwata; Hiroyuki Koizumi; Hironori Sahara; Yoshiaki Kanamori; Kohei Morishita
SPACE TELESCOPES AND INSTRUMENTATION 2022: ULTRAVIOLET TO GAMMA RAY, SPIE-INT SOC OPTICAL ENGINEERING, 12181, 2022, GEO-X (GEOspace X-ray imager) is a small satellite mission aiming at visualization of the Earth's magnetosphere by X-rays and revealing dynamical couplings between solar wind and magnetosphere. In-situ spacecraft have revealed various phenomena in the magnetosphere. In recent years, X-ray astronomy satellite observations discovered soft X-ray emission originated from the magnetosphere. We therefore develop GEO-X by integrating innovative technologies of the wide FOV X-ray instrument and the microsatellite technology for deep space exploration. GEO-X is a 50 kg class microsatellite carrying a novel compact X-ray imaging spectrometer payload. The microsatellite having a large delta v (>700 m/s) to increase an altitude at 40-60 R-E from relatively low-altitude (e.g., Geo Transfer Orbit) piggyback launch is necessary. We thus combine a 18U Cubesat with the hybrid kick motor composed of liquid N2O and polyethylene. We also develop a wide FOV (5x5 deg) and a good spatial resolution (10 arcmin) X-ray (0.3-2 keV) imager. We utilize a micromachined X-ray telescope, and a CMOS detector system with an optical blocking filter. We aim to launch the satellite around the 25th solar maximum.
International conference proceedings, English - Statistical Study of Electron Density Enhancements in the Ionospheric F Region Associated With Pulsating Auroras
M. Fukizawa; T. Sakanoi; Y. Ogawa; T. T. Tsuda; K. Hosokawa
Journal of Geophysical Research: Space Physics, 126, 12, Dec. 2021, Pulsating auroras (PsAs) are considered to be caused by energetic (>a few keV) electron precipitation. Additionally, soft electron precipitation (Scientific journal - Simultaneous Pulsating Aurora and Microburst Observations With Ground-Based Fast Auroral Imagers and CubeSat FIREBIRD-II
Miki Kawamura; Takeshi Sakanoi; Mizuki Fukizawa; Yoshizumi Miyoshi; Keisuke Hosokawa; Fuminori Tsuchiya; Yuto Katoh; Yasunobu Ogawa; Kazushi Asamura; Shinji Saito; Harlan Spence; Arlo Johnson; Shin'ichiro Oyama; Urban Brandstrom
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 48, 18, Sep. 2021, We report on the relationship between a pulsating aurora and a relativistic electron microburst using simultaneous observations of ground-based fast auroral imagers with the FIREBIRD-II CubeSat for the first time. We conducted a detailed analysis of an event on October 8, 2018 and found that the occurrence of the pulsating aurora with internal modulations corresponds to the flux enhancement of electrons with energy ranging from similar to 220 keV to >1 MeV detected with Flight Unit 4, one of FIREBIRD's CubeSat, with a time delay of similar to 585 ms. Combining of this time delay result and time of flight model, we suggest that the pulsating aurora and the microburst occur simultaneously due to the chorus waves at different latitudes along the same field-line as predicted by Miyoshi et al. (2020, ).
Scientific journal, English - Dayside Cusp Aurorae and Ionospheric Convection Under Radial Interplanetary Magnetic Fields
Li; Hsien-Ming, Shue; Jih-Hong, Taguchi; Satoshi, Nose; Masahito; Hosokawa; Keisuke, Ruohoniemi; J. Michael; Zhang, Yongliang; Wing, Simon; Lester, Mark
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 126, 5, May 2021, Peer-reviwed
Scientific journal, English - Editorial: Special Issue: "SuperDARN / Studies of Geospace Dynamics - Today and Future"
Akira Sessai Yukimatu; Adrian Grocott; Evan G. Thomas; Tsutomu Nagatsuma; Nozomu Nishitani; Keisuke Hosokawa; Masakazu Watanabe
Polar Science, Elsevier BV, 100690-100690, May 2021
Scientific journal - Horizontal movement of polar mesospheric clouds observed from the Himawari-8 geostationary meteorological satellite
Hozumi, Y; Tsuda, T. T; Hosokawa, K; Ando, Y; Suzuki, H; Murata, T; Nakamura, T
Journal of Geophysical Research, 126, doi:10.1029/2021JD035081, 2021, Peer-reviwed
Scientific journal, English - Periodicities and colors of pulsating auroras: DSLR camera observations from the International Space Station
Nanjo, S; Hozumi, Y; Hosokawa, K; Kataoka, R; Miyoshi, Y; Oyama, S.-I
Journal of Geophysical Research, 126, doi:10.1029/2021JA029564, 2021, Peer-reviwed
Scientific journal, English - Software-defined radio-based HF doppler receiving system
Nakata, H; K. Nozaki; Y. Oki; K. Hosokawa; K. K. Hashimoto; T. Kikuchi; J. Sakai; I. Tomizawa; S. Saita
Earth, Planets and Space, Springer Science and Business Media LLC, 73, 1, doi:10.1186/s40623-021-01547-5, 2021, Peer-reviwed, Abstract
High-frequency Doppler (HFD) sounding is one of the major remote sensing techniques used for monitoring the ionosphere. Conventional systems for HFDs mainly utilize analog circuits. However, existing analog systems have become difficult to maintain as the number of people capable of working with analog circuits has declined. To solve this problem, we developed an alternate HFD receiver system based on digital signal processing. The software-defined radio (SDR) technique enables the receiver to be set up without the knowledge of analog circuit devices. This approach also downsizes the system and reduces costs. A highly stabilized radio system for both the transmitter and receiver is necessary for stable long-term observations of various phenomena in the ionosphere. The global positioning system disciplined oscillator with an accuracy of $${10}^{-11}$$ compensates for the frequency stability required by the new receiving system. In the new system, four frequencies are received and signal-processed simultaneously. The dynamic range of the new system is wider (> 130 dB) than that of the conventional system used in HFD observations conducted by the University of Electro-Communications in Japan. The signal-to-noise ratio significantly improved by 20 dB. The new digital system enables radio waves to be received with much smaller amplitudes at four different frequencies. The new digital receivers have been installed at some of the stations in the HFD observation network in Japan and have already captured various ionospheric phenomena, including medium-scale traveling ionospheric disturbances and sudden commencement induced electric field fluctuations, which indicates the feasibility of SDR for actual ionospheric observations. The new digital receiver is simple, inexpensive, and small in size, which makes it easy to deploy new receiving stations in Japan and elsewhere. These advantages of the new system will help drive the construction of a wide HFD observation network.
Graphical Abstract
Scientific journal, English - Auroral heating of plasma patches due to high-latitude reconnection
Díaz Pena, J; J. Semeter; Y. Nishimura; R. Varney; A. Reimer; M. Hairston; M. Zettergren; M. Hirsch; O. Verkhoglyadova; K. Hosokawa; K. Shiokawa
Journal of Geophysical Research, 126, doi:10.1029/2021JA029657, 2021, Peer-reviwed
Scientific journal, English - Penetration of the electric fields of the geomagnetic sudden commencement over the globe as observed with the HF Doppler sounders and magnetometers
Kikuchi, T; J. Chum; I. Tomizawa; K. K. Hashimoto; K. Hosokawa; Y. Ebihara; K. Hozumi; P. Supnithi
Earth Planets Space, 73, 10, ---, 2021, Peer-reviwed
Scientific journal, English - Magnetic conjugacy of Pc1 waves and isolated proton precipitation at subauroral latitudes: Importance of ionosphere as intensity modulation region
Ozaki, M; K. Shiokawa; R. B. Horne; M. J. Engebretson; M. Lessard; Y. Ogawa; K. Hosokawa; M. Nosé; Y. Ebihara; A. Kadokura; S. Yagitani; Y. Miyoshi; S. Hashimoto; S. S. Ashwini; K. S. Gopi; K. Seemala; C.-W. Jun
Geophysical Research Letters, AMER GEOPHYSICAL UNION, 48, 5, ---, 2021, Peer-reviwed, Pc1 geomagnetic pulsations, equivalent to electromagnetic ion cyclotron waves in the magnetosphere, display a specific amplitude modulation, though the region of the modulation remains an open issue. To classify whether the amplitude modulation has a magnetospheric or ionospheric origin, an isolated proton aurora (IPA), which is a proxy of Pc1 wave-particle interactions, is compared with the associated Pc1 waves for a geomagnetic conjugate pair, Halley Research Base in Antarctica and Nain in Canada. The temporal variation of an IPA shows a higher correlation coefficient (0.88) with Pc1 waves in the same hemisphere than that in the opposite hemisphere. This conjugate observation reveals that the classic cyclotron resonance is insufficient to determine the amplitude modulation. We suggest that direct wave radiation from the ionospheric current by IPA should also contribute to the amplitude modulation.
Scientific journal, English - Visualizing sporadic E using aeronautical navigation signals at VHF frequencies
Hosokawa, K; K., Kimura; J. Sakai; S. Saito; I. Tomizawa; M. Nishioka; T. Tsugawa; M. Ishii
Journal of Space Weather and Space Climate, 11, 6, ---, 2021, Peer-reviwed
Scientific journal, English - Plasma sheet thinning due to loss of near-Earth magnetotail plasma
Tretler, R; T. Tatsuno; K. Hosokawa
Journal of Plasma Physics, 87, 10, ---, 2021, Peer-reviwed
Scientific journal, English - Energy-resolved detection of precipitating electrons of 30–100 keV by a sounding rocket associated with dayside chorus waves
Sugo, S; O. Kawashima; S. Kasahara; K. Asamura; R. Nomura; Y. Miyoshi; Y. Ogawa; K. Hosokawa; T. Mitani; T. Namekawa; T. Sakanoi; M. Fukizawa; N. Yagi; Y. Fedorenko; A. Nikitenko; S. Yokota; K. Keika; T. Hori; C. Koehler
Journal of Geophysical Research, 126, -, ---, 2021, Peer-reviwed, Whistler mode chorus waves scatter magnetospheric electrons and cause precipitation into the Earth's atmosphere. Previous measurements showed that nightside chorus waves are indeed responsible for diffuse/pulsating aurora. Although chorus waves and electron precipitation have also been detected on the dayside, their link has not been illustrated (or demonstrated) in detail compared to the nightside observations. Conventional low-altitude satellite observations do not well resolve the energy range of 10–100 keV, hampering verification on resonance condition with chorus waves. In this paper we report observations of energetic electrons with energies of 30–100 keV that were made by the electron sensor installed on the NASA's sounding rocket RockSat-XN. It was launched from the Andøya Space Center on the dayside (MLT ∼ 11 h) at the L-value of ∼7 on January 13, 2019. Transient electron precipitation was observed at ∼50 keV with the duration of <100 s. The VLF receiver of a ground station at Kola peninsula in Russia near the rocket's footprint observed intermittent emissions of whistler-mode waves at the VLF frequency range simultaneously with the rocket observations. The energy of precipitating electrons is consistent with those derived from the quasilinear theory of pitch angle scattering by chorus waves through cyclotron resonance, assuming a typical dayside magnetospheric electron density. Precise interaction region is discussed based on the obtained energy spectrum below 100 keV.
Scientific journal, English - Over-darkening of pulsating aurora
Hosokawa, K; Y. Miyoshi; S.-I. Oyama; Y. Ogawa; S. Kurita; Y. Kasahara; Y. Kasaba; S. Yagitani; S. Matsuda; M. Ozaki; F. Tsuchiya; A. Kumamoto; T. Takashima; I. Shinohara; R. Fujii
Journal of Geophysical Research, 126, -, ---, 2021, Peer-reviwed, Recent analyses of high-time resolution ground-based optical observations of pulsating aurora (PsA) have reported that the brightness of PsA sometimes decreases below the diffuse background level immediately after the ON phase of the main pulsation finishes. To date, however, the generation mechanism of such an “over-darkening PsA” is still unclarified. In this study, we investigated the characteristics of the over-darkening PsA by using simultaneous observations of PsA with an electron multiplying charge coupled device all-sky camera in Sodankylä, Finland and the Arase satellite. During one of the conjunction events in Scandinavia on March 29, 2017, almost all the PsA pulses showed clear over-darkening characteristics. By analyzing the 2D all-sky images at the times of over-darkening we discovered that over-darkening areas appeared in the trailing edge of PsA patches and moved in tandem with the poleward propagating patches. It was also found that similar over-decreasing characteristics were not seen in the chorus data from the wave instruments onboard Arase located at the magnetospheric counterpart of PsA. These results indicate that the over-darkening PsA is not caused by a temporal variation of chorus at a fixed point, but is produced by a propagation of over-darkening area with PsA patches. That is, the over-darkening PsA is a result of compounding effects of spatial structure and recurrent propagation of PsA. The mechanism creating the dark area is still unknown, but the existence of over-darkening PsA suggests that the temporal variation of PsA is not always a perfect copy of the modulation of lower-band chorus waves in the magnetosphere.
Scientific journal, English - What controls the luminosity of polar cap airglow patches?: Implication from airglow measurements in Eureka, Canada in comparison with SuperDARN convection pattern
Hosokawa, K; M. Nagata; K. Shiokawa; Y. Otsuka
Polar Science, 28, -, ---, 2021, Peer-reviwed
Scientific journal, English - Spatial Evolution of Wave-Particle Interaction Region Deduced From Flash-Type Auroras and Chorus-Ray Tracing
Mitsunori Ozaki; Tomohiro Inoue; Yoshimasa Tanaka; Satoshi Yagitani; Yoshiya Kasahara; Kazuo Shiokawa; Yoshizumi Miyoshi; Kousuke Imamura; Keisuke Hosokawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 126, 7, 10.1029/2021JA029254, 2021, Peer-reviwed, In-situ observations of spatial variations of the wave-particle interaction region require a large number of satellite probes. As an alternative, flash-type auroras, a kind of pulsating aurora, driven by discrete chorus elements, can be used to investigate the interaction region with a high spatial resolution. We estimated the spatial extent of wave-particle interaction region from ground-based observations of flash aurora at Gakona (62.39 degrees N, 214.78 degrees E), Alaska at subauroral latitudes, and found that the auroral expansion was predominantly to the low-latitude side. The spatial displacement is thought to be caused by the propagation effects of chorus waves in the magnetosphere. Using ray tracing analysis to take into account chorus wave propagation, we reconstructed the spatiotemporal evolution of the volume emission rate and confirmed that the predominant expansion is toward the lower-latitude side in the ionosphere. This study shows that chorus wave propagation in the magnetosphere gives new insight for characterizing the transverse size (across the geomagnetic field line) of wave-particle interaction regions. The calculated spatial scale of the column auroral emission shows a correlation with the magnetic latitude of the resonance region at magnetic latitudes within 10 degrees of the equatorial plane of the magnetosphere. Our results suggest that the spatial scale of a flash aurora is indirectly related to the chorus amplitude because the latitudinal range of the wave-particle interaction is important for the growth of wave amplitude.
Scientific journal, English - Rocket Observation of Sub-Relativistic Electrons in the Quiet Dayside Auroral Ionosphere
T. Namekawa; T. Mitani; K. Asamura; Y. Miyoshi; K. Hosokawa; Y. Ogawa; S. Saito; T. Hori; S. Sugo; O. Kawashima; S. Kasahara; R. Nomura; N. Yagi; M. Fukizawa; T. Sakanoi; Y. Saito; A. Matsuoka; I. Shinohara; Y. Fedorenko; A. Nikitenko; C. Koehler
Journal of Geophysical Research, American Geophysical Union (AGU), 126, 7, 10.1029/2020JA, 2021, Peer-reviwed
Scientific journal, English - Penetration of MeV electrons into the mesosphere accompanying pulsating aurorae
Y. Miyoshi; K. Hosokawa; S. Kurita; S.-I. Oyama; Y. Ogawa; S. Saito; I. Shinohara; A. Kero; E. Turunen; P. T. Verronen; S. Kasahara; S. Yokota; T. Mitani; T. Takashima; N. Higashio; Y. Kasahara; S. Matsuda; F. Tsuchiya; A. Kumamoto; A. Matsuoka; T. Hori; K. Keika; M. Shoji; M. Teramoto; S. Imajo; C. Jun; S. Nakamura
Scientific Reports, Springer Nature, 11, 11, 2021, Peer-reviwed, Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.
Scientific journal, English - PSTEP: project for solar–terrestrial environment prediction
Kanya Kusano; Kiyoshi Ichimoto; Mamoru Ishii; Yoshizumi Miyoshi; Shigeo Yoden; Hideharu Akiyoshi; Ayumi Asai; Yusuke Ebihara; Hitoshi Fujiwara; Tada-Nori Goto; Yoichiro Hanaoka; Hisashi Hayakawa; Keisuke Hosokawa; Hideyuki Hotta; Kornyanat Hozumi; Shinsuke Imada; Kazumasa Iwai; Toshihiko Iyemori; Hidekatsu Jin; Ryuho Kataoka; Yuto Katoh; Takashi Kikuchi; Yûki Kubo; Satoshi Kurita; Haruhisa Matsumoto; Takefumi Mitani; Hiroko Miyahara; Yasunobu Miyoshi; Tsutomu Nagatsuma; Aoi Nakamizo; Satoko Naka
Earth, Planets, Space, SPRINGER, -, -, 2021, Peer-reviwed, Although solar activity may significantly impact the global environment and socioeconomic systems, the mechanisms for solar eruptions and the subsequent processes have not yet been fully understood. Thus, modern society supported by advanced information systems is at risk from severe space weather disturbances. Project for solar-terrestrial environment prediction (PSTEP) was launched to improve this situation through synergy between basic science research and operational forecast. The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. By this project, we sought to answer the fundamental questions concerning the solar-terrestrial environment and aimed to build a next-generation space weather forecast system to prepare for severe space weather disasters. The PSTEP consists of four research groups and proposal-based research units. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.
Scientific journal, English - Variations in Cosmic Noise Absorption in Association With Equatorward Development of the Pulsating Auroral Patch: A Case Study to Estimate the Energy Spectra of Auroral Precipitating Electrons
Taishiro Miyamoto; Shin-ichiro Oyama; Tero Raita; Keisuke Hosokawa; Yoshizumi Miyoshi; Yasunobu Ogawa; Satoshi Kurita
Journal of Geophysical Research, AMER GEOPHYSICAL UNION, 126, 9, 10.1029/2021JA029309, 2021, Peer-reviwed, This study focused on a pulsating aurora event associated with aurora morphological changes in Fennoscandia in the early morning on March 7, 2017. A high-speed sampling all-sky camera captured equatorward development of the pulsating auroral patch in association with a substorm centered over the Greenland/North America region. Of particular interest in this event is the interconnection between the auroral intensity and the cosmic noise absorption (CNA) derived from three riometers aligned meridionally in Finland (from north to south: Ivalo, Sodankyla, and Rovaniemi). The analysis was made by dividing optical measurements into two oscillation components: longer and shorter than 40 s, that is, nonpulsating and pulsating auroral modulations. The interrelation between the auroral brightness and CNA showed a linear correlation. The inclination of the regression line changed with time depending on latitudes, which was interpreted as hardening or softening of the precipitating electron spectrum. Especially in the case of the low-pass component, the inclination of the CNA-vs-intensity interrelation increased at the three riometer latitudes in the substorm recovery phase. On the other hand, for the high-pass component, the inclination decreased at Rovaniemi (lower latitude) but remained uniform at Sodankyla (higher latitude). These features suggest that the precipitating electron spectrum has softened in the low-pass or nonpulsating auroral component, but the spectrum has hardened in the high-pass or pulsating auroral component on the lower latitude part of the auroral patch region. This study proposes a new application of riometer-camera measurements to examine auroral particle precipitation.
Scientific journal, English - Occurrence distribution of polar cap patches: dependences on UT, season and hemisphere
Kagawa, A; Hosokawa, K; Ogawa, Y; Ebihara, Y; Kadokura
Journal of Geophysical Research, 126, 1, doi:10.1029/2020JA028538, 2021, Peer-reviwed, Polar cap patches are islands of enhanced electron density in the polar cap F region ionosphere, which sometimes affect the propagation of trans-ionospheric radio waves. Considering the intake of daytime sunlit plasma by the high-latitude convection as the primary cause of patches, the spatial overlap between the convection and the daytime sunlit plasma should be one of the critical factors controlling the generation of patches. To confirm this hypothesis, we statistically investigated the UT and seasonal distributions of patch occurrence frequency in both the hemispheres by using in situ plasma density data from the Swarm satellite. As a result, it was found that the occurrence distribution of patches is a complex function of UT, season and hemisphere, but it can be mostly interpreted by the spatial overlap between the high-latitude convection and the solar terminator. This suggests that polar cap patches are not necessarily phenomena that occur only during winter months. That is, patches can often be observed even in periods away from the winter solstice if the location of solar terminator in the magnetic coordinate system is appropriate for the generation of patches. For example, in the southern hemisphere, where the offset between the geographic and magnetic poles is larger than that in the northern hemisphere, the highest patch occurrence rate is obtained around the equinoctial periods. These results indicate that it is needed to take these dependences into account when we discuss and predict the space weather impacts of patches on the trans-ionospheric radio propagation.
Scientific journal, English - The Quasipersistent Feature of Highly Structured Field‐Aligned Currents in the Duskside Auroral Oval: Conjugate Observation Via Swarm Satellites and a Ground All‐Sky Imager
Y. Yokoyama; S. Taguchi; T. Iyemori; K. Hosokawa
Journal of Geophysical Research: Space Physics, American Geophysical Union (AGU), 125, 7, Jul. 2020, Peer-reviwed
Scientific journal - Asymmetric Development of Auroral Surges in the Northern and Southern Hemispheres
Herbert Akihito Uchida; Ryuho Kataoka; Akira Kadokura; Kiyoka Murase; Akira Sessai Yukimatu; Yoshizumi Miyoshi; Kazuo Shiokawa; Yusuke Ebihara; Keisuke Hosokawa; Ayako Matsuoka; S. Kurita; Shigeru Fujita; I. Shinohara
Geophys. Res. Lett., 47, Jun. 2020, Peer-reviwed, True
Scientific journal, English - Development of low-cost multi-wavelength imager system for studies of aurora and airglow
Y. Ogawa; Y. Tanaka; A. Kadokura; K. Hosokawa; Y. Ebihara; T. Motoba; B. Gustavsson; U. Brändström; Y. Sato; S. Oyama; M. Ozaki; T. Raita; F. Sigernes; S. Nozawa; K. Shiokawa; M. Kosch; K. Kauristie; C. Hall; S. Suzuki; Y. Miyoshi; A. Gerrard; H. Miyaoka; R. Fujii
Polar Science, Mar. 2020, Peer-reviwed, © 2019 Elsevier B.V. and NIPR This paper introduces a new system that can monitor aurora and atmospheric airglow using a low-cost Watec monochromatic imager (WMI) equipped with a sensitive camera, a filter with high transmittance, and the non-telecentric optics. The WMI system with 486-nm, 558-nm, and 630-nm band-pass filters has observable luminosity of about ~200–4000 Rayleigh for 1.07-sec exposure time and about ~40–1200 Rayleigh for 4.27-sec exposure time, for example. It is demonstrated that the WMI system is capable of detecting 428-nm auroral intensities properly, through comparison with those measured with a collocated electron-multiplying charge-coupled device (EMCCD) imager system with narrower band-pass filter. The WMI system has two distinct advantages over the existing system: One makes it possible to reduce overall costs, and the other is that it enables the continuous observation even under twilight and moonlight conditions. Since 2013 a set of multi-wavelength WMIs has been operating in northern Scandinavia, Svalbard, and Antarctica to study meso- and large-scale aurora and airglow phenomena. Future development of the low-cost WMI system is expected to provide a great opportunity for constructing a global network for multi-wavelength aurora and airglow monitoring.
Scientific journal - Multiple time-scale beats in aurora: precise orchestration via magnetospheric chorus waves
K. Hosokawa; Y. Miyoshi; M. Ozaki; S. I. Oyama; Y. Ogawa; S. Kurita; Y. Kasahara; Y. Kasaba; S. Yagitani; S. Matsuda; F. Tsuchiya; A. Kumamoto; R. Kataoka; K. Shiokawa; T. Raita; E. Turunen; T. Takashima; I. Shinohara; R. Fujii
Scientific reports, 10, 1, 3380, 25 Feb. 2020, Peer-reviwed, The brightness of aurorae in Earth's polar region often beats with periods ranging from sub-second to a few tens of a second. Past observations showed that the beat of the aurora is composed of a superposition of two independent periodicities that co-exist hierarchically. However, the origin of such multiple time-scale beats in aurora remains poorly understood due to a lack of measurements with sufficiently high temporal resolution. By coordinating experiments using ultrafast auroral imagers deployed in the Arctic with the newly-launched magnetospheric satellite Arase, we succeeded in identifying an excellent agreement between the beats in aurorae and intensity modulations of natural electromagnetic waves in space called "chorus". In particular, sub-second scintillations of aurorae are precisely controlled by fine-scale chirping rhythms in chorus. The observation of this striking correlation demonstrates that resonant interaction between energetic electrons and chorus waves in magnetospheres orchestrates the complex behavior of aurora on Earth and other magnetized planets.
Scientific journal - Observations of equatorial plasma bubbles using a low-cost 630.0-nm all-sky imager in Ishigaki Island, Japan
Hosokawa, K; K. Takami; S. Saito; Y. Ogawa; Y. Otsuka; K. Shiokawa; C.-H. Chen; C.-H. Lin
Earth, Planets and Space, 72, 1, doi:10.1186/s40623-020-01187-1, 2020, Peer-reviwed, © 2020, The Author(s). Here, we introduce a low-cost airglow imaging system developed for observing plasma bubble signatures in 630.0-nm airglow emission from the F region of the ionosphere. The system is composed of a small camera, optical filter, and fish-eye lens, and is operated using free software that automatically records video from the camera. A pilot system was deployed in Ishigaki Island in the southern part of Japan (Lat 24.4, Lon 124.4, Mlat 19.6) and was operated for ~ 1.5 years from 2014 to 2016 corresponding to the recent solar maximum period. The pilot observations demonstrated that it was difficult to identify the plasma bubble signature in the raw image captured every 4 s. However, the quality of the image could be improved by reducing the random noise of instrumental origin through an integration of 30 consecutive raw images obtained in 2 min and further by subtracting the 1-h averaged background image. We compared the deviation images to those from a co-existing airglow imager of OMTIs, which is equipped with a back-illuminated cooled CCD camera with a high quantum efficiency of ~ 90%. It was confirmed that the low-cost airglow imager is capable of imaging the spatial structure of plasma bubbles, including their bifurcating traces. The results of these pilot observations in Ishigaki Island will allow us to distribute the low-cost imager in a wide area and construct a network for monitoring plasma bubbles and their space weather impacts on satellite navigation systems.[Figure not available: see fulltext.].
Scientific journal, English - Penetration electric fields observed at middle and low latitudes during the 22 June 2015 geomagnetic storm
Hashimoto K. K; T. Kikuchi; I. Tomizawa; K. Hosokawa; J. Chum; D. Buresova; M. Nose; K. Koga
Earth, Planets and Space, Springer Science and Business Media LLC, 72, 1, doi:10.1186/s40623-020-01196-0, 2020, Peer-reviwed
Scientific journal, English - A monitoring network for anomalous propagation of aeronautical VHF radio waves due to sporadic E in Japan
Hosokawa, K; J. Sakai; I. Tomizawa; S. Saito; T. Tsugawa; M. Nishioka; M. Ishii
Earth, Planets and Space, 72, doi:10.1186/s40623-020-01216-z, 2020, Peer-reviwed
Scientific journal, English - Estimation of the emission altitude of pulsating aurora using the five-wavelength photometer
Kawamura, Y; K. Hosokawa; S. Nozawa; Y. Ogawa; T. Kawabata; S.-I. Oyama; Y. Miyoshi; S. Kurita; R. Fujii
Earth, Planets and Space, Springer Science and Business Media LLC, 72, 1, doi:10.1186/s40623-020-01229-8, 2020, Peer-reviwed
Scientific journal, English - Loss of the Rarefaction Wave during Plasma Sheet Thinning
Tretler, R; T. Tatsuno; K. Hosokawa
Plasma and Fusion Research, 15, doi:10.1585/pfr.15.2401053, 2020, Peer-reviwed
Scientific journal, English - Arase observation of the source region of auroral arcs and diffuse auroras in the inner magnetosphere
Shiokawa, K; M. Nose; S. Imajo; Y. Tanaka; Y. Miyoshi; K. Hosokawa; M. Connors; M. Engebretson; Y. Kazama; S.-Y. Wang; S. W; Y. Tam; Tzu-Fang Chang; Bo-Jhou Wang; K. Asamura; S. Kasahara; S. Yokota; T. Hori; K. Keika; Y. Kasaba; M. Shoji; Y. Kasahara; A. Matsuoka; I. Shinohara
Journal of Geophysical Research, American Geophysical Union (AGU), 125, 8, doi:10.1029/2019JA027310, 2020, Peer-reviwed
Scientific journal, English - Anomalous propagation of radio waves from distant ILS localizers due to ionospheric sporadic‐E
Sakai, J; Saito, S; Hosokawa, K; Tomizawa, I
Space Weather, 18, doi:10.1029/2020SW002517, 2020, Peer-reviwed
Scientific journal, English - Plasma waves causing relativistic electron precipitation events at International Space Station: Lessons from conjunction observations with Arase satellite
Kataoka, R; Y. Asaoka; S. Torii; S. Nakahira; H. Ueno; S. Miyake; Y. Miyoshi; S. Kurita; M. Shoji; Y. Kasahara; M. Ozaki; S. Matsuda; A. Matsuoka; Y. Kasaba; I. Shinohara; K. Hosokawa; H. A. Uchida; K. Murase; Y. Tanaka
Journal of Geophysical Research, AMER GEOPHYSICAL UNION, 125, 9, doi:10.1029/2020JA027875, 2020, Peer-reviwed, We report three different types of relativistic electron precipitation (REP) events observed at International Space Station (ISS), associated with electromagnetic ion cyclotron (EMIC) waves or whistler mode waves as observed by the Arase satellite at conjugate locations near the magnetic equator. Three different detectors installed on the ISS were complementarily used; CALET/CHD as the detector of precipitating MeV electrons, MAXI/RBM as the detector of sub-MeV electrons from horizontal and vertical directions, and SEDA-AP/SDOM to quantitatively measure the energy spectrum. The REP event on 21 August 2017 shows a quasiperiodic intensity variation at similar to 1 Hz which corresponds to variations of the EMIC waves at the Arase altitudes. The REP event on 24 April 2017 shows rapid and irregular intensity variation which corresponds to the amplitude variation of chorus waves, while the REP events on 26 October 2017 shows a smooth quasiperiodic time variation at similar to 0.2 Hz which corresponds to the amplitude variation of "electrostatic" whistler mode waves. This study clearly demonstrates that the time variation of REP events at ISS are caused by various types of plasma waves near the magnetic equator.
Scientific journal, English - Relativistic Electron Microbursts as High Energy Tail of Pulsating Aurora Electrons
Miyoshi, Y; Saito, S; Kurita, S; Asamura, K; Hosokawa, K; Sakanoi, T
Geophysical Research Letters, American Geophysical Union (AGU), 47, 21, doi:10.1029/2020GL090360, 2020, Peer-reviwed
Scientific journal, English - OI 630.0‐nm and N2 1PG emissions in pulsating aurora events observed by an optical spectrograph at Tromsø, Norway
Tsuda, T. T; Li, C; Hamada, S; Hosokawa, K; Oyama, S.‐i; Nozawa, S
Journal of Geophysical Research, American Geophysical Union (AGU), 125, 12, doi:10.1029/2020JA028250, 2020, Peer-reviwed
Scientific journal, English - Aurora in the Polar Cap: A Review
Hosokawa, K; A. Kullen; S. Milan; J. Reidy; Y. Zou; H. Frey; R. Maggiolo; R. Fear
Space Science Review, 216, doi:10.1007/s11214-020-0637-3, 2020, Peer-reviwed
Scientific journal, English - Fine-scale visualization of aurora in a wide area using color digital camera images from the International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Journal of Geophysical Research, American Geophysical Union (AGU), 125, 3, doi:10.1029/2019JA027729, 2020, Peer-reviwed
Scientific journal, English - Multi-instrument Observations of Ion-Neutral Coupling in the Dayside Cusp
Billett, D. D.; K. Hosokawa; A. Grocott; J. A. Wild; A. L. Aruliah; Y. Ogawa; S. Taguchi
Geophysical Research Letters, Jan. 2020, Peer-reviwed - Imaging of polar cap patches with a low-cost airglow camera: Pilot observations in Svalbard, Norway
K. Hosokawa; Y. Ogawa; S. Taguchi
Earth, Planets and Space, EPSP-D-19-00160, 71, Nov. 2019, Peer-reviwed - Direct Comparison Between Magnetospheric Plasma Waves and Polar Mesosphere Winter Echoes in Both Hemispheres
Y.-M. Tanaka; T. Nishiyama; A. Kadokura; M. Ozaki; Y. Miyoshi; K. Shiokawa; S.-I. Oyama; R. Kataoka; M. Tsutsumi; K. Nishimura; K. Sato; Y. Kasahara; A. Kumamoto; F. Tsuchiya; M. Fukizawa; M. Hikishima; S. Matsuda; A. Matsuoka; I. Shinohara; M. Nosé; T. Nagatsuma; M. Shinohara; A. Fujimoto; M. Teramoto; R. Nomura; A. Sessai Yukimatu; K. Hosokawa; M. Shoji; R. Latteck
Journal of Geophysical Research: Space Physics, 124, 9626-9639, 10 Oct. 2019, Peer-reviwed - Spatiotemporal development of pulsating auroral patch associated with discrete chorus elements: Arase and PWING observations
Ozaki, M; K. Shiokawa; Y. Miyoshi; K. Hosokawa; S. Oyama; S. Yagitani; Y. Kasahara; Y. Kasaba; S. Matsuda; R. Kataoka; Y. Ebihara; Y. Ogawa; Y. Otsuka; S. Kurita; R. C. Moore; Y.-M. Tanaka; M. Nosé; T. Nagatsuma; M. Connors; N. Nishitani; M. Hikishima; A. Kumamoto; F. Tsuchiya; A. Kadokura; T. Nishiyama; T. Inoue; K. Imamura; A. Matsuoka; I. Shinohara
2019 URSI ASIA-PACIFIC RADIO SCIENCE CONFERENCE (AP-RASC), 18776063, Jun. 2019, Peer-reviwed
International conference proceedings, English - Velocity Rotation Events in the Outer Magnetosphere Near the Magnetopause
Matsui, H; C.J. Farrugia; J. Goldstein; R. B. Torbert; M. R. Argall; H. Vaith; C. T. Russell; R. J; Strangeway; B. L. Giles; C. J. Pollock; S. Taguchi; K. Hosokawa
Journal of Geophysical Research Space Physics, 124, May 2019
Scientific journal, English - Geographical and Seasonal Variability of Mesospheric Bores Observed from the International Space Station
Hozumi Yuta; Saito Akinori; Sakanoi Takeshi; Yamazaki Atsushi; Hosokawa Keisuke; Nakamura Takuji
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 124, 5, 3775-3785, May 2019, Peer-reviwed - Polarization electric field inside auroral patches: Simultaneous experiment of EISCAT radars and KAIRA
Takahashi, T; I. Virtanen; K. Hosokawa; Y. Ogawa; A. Aikio; H. Miyaoka; A. Kero
J. Geophys. Res., American Geophysical Union ({AGU}), 10.1029/2018JA026254, 5, 3543-3557, May 2019, Peer-reviwed - Visualization of rapid electron precipitation via chorus element wave-particle interactions.
Mitsunori Ozaki; Yoshizumi Miyoshi; Kazuo Shiokawa; Keisuke Hosokawa; Shin-Ichiro Oyama; Ryuho Kataoka; Yusuke Ebihara; Yasunobu Ogawa; Yoshiya Kasahara; Satoshi Yagitani; Yasumasa Kasaba; Atsushi Kumamoto; Fuminori Tsuchiya; Shoya Matsuda; Yuto Katoh; Mitsuru Hikishima; Satoshi Kurita; Yuichi Otsuka; Robert C Moore; Yoshimasa Tanaka; Masahito Nosé; Tsutomu Nagatsuma; Nozomu Nishitani; Akira Kadokura; Martin Connors; Takumi Inoue; Ayako Matsuoka; Iku Shinohara
Nature communications, 10, 1, 257-257, 16 Jan. 2019, Peer-reviwed, True, Chorus waves, among the most intense electromagnetic emissions in the Earth's magnetosphere, magnetized planets, and laboratory plasmas, play an important role in the acceleration and loss of energetic electrons in the plasma universe through resonant interactions with electrons. However, the spatial evolution of the electron resonant interactions with electromagnetic waves remains poorly understood owing to imaging difficulties. Here we provide a compelling visualization of chorus element wave-particle interactions in the Earth's magnetosphere. Through in-situ measurements of chorus waveforms with the Arase satellite and transient auroral flashes from electron precipitation events as detected by 100-Hz video sampling from the ground, Earth's aurora becomes a display for the resonant interactions. Our observations capture an asymmetric spatial development, correlated strongly with the amplitude variation of discrete chorus elements. This finding is not theoretically predicted but helps in understanding the rapid scattering processes of energetic electrons near the Earth and other magnetized planets.
Scientific journal, English - Tracking the region of high correlation between pulsating aurora and chorus: Simultaneous observations with Arase satellite and ground‐based all‐sky imager in Russia
Kawamura, S; K. Hosokawa; S. Kurita; S. Oyama; Y. Miyoshi; Y. Kasahara; M. Ozaki; S. Matsuda; A. Matsuoka; B. Kozelov; Y. Kawamura; I. Shinohara
Journal of Geophysical Research, 124, doi:10.1029/2019JA026496, 2019, Peer-reviwed
Scientific journal, English - A statistical study of anomalous VHF propagation due to the sporadic-E layer in the air-navigation band
Sakai, J; K. Hosokawa; I. Tomizawa; S. Saito
Radio Science, 54, 5, doi:10.1029/2018RS006781-439, 2019, Peer-reviwed, ©2019. American Geophysical Union. All Rights Reserved. The sporadic-E (Es) layer is an ionospheric layer which appears occasionally near 100-km heights with extremely high electron density. The Es layer may reflect very high-frequency radio signals when the incident angle is shallow (Es layer anomalous propagation [EsAP]). It is known that radio signals with frequencies above 100 MHz sometimes reach distant locations, more than 600 km apart from the transmitters, due to EsAP. Since air-navigation radio channels are allocated on frequencies between 108 and 118 MHz, EsAP may interfere with directly propagating wave (ground wave) signals. However, as the occurrence and strength of EsAP on these frequencies have not been studied well, it is difficult to assess the impact of EsAP on the air navigation. In this paper, we report the statistics of the occurrence and strength of EsAP based on a 3-year continuous monitoring of very high-frequency air-navigation radio signal strength on the ground. The statistics show that strong EsAPs occur frequently in summer. The occurrence pattern of EsAP is generally consistent with ionosonde observations of Es layer: Most Es layers appear during summer, primary peak in daytime, with a second peak in the evening. During an extreme EsAP event, in a particular channel, an EsAP signal was superposed on a ground wave signal which resulted in a fluctuation of ground wave signal by more than ±10 dB. Our statistical results suggest that the Es layer has a potential impact on air-navigation applications.
Scientific journal, English - Geographical and seasonal variability of mesospheric bores observed by IMAP/VISI
Hozumi, Y; A. Saito; T. Sakanoi; A. Yamazaki; K. Hosokawa; T. Nakamura
Journal of Geophysical Research, 124, doi:10.1029/2019JA026635, 2019, Peer-reviwed
Scientific journal, English - Airglow Patches in the Polar Cap Region: A Review
Hosokawa, K; Y. Zou; Y. Nishimura
Space Science Review, 215, doi:10.1007/s11214-019-0616-8, 2019, Peer-reviwed
Scientific journal, English - Diffuse and Pulsating Aurora
Nishimura, Y; M. R. Lessard; Y. Katoh; Y. Miyoshi; E. Grono; N. Partamies; N. Sivadas; K. Hosokawa; M. Fukizawa; M. Samara; R. G. Michell; R. Kataoka; T. Sakanoi; D. K. Whiter; S. Oyama; Y. Ogawa; S. Kurita
Space Science Reviews, in press, 2019, Peer-reviwed - Plasma flow in the north-south aligned auroral region equatorward of the dayside auroral oval
Taguchi, S; K. Hosokawa; Y. Ogawa
J. Geophys. Res., doi:10.1029/2019JA026895, in press, 2019, Peer-reviwed - Transient ionization of the mesosphere during auroral breakup: Arase satellite and ground-based conjugate observations at Syowa Station
Kataoka, R; T. Nishiyama; Y. -M. Tanaka; A. Kadokura; H. A. Uchida; Y. Ebihara; M. K. Ejiri; Y. Tomikawa; M. Tsutsumi; K. Sato; Y. Miyoshi; K. Shiokawa; S. Kurita; Y. Kasahara; M. Ozaki; K. Hosokawa; S. Matsuda; I. Shinohara; T. Takashima; T. Sato
Earth, Planet and Space, SPRINGEROPEN, 71, 9, Jan. 2019, Peer-reviwed, Transient mesospheric echo in the VHF range was detected at an altitude of 65-70km during the auroral breakup that occurred from 2220 to 2226 UT on June 30, 2017. During this event, the footprint of the Arase satellite was located within the field of view of the all-sky imagers at Syowa Station in the Antarctic. Auroral observations at Syowa Station revealed the dominant precipitation of relatively soft electrons during the auroral breakup. A corresponding spike in cosmic noise absorption was also observed at Syowa Station, while the Arase satellite observed a flux enhancement of >100keV electrons and a broadband noise without detecting chorus waves or electromagnetic ion cyclotron waves. A general-purpose Monte Carlo particle transport simulation code was used to quantitatively evaluate the ionization in the middle atmosphere. Results of this study indicate that the precipitation of energetic electrons of >100keV, rather than X-rays from the auroral electrons, played a dominant role in the transient and deep (65-70km) mesospheric ionization during the observed auroral breakup.
Scientific journal, English - Electrostatic Electron Cyclotron Harmonic Waves as a Candidate to Cause Pulsating Auroras
M. Fukizawa; T. Sakanoi; Y. Miyoshi; K. Hosokawa; K. Shiokawa; Y. Katoh; Y. Kazama; A. Kumamoto; F. Tsuchiya; Y. Miyashita; Y. M. Tanaka; Y. Kasahara; M. Ozaki; A. Matsuoka; S. Matsuda; M. Hikishima; S. Oyama; Y. Ogawa; S. Kurita; R. Fujii
Geophysical Research Letters, 45, 23, 12,661-12,668, 16 Dec. 2018, Peer-reviwed, ©2018. American Geophysical Union. All Rights Reserved. Pulsating auroras (PsAs) are thought to be generated by precipitating electrons scattered by lower-band chorus (LBC) waves near the magnetic equator. One-to-one correlation between the LBC intensity and the PsA intensity has been reported. Electrostatic electron cyclotron harmonic (ECH) waves can also scatter electrons. However, direct correlation between ECH and PsA has not been reported yet. In this study, using a coordinated Exploration of energization and Radiation in Geospace (Arase) satellite and ground-based imager observation, we report that not only LBC but also ECH have correlation with PsA. We estimated the precipitating electron energy by assuming that the time lag when the cross-correlation coefficient became the highest was travel time of electrons from the modulation region. We found that the estimated energies show reasonable values as the cyclotron resonance energy of each wave.
Scientific journal, English - A new five-wavelength photometer operated in TromsO (69.6 degrees N, 19.2 degrees E)
Nozawa Satonori; Kawabata Tetsuya; Hosokawa Keisuke; Ogawa Yasunobu; Tsuda Takuo; Mizuno Akira; Fujii Ryoichi; Hall Chris
EARTH PLANETS AND SPACE, 70, 11 Dec. 2018, Peer-reviwed - Auroral molecular-emission effects on the atomic oxygen line at 777.4 nm
Shin ichiro Oyama; Takuo T. Tsuda; Keisuke Hosokawa; Yasunobu Ogawa; Yoshizumi Miyoshi; Satoshi Kurita; Antti E. Kero; Ryoichi Fujii; Yoshimasa Tanaka; Akira Mizuno; Tetsuya Kawabata; Björn Gustavsson; Thomas Leyser
Earth, Planets and Space, 70, 1, 01 Dec. 2018, Peer-reviwed, © 2018, The Author(s). One of the representative auroral emission lines that radiates from F-region heights and is measurable on the ground is the 777.4 nm line from excited atomic oxygen. This line has been adopted, along with another E-region emission line, for example 427.8 nm, to estimate the mean energy and total energy flux of precipitating auroral electrons. The influence of emissions from part of the molecular nitrogen band, which mainly radiate from E-region heights, should be carefully evaluated because it might overlap the 777.4 nm atomic oxygen line in the spectrum. We performed statistical analysis of auroral spectrograph measurements that were obtained during the winter of 2016–2017 in Tromsø, Norway, to derive the ratio of the intensity of the 777.4 nm atomic oxygen line to that of the net measurement through a typically used optical filter with a full width at half maximum of a few nm. The ratio had a negative trend against geomagnetic activity, with a primary distribution of 0.5–0.7 and a minimum value of 0.3 for the most active auroral condition in this study. This result suggests that the 30–50% emission intensities measured through the optical filter may be from the molecular nitrogen band. [Figure not available: see fulltext.].
Scientific journal - A new five-wavelength photometer operated in Tromsø (69.6°N, 19.2°E)
Satonori Nozawa; Tetsuya Kawabata; Keisuke Hosokawa; Yasunobu Ogawa; Takuo Tsuda; Akira Mizuno; Ryoichi Fujii; Chris Hall
Earth, Planets and Space, 70, 1, 01 Dec. 2018, Peer-reviwed, © 2018, The Author(s). A new five-wavelength photometer was developed and installed at the EISCAT Tromsø site (69.6°N, 19.2°E) in January 2017. The photometer consists of two units: an optical unit and a control unit together with a PC. The photometer is capable of simultaneously observing auroral emissions with five wavelengths. A uniqueness of the present system is its capability of precise pointing, which enables pointing the photometer at the field-aligned position using a star image obtained with a coaxial digital camera. Another uniqueness of the system is its capability of taking data at a sampling rate of 400 Hz. Some preliminary results including correlations between 427.8 nm and 557.7 nm, 630 nm, 777.4 nm, and 844.6 nm are presented. These comparisons are not significant unless all of the five wavelength emissions emanated from exactly the same volume (i.e., magnetic zenith) in the ionosphere, which the present system has. [Figure not available: see fulltext.].
Scientific journal - Mesospheric bores at southern midlatitudes observed by ISS-IMAP/VISI: a first report of an undulating wave front
Hozumi Yuta; Saito Akinori; Sakanoi Takeshi; Yamazaki Atsushi; Hosokawa Keisuke
ATMOSPHERIC CHEMISTRY AND PHYSICS, 18, 22, 16399-16407, 19 Nov. 2018, Peer-reviwed - Microscopic Observations of Pulsating Aurora Associated With Chorus Element Structures: Coordinated Arase Satellite-PWING Observations
Ozaki, M; K. Shiokawa; Y. Miyoshi; K. Hosokawa; S. Oyama; S. Yagitani; Y. Kasahara; Y. Kasaba; S. Matsuda; R. Kataoka; Y. Ebihara; Y. Ogawa; Y. Otsuka; S. kurita; R. C. Moore; Y. -M. Tanaka; M. Nose; T. Nagatsuma; M. Connors; N. Nishitani; Y. Katoh; M. Hikishima; A. Kumamoto; F. Tsuchiya; A. Kadokura; T. Nishiyama; T. Inoue; K. Imamura; A. Matsuoka; I. Shinohara
Geophys. Res. Lett., 45, 22, Nov. 2018, Peer-reviwed
Scientific journal, English - Auroral molecular-emission effects on the atomic oxygen line at 777.4nm
Oyama Shin-ichiro; Tsuda Takuo T; Hosokawa Keisuke; Ogawa Yasunobu; Miyoshi Yoshizumi; Kurita Satoshi; Kero Antti E; Fujii Ryoichi; Tanaka Yoshimasa; Mizuno Akira; Kawabata Tetsuya; Gustavsson Bjorn; Leyser Thomas
EARTH PLANETS AND SPACE, 70, Oct. 2018, Peer-reviwed
English - Initial report on polar mesospheric cloud observations by Himawari-8
T. T. Tsuda; Y. Hozumi; K. Kawaura; K. Hosokawa; H. Suzuki; T. Nakamura
Atmos. Meas. Tech., 11, 6163-6168, 2018, Peer-reviwed
Scientific journal, English - Survey of conditions for artificial aurora experiments at EISCAT Tromsø using dynasonde data
Tsuda T. T; M. T. Rietveld; M. J. Kosch; S. Oyama; K. Hosokawa; S. Nozawa; T. Kawabata; A. Mizuno; Y. Ogawa
Earth, Planets and Space, 70, 40, doi:10.1186/s40623-018-0805-9, 2018, Peer-reviwed
Scientific journal, English - GPS amplitude and phase scintillation associated with polar cap auroral forms
P. T. Jayachandran; A. M. Hamza; K. Hosokawa; H. Mezaoui; K. Shiokawa
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 164, 185-191, Nov. 2017, Peer-reviwed, Global Positioning System (GPS) signal amplitude and phase scintillation occurrence were observed in close association with polar cap auroral forms. Scintillation were present on most GPS ray paths irrespective of the ray path's location and orientation relative to arc alignment, motion and the direction of E x B drift. Spectra of amplitude and phase scintillation show similar power law behaviour with close to identical power law coefficients. The distribution of power law coefficients shows an average power law coefficient of similar to-2.3, which is different from the spectral characteristics of equatorial and low latitude scintillation.
Scientific journal, English - Ground-based instruments of the PWING project to investigate dynamics of the inner magnetosphere at subauroral latitudes as a part of the ERG-ground coordinated observation network
Kazuo Shiokawa; Yasuo Katoh; Yoshiyuki Hamaguchi; Yuka Yamamoto; Takumi Adachi; Mitsunori Ozaki; Shin-Ichiro Oyama; Masahito Nose; Tsutomu Nagatsuma; Yoshimasa Tanaka; Yuichi Otsuka; Yoshizumi Miyoshi; Ryuho Kataoka; Yuki Takagi; Yuhei Takeshita; Atsuki Shinbori; Satoshi Kurita; Tomoaki Hori; Nozomu Nishitani; Iku Shinohara; Fuminori Tsuchiya; Yuki Obana; Shin Suzuki; Naoko Takahashi; Kanako Seki; Akira Kadokura; Keisuke Hosokawa; Yasunobu Ogawa; Martin Connors; J. Michael Ruohoniemi; Mark Engebretson; Esa Turunen; Thomas Ulich; Jyrki Manninen; Tero Raita; Antti Kero; Arto Oksanen; Marko Back; Kirsti Kauristie; Jyrki Mattanen; Dmitry Baishev; Vladimir Kurkin; Alexey Oinats; Alexander Pashinin; Roman Vasilyev; Ravil Rakhmatulin; William Bristow; Marty Karjala
EARTH PLANETS AND SPACE, SPRINGER HEIDELBERG, 69, Nov. 2017, Peer-reviwed, The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron volts (MeV). These plasmas rotate around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV, and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphere using ground-based network observations, http://www.isee.nagoya-u.ac.jp/dimr/PWING/) has been carried out since April 2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers, 64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at subauroral latitudes (similar to 60 degrees geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been developed as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations with the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will contribute to the investigation of dynamical variation of particles and waves in the inner magnetosphere, which is one of the most important research topics in recent space physics, and the outcome of our research will improve safe and secure use of geospace around the Earth.
Scientific journal, English - Statistical investigation of Na layer response to geomagnetic activity using resonance scattering measurements by Odin/OSIRIS
T. T. Tsuda; T. Nakamura; M. K. Ejiri; T. Nishiyama; K. Hosokawa; T. Takahashi; J. Gumbel; J. Hedin
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 44, 12, 5943-5950, Jun. 2017, Peer-reviwed, We have performed a statistical investigation of the global response of the Na layer to geomagnetic activity using Na density data from 2004 to 2010 obtained using the Optical Spectrograph and Infrared Imager System (OSIRIS) on board the Odin satellite. In the analysis, we categorized the Na density data according to the auroral electrojet (AE) index and then compared the resulting data sets. Regarding the results, we found a significant decrease in the Na density above a height of similar to 95 km in both the southern and northern polar regions with an increase in the AE index. The cause of the decrease in the Na density is discussed, and we conclude that the decrease in the Na density was mainly due to the effect of energetic particle precipitation.
Scientific journal, English - Horizontal profile of a moving red line cusp aurora
S. Taguchi; Y. Chiba; K. Hosokawa; Y. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 122, 3, 3509-3525, Mar. 2017, Peer-reviwed, Auroral emission at a wavelength of 630.0nm (red line) has a long radiative time. In this study, we show how this long radiative time controls the horizontal extent of a moving mesoscale aurora, which is typical of the cusp. Using high time resolution (4s) observations by an all-sky imager at Longyearbyen, Svalbard, and observations by the European Incoherent Scatter Svalbard Radar (ESR), we examined the auroral emission enhancements obtained in the cusp during an interval of southward interplanetary magnetic field on 27 November 2011. Simultaneous observations from the all-sky imager and the ESR clearly show the manner in which auroral emission regions passed through the radar's field of view. When the front edge of the moving auroral structure intersected the radar's field of view, the ESR electron temperature was enhanced. A few minutes later, the ESR electron temperature dropped to the background level, indicating that the mesoscale electron precipitation region shifted away from the radar's field of view. At that time, the auroral emission in the radar's field of view decreased but still had adequate intensities. These results provide evidence demonstrating that moving cusp auroral emission occurs behind the electron precipitation region as well as inside that region. We interpreted this feature semiquantitatively by using the equation of continuity of the density of the excited atomic oxygen. Our model indicates that the maximum intensity in the moving auroral structure occurs at a point along the trailing edge of the electron precipitation region and that the velocity of that region is important for determining how the 630.0 nm aurora emissions extend horizontally.
Scientific journal, English - Depletion of mesospheric sodium during extended period of pulsating aurora
T. Takahashi; K. Hosokawa; S. Nozawa; T. T. Tsuda; Y. Ogawa; M. Tsutsumi; Y. Hiraki; H. Fujiwara; T. D. Kawahara; N. Saito; S. Wada; T. Kawabata; C. Hall
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 122, 1, 1212-1220, 2017, Peer-reviwed, We quantitatively evaluated the Na density depletion due to charge transfer reactions between Na atoms and molecular ions produced by high-energy electron precipitation during a pulsating aurora (PsA). An extended period of PsA was captured by an all-sky camera at the European Incoherent Scatter (EISCAT) radar Tromso site (69.6 degrees N, 19.2 degrees E) during a 2 h interval from 00:00 to 02 00 UT on 25 January 2012. During this period, using the EISCAT very high frequency (VHF) radar, we detected three intervals of intense ionization below 100 km that were probably caused by precipitation of high-energy electrons during the PsA. In these intervals, the sodium lidar at Tromso observed characteristic depletion of Na density at altitudes between 97 and 100 km. These Na density depletions lasted for 8 min and represented 5-8% of the background Na layer. To examine the cause of this depletion, we modeled the depletion rate based on charge transfer reactions with NO+ and O-2(+) while changing the R value which is defined as the ratio of NO+ to O-2(+) densities, from 1 to 10. The correlation coefficients between observed and modeled Na density depletion calculated with typical value R=3 for time intervals T-1, T-2, and T-3 were 0.66, 0.80, and 0.67, respectively. The observed Na density depletion rates fall within the range of modeled depletion rate calculated with R from 1 to 10. This suggests that the charge transfer reactions triggered by the auroral impact ionization at low altitudes are the predominant process responsible for Na density depletion during PsA intervals.
Scientific journal, English - Periodic creation of polar cap patches from auroral transients in the cusp
K. Hosokawa; S. Taguchi; Y. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 121, 6, 5639-5652, Jun. 2016, Peer-reviwed, On 24 November 2012, an interval of polar cap patches was identified by an all-sky airglow imager located near the dayside cusp. During the interval, the successive appearance of poleward moving auroral forms (PMAFs) was detected, which are known to represent ionospheric manifestations of pulsed magnetic reconnections at the dayside magnetopause. All of the patches observed during the interval appeared from these transient auroral features (i.e., there was a one-to-one correspondence between PMAFs and newly created baby patches). This fact strongly suggests that patches can be directly and seamlessly created from a series of PMAFs. The optical intensities of the baby patches were 100-150 R, which is slightly lower than typical patch luminosity on the nightside and may imply that PMAF-induced patches are generally low density. The generation of such patches could be explained by impact ionization due to soft particle precipitation into PMAFs traces. In spite of the faint signature of the baby patches, two coherent HF radars of the SuperDARN network observed backscatter echoes in the central polar cap, which represented signatures of plasma irregularities associated with the baby patches. These indicate that patches created from PMAFs have the potential to affect the satellite communications environment in the central polar cap region.
Scientific journal, English - Edge of polar cap patches
K. Hosokawa; S. Taguchi; Y. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 121, 4, 3410-3420, Apr. 2016, Peer-reviwed, On the night of 4 December 2013, a sequence of polar cap patches was captured by an all-sky airglow imager (ASI) in Longyearbyen, Norway (78.1 degrees N, 15.5 degrees E). The 630.0 nm airglow images from the ASI of 4 second exposure time, oversampled the emission of natural lifetime (with quenching) of at least similar to 30 sec, introduce no observational blurring effects. By using such high-quality ASI images, we succeeded in visualizing an asymmetry in the gradients between the leading/ trailing edges of the patches in a 2-D fashion. The gradient in the leading edge was found to be 2-3 times steeper than that in the trailing edge. We also identified fingerlike structures, appearing only along the trailing edge of the patches, whose horizontal scale size ranged from 55 to 210 km. These fingers are considered to be manifestations of plasma structuring through the gradient-drift instability (GDI), which is known to occur only along the trailing edge of patches. That is, the current 2-D observations visualized, for the first time, how GDI stirs the patch plasma and such a mixing process makes the trailing edge more gradual. This result strongly implies a close connection between the GDI-driven plasma stirring and the asymmetry in the large-scale shape of patches and then suggests that the fingerlike structures can be used as markers to estimate the fine-scale structure in the plasma flow within patches.
Scientific journal, English - Lower thermospheric wind variations in auroral patches during the substorm recovery phase
Shin-ichiro Oyama; Kazuo Shiokawa; Yoshizumi Miyoshi; Keisuke Hosokawa; Brenton J. Watkins; Junichi Kurihara; Takuo T. Tsuda; Christopher T. Fallen
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 121, 4, 3564-3577, Apr. 2016, Peer-reviwed, Measurements of the lower thermospheric wind with a Fabry-Perot interferometer (FPI) at Tromso, Norway, found the largest wind variations in a night during the appearance of auroral patches at the substorm recovery phase. Taking into account magnetospheric substorm evolution of plasma energy accumulation and release, the largest wind amplitude at the recovery phase is a fascinating result. The results are the first detailed investigation of the magnetosphere-ionosphere-thermosphere coupled system at the substorm recovery phase using comprehensive data sets of solar wind, geomagnetic field, auroral pattern, and FPI-derived wind. This study used three events in November 2010 and January 2012, particularly focusing on the wind signatures associated with the auroral morphology, and found three specific features: (1) wind fluctuations that were isolated at the edge and/or inthe darker area of an auroral patchwith the largest vertical amplitude up to about 20m/s and with the longest oscillation period about 10min, (2) when the convection electric field was smaller than 15mV/m, and (3) wind fluctuations that were accompanied by pulsating aurora. This approach suggests that the energy dissipation to produce the wind fluctuations is localized in the auroral pattern. Effects of the altitudinal variation in the volume emission rate were investigated to evaluate the instrumental artifact due to vertical wind shear. The small electric field values suggest weak contributions of the Joule heating and Lorentz force processes in wind fluctuations. Other unknown mechanisms may play a principal role at the recovery phase.
Scientific journal, English - GPS scintillations in the high latitudes during periods of dayside and nightside reconnection
L. B. N. Clausen; J. I. Moen; K. Hosokawa; J. M. Holmes
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 121, 4, 3293-3309, Apr. 2016, Peer-reviwed, We use an automated procedure to identify periods of enhanced dayside reconnection followed by enhanced nightside reconnection in measurements of the polar cap size by the Active Magnetosphere and Planetary Electrodynamics Response Experiment between January 2010 and December 2012; we find 490 such events. We investigate the dynamics of the spatial distributions of the total electron content (TEC) and phase scintillations of Global Positioning System (GPS) signals across the northern polar region and here report three important findings: (1) While a TEC enhancement (due to polar cap patches) propagates across the polar cap during these events, this enhancement is not associated with significant GPS phase scintillations. (2) Instead, a significant impact on GPS signal quality is first found when the TEC enhancements cross the nightside auroral boundary. (3) In combination with upward field-aligned currents, these TEC enhancements cause the strongest GPS phase scintillations. We conclude that polar cap patches are not, as previously thought, a space weather threat inside the polar cap but instead reveal their biggest impact once they reach the nightside auroral oval, in particular when combined with upward field-aligned currents.
Scientific journal, English - Spatiotemporally resolved electrodynamic properties of a Sun-aligned arc over Resolute Bay
G. W. Perry; H. Dahlgren; M. J. Nicolls; M. Zettergren; J. -P. St-Maurice; J. L. Semeter; T. Sundberg; K. Hosokawa; K. Shiokawa; S. Chen
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 120, 11, 9977-9987, Nov. 2015, Peer-reviwed, Common volume measurements by the Resolute Bay Incoherent Scatter Radar-North (RISR-N) and Optical Mesosphere and Thermosphere Imagers (OMTI) have been used to clarify the electrodynamic structure of a Sun-aligned arc in the polar cap. The plasma parameters of the dusk-to-dawn drifting arc and surrounding ionosphere are extracted using the volumetric imaging capabilities of RISR-N. Multipoint line-of-sight RISR-N measurements of the plasma drift are inverted to construct a time sequence of the electric field and field-aligned current system of the arc. Evidence of dramatic electrodynamic and plasma structuring of the polar cap ionosphere due to the arc is described. One notable feature of the arc is a meridionally extended plasma density depletion on its leading edge, located partially within a downward field-aligned current region. The depletion is determined to be a by-product of enhanced chemical recombination operating on a time scale of 15 min. A similarly shaped electric field structure of over 100 mV/m and line-of-sight ion temperatures nearing 3000 K were collocated with the depletion.
Scientific journal, English - Three-dimensional imaging of the plasma parameters of a moving cusp aurora
Satoshi Taguchi; Keisuke Hosokawa; Yasunobu Ogawa
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 133, 98-110, Oct. 2015, Peer-reviwed, During a period of negative IMF B-Z on 13 January 2013, an all-sky imager at Longyearbyen, Svalbard observed a mesoscale aurora moving towards the east-northeast in the cusp, passing through the field of view of the EISCAT Svalbard Radar (ESR) elevation scan. The elevation scans that were being performed at that time have a horizontal coverage of approximately 300 km, at an altitude of 300 km. The plasma data obtained from the elevation scans and the 630-nm aurora emission data from the all-sky imager have shown that ion temperature enhanced 50-60 s earlier than electron density, and that the maximum auroral intensity in the ESR's field of view occurred about 40 s after the electron density enhancement. On the basis of these results we have constructed three-dimensional images of elevated ion temperatures and enhanced electron density associated with the mesoscale moving cusp aurora. The three-dimensional image shows that the enhancement of the ion temperature is prominent in the horizontal area of similar to 160 km x similar to 80 km below an altitude of similar to 300 km, and that this volume forms on the forward side of the enhanced electron density region. We interpret these configurations as being a result of a mesoscale twin-cell convection, which is embedded in the background flow such that the symmetrical axis of the twin-cell is inclined from the background flow direction by several tens of degrees. Our method for visualizing three-dimensional features such as these could be an effective approach to understanding the mesoscale dynamics of the cusp, which is usually located in latitudes that are difficult for the currently-operated radars that permit three-dimensional, simultaneous measurements to investigate. (C) 2015 Elsevier Ltd. All rights reserved.
Scientific journal, English - On the symmetry of ionospheric polar cap patch exits around magnetic midnight
J. Moen; K. Hosokawa; N. Gulbrandsen; L. B. N. Clausen
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 120, 9, 7785-7797, Sep. 2015, Peer-reviwed, In this paper we examine how polar cap patches, which have been frozen into the antisolar flow over the polar cap, are transported into the nighttime auroral oval. First we present a detailed case study from 12 January 2002, with continuous observations of polar cap patches exiting into the nighttime auroral oval in the Scandinavian sector. Satellite images of the auroral oval and all-sky camera observations of 630.0nm airglow patches are superimposed onto Super Dual Auroral Radar Network convection maps. These composite plots reveal that polar cap patches exit on both the dusk and on the dawn convection cells. Then we present statistics based on 8years of data from the meridian scanning photometer at Ny-Aalesund, Svalbard, to investigate the possible interplanetary magnetic field (IMF) B-y influence on the distribution of patch exits around magnetic midnight. The magnetic local time distribution of patch exits is almost symmetric around magnetic midnight, independent of IMF B-y polarity. Synthesizing these observations with previous results, we propose a three-step mechanism for why patch material exits symmetrically around midnight. First, intake of patch material occurs on both convection cells for both IMF B-y polarities. Second, plasma intake by transient magnetopause reconnection stretches the newly cut polar cap patches into dawn-dusk elongated forms during their transport into the polar cap. And finally at exit, dawn-dusk elongated patches are split and diverted toward both the dawn and dusk flanks when grabbed by transient tail reconnection.
Scientific journal, English - Multi-instrument, high-resolution imaging of polar cap patch transportation
E. G. Thomas; K. Hosokawa; J. Sakai; J. B. H. Baker; J. M. Ruohoniemi; S. Taguchi; K. Shiokawa; Y. Otsuka; A. J. Coster; J. -P. St.-Maurice; K. A. McWilliams
RADIO SCIENCE, AMER GEOPHYSICAL UNION, 50, 9, 904-915, Sep. 2015, Peer-reviwed, Transionospheric radio signals in the high-latitude polar cap are susceptible to degradation when encountering sharp electron density gradients associated with discrete plasma structures, or patches. Multi-instrument measurements of polar cap patches are examined during a geomagnetic storm interval on 22 January 2012. For the first time, we monitor the transportation of patches with high spatial and temporal resolution across the polar cap for 1-2 h using a combination of GPS total electron content (TEC), all-sky airglow imagers (ASIs), and Super Dual Auroral Radar Network (SuperDARN) HF radar backscatter. Simultaneous measurements from these data sets allow for continuous tracking of patch location, horizontal extent, and velocity despite adverse observational conditions for the primary technique (e.g., sunlit regions in the ASI data). Spatial collocation between patch-like features in relatively coarse but global GPS TEC measurements and those mapped by high-resolution ASI data was very good, indicating that GPS TEC can be applied to track patches continuously as they are transported across the polar cap. In contrast to previous observations of cigar-shaped patches formed under weakly disturbed conditions, the relatively narrow dawn-dusk extent of patches in the present interval (500-800 km) suggests association with a longitudinally confined plasma source region, such as storm-enhanced density (SED) plume. SuperDARN observations show that the backscatter power enhancements corresponded to the optical patches, and for the first time we demonstrate that the motion of the optical patches was consistent with background plasma convection velocities.
Scientific journal, English - Ionospheric variation during pulsating aurora
K. Hosokawa; Y. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 120, 7, 5943-5957, Jul. 2015, Peer-reviwed, We have statistically analyzed data from the European Incoherent Scatter (EISCAT) UHF/VHF radars in TromsO(69.60 degrees N, 19.20 degrees E), Norway, to reveal how the occurrence of pulsating auroras (PsAs) modifies the electron density profile in the ionosphere. By checking five winter seasons' (2007-2012) observations of all-sky aurora cameras of the National Institute of Polar Research in TromsO, we have extracted 21 cases of PsA. During these PsA events, either the UHF or VHF radar of EISCAT was operative and the electron density profiles were obtained along the field-aligned or vertical direction near the zenith. From these electron density measurements, we calculated h(m)E (E region peak height) and NmE (E region peak density), which are proxies for the energy and flux of the precipitating PsA electrons, respectively. Then, we examined how these two parameters changed during the evolution of 21 PsA events in a statistical fashion. The results can be summarized as follows: (1) h(m)E is lower (the energy of precipitation electrons is higher) during the periods of PsA than that in the surrounding interval; (2) when NmE is higher (flux of PsA electrons is larger), h(m)E tends to be lower (precipitation is harder); (3) h(m)E is lower and NmE is larger in the later magnetic local time; and (4) when the AE index during the preceding substorm is larger, h(m)E is lower and NmE is larger. These tendencies are discussed in terms of the characteristics of particles and plasma waves in the source of PsA in the magnetosphere. In addition to the statistics of the EISCAT data, we carried out several detailed case studies, in which the altitude profiles of the electron density were derived by separating the On and Off phases of PsA. This allows us to estimate the true altitude profiles of the PsA ionization, which can be used for estimating the characteristic energy of the PsA electrons and better understanding the wave-particle interaction process in the magnetosphere.
Scientific journal, English - Introduction to special section on pulsating aurora and related magnetospheric phenomena
Keisuke Hosokawa; Yoshizumi Miyoshi; Wen Li
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 120, 7, 5341-5343, Jul. 2015, Peer-reviwed, Pulsating aurora (PsA) is known as one of the major classes of aurora, which almost always appears during the recovery phase of substorm. Since 1960s, PsA has been extensively studied by using ground-based observations combined with rocket and satellite measurements. Still, however, the underlying processes creating auroral pulsations remain to be understood. Because of these, vast numbers of ground-based optical and radio instruments have been employed during the last decade to better observe the dynamic nature of PsA. In addition, there are several ongoing and planned ground-based and satellite collaborations aimed at understanding the electromagnetic coupling between magnetospheric processes (whistler mode chorus and ECH waves) and PsA seen on the ground. This special section focuses on observational (ground-based/satellites), theoretical, and modeling aspects of PsA and related phenomena in the magnetosphere.
Scientific journal, English - A thermospheric Na layer event observed up to 140km over Syowa Station (69.0 degrees S, 39.6 degrees E) in Antarctica
T. T. Tsuda; X. Chu; T. Nakamura; M. K. Ejiri; T. D. Kawahara; A. S. Yukimatu; K. Hosokawa
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 42, 10, 3647-3653, May 2015, Peer-reviwed, We report a thermospheric Na layer event (up to 140km) observed by lidar in the night of 23-24 September 2000 at Syowa (69.0 degrees S, 39.6 degrees E), Antarctica. The thermospheric Na number densities were 2-9cm(-3) at 110-140km, 3 orders of magnitude smaller than the peak density of the normal layer at 80-110km. The thermospheric Na layers exhibited a wave-like structure with a period of 1-2h. The colocated ionospheric/auroral observations showed sporadic E layers over Syowa through the night and an enhancement of the ionospheric/auroral activity around south side of Syowa at the event beginning. Adopting the theory by Chu et al. (2011), we hypothesize that the thermospheric Na layers are neutralized from converged Na+ layers. An envelope calculation shows good consistency with the observations.
Scientific journal, English - Investigating the particle precipitation of a moving cusp aurora using simultaneous observations from the ground and space
Satoshi Taguchi; Keisuke Hosokawa; Yasunobu Ogawa
PROGRESS IN EARTH AND PLANETARY SCIENCE, SPRINGER, 2, 11, May 2015, Peer-reviwed, Using observations of a moving cusp aurora from a high-sensitivity all-sky imager at Longyearbyen, Svalbard, and in situ observations of the precipitating particles from a spacecraft that flew over the aurora, we examined the particle precipitation features in the early and final stages of the moving cusp aurora. We focused on two auroral structures created near noon, separated by approximately 3 min, during a southwestward interplanetary magnetic field (IMF) condition on 17 December 2012. The second auroral structure occurred when the IMF turned further southward. Immediately after the appearance of the latter structure, the two auroral structures were adjacently situated, and the DMSP F18 spacecraft passed through these regions. A detailed comparison of the data from particle spectrometers onboard the spacecraft and the 630 nm aurora image data demonstrates that the ion precipitation in the young cusp aurora (i.e., second auroral structure) had a high energy flux, whereas that in the old cusp aurora (i.e., first auroral structure) had a very low energy flux. For the electron precipitation, the features in both regions were found to be very similar; the energy flux at approximately 100 eV often exceeded 1 x 10(9) eV cm(-2) s(-1) sr(-1) eV(-1) in both regions. This indicates that the electron precipitation in the moving cusp aurora is maintained at a high flux level over a certain interval from its starting time. Thus, we suggest that the electron precipitation flux in the moving cusp aurora is controlled by a mechanism independent of the ion precipitation.
Scientific journal, English - CDF data archive and integrated data analysis platform for ERG-related ground data developed by ERG Science Center (ERG-SC)
Hori, T; Y. Miyashita; Y. Miyoshi; K. Seki; T. Segawa; Y.-M. Tanaka; K. Keika; M. Shoji; I. Shinohara; K. Shiokawa; Y. Otsuka; S. Abe; A. Yoshikawa; K. Yumoto; Y. Obana; N. Nishitani; A. S. Yukimatu; T. Nagatsuma; M. Kunitake; K. Hosokawa; Y. Ogawa; K. T. Murata; M. Nose; H. Kawano; T. Sakanoi
J. Space Sci. Info. Jpn, Japan Aerospace Exploration Agency, 4, 75-89, 2015, Peer-reviwed
Scientific journal, English - Direct observations of blob deformation during a substorm
T. Ishida; Y. Ogawa; A. Kadokura; K. Hosokawa; Y. Otsuka
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 33, 5, 525-530, 2015, Peer-reviwed, Ionospheric blobs are localized plasma density enhancements, which are mainly produced by the transportation process of plasma. To understand the deformation process of a blob, observations of plasma parameters with good spatial-temporal resolution are desirable. Thus, we conducted the European Incoherent Scatter radar observations with high-speed meridional scans (60-80 s) during October and December 2013, and observed the temporal evolution of a blob during a substorm on 4 December 2013. This paper is the first report of direct observations of blob deformation during a substorm. The blob deformation arose from an enhanced plasma flow shear during the substorm expansion phase, and then the blob split into two smaller-scale blobs, whose scale sizes were more than similar to 100 km in latitude. Our analysis indicates that the Kelvin-Helmholtz instability and dissociative recombination could have deformed the blob structure.
Scientific journal, English - Interhemispheric auroral symmetry and asymmetry from ground-based conjugate observations
Sato, N; A. Kadokura; T. Motoba; K. Hosokawa; G. Bjornsson; Th. Saemundsson
Auroral Dynamics and Space Weather, Geophysical Monograph 215, Edited by Yongliang Zhang and Larry J. Paxton, American Geophysical Union, doi:10.1002/9781118978719.ch11-161, 2015, Peer-reviwed
Scientific journal, English - Observations of GPS scintillation during an isolated auroral substorm
Keisuke Hosokawa; Yuichi Otsuka; Yasunobu Ogawa; Takuya Tsugawa
Progress in Earth and Planetary Science, Springer Berlin Heidelberg, 1, 1, 01 Dec. 2014, Peer-reviwed, Invited, This paper reports simultaneous observations of ionospheric scintillation during an auroral substorm that were made using an all-sky full-color digital single-lens reflex (DSLR) camera (ASC) and a Global Positioning System (GPS) ionospheric scintillation and total electron content monitor (GISTM) in Tromsø (69.60 N, 19.20 E), Norway. On the night of November 19, 2009, a small substorm occurred in northern Scandinavia. The ASC captured its temporal evolution from the beginning of the growth phase to the end of the recovery phase. The amplitude scintillation, as monitored by the S4 index from the GISTM, did not increase in any substorm phase. By contrast, phase scintillation, as measured by the σφ index, occurred when discrete auroral arcs appeared on the GPS signal path. In particular, the phase scintillation was significantly enhanced for a few minutes immediately after the onset of the expansion phase. During this period, bright and discrete auroral forms covered the entire sky, which implies that structured precipitation on the scale of a few kilometers to a few tens of kilometers dominated the electron density distribution in the E region. Such inhomogeneous ionization structures probably produced significant changes in the refractive index and eventually resulted in the enhancement of the phase scintillation.
Scientific journal, English - 3D imaging reveals electrodynamics of polar cap aurora
Hanna Dahlgren; Gareth Perry; Jean-Pierre St Maurice; Torbjorn Sundberg; Keisuke Hosokawa; Joshua L. Semeter; Michael J. Nicolls; Kazuo Shiokawa
ASTRONOMY & GEOPHYSICS, OXFORD UNIV PRESS, 55, 5, Oct. 2014, Peer-reviwed
Scientific journal, English - 3D imaging reveals electrodynamics of polar cap aurora
Hanna Dahlgren; Gareth Perry; Jean-Pierre St Maurice; Torbjorn Sundberg; Keisuke Hosokawa; Joshua L. Semeter; Michael J. Nicolls; Kazuo Shiokawa
ASTRONOMY & GEOPHYSICS, OXFORD UNIV PRESS, 55, 5, Oct. 2014, Peer-reviwed, Invited
Scientific journal, English - Storm time enhancements of 630.0 nm airglow associated with polar cap patches
J. Sakai; K. Hosokawa; S. Taguchi; Y. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 119, 3, 2214-2228, Mar. 2014, Peer-reviwed, We examined the brightness of 630.0 nm airglow, I-630, associated with polar cap patches observed during a magnetic storm that occurred on 22 January 2012. Brightness was measured using an all-sky imager (ASI) located at Longyearbyen, Svalbard. The observed I-630 was compared with the F region electron density observed by the European Incoherent Scatter Svalbard Radar (ESR). The I-630 was positively correlated with the F-2 layer peak electron density, NmF(2), and inversely correlated with the altitude of the F2 layer peak electron density, hmF(2), as expected from the known relationship between these parameters. To estimate the altitude of the peak emission of the airglow, we performed model calculations of the volume emission rate, V-630, under quiet and disturbed conditions, using Mass Spectrometer Incoherent Scatter modeled neutral gas profiles and the electron density profile obtained from the ESR data. In order to validate the V-630 calculation, I-630 was calculated by integrating the V-630 along altitude and then compared with the ASI-observed I-630. During the observation periods the measured brightness frequently exceeded the calculated I-630; we infer that in most cases, low-energy particle precipitation is responsible for the extra brightness. However, when there was less particle precipitation, the observed values were in good agreement with the calculated values. Under the magnetically disturbed conditions during our observations, the model calculation showed that the altitude of V-630 peak increases, the thickness of the emission layer increases, and patch brightness increases.
Scientific journal, English - Storm time enhancements of 630.0 nm airglow associated with polar cap patches
J. Sakai; K. Hosokawa; S. Taguchi; Y. Ogawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 119, 3, 2214-2228, 2014, Peer-reviwed, We examined the brightness of 630.0 nm airglow, I630, associated with polar cap patches observed during a magnetic storm that occurred on 22 January 2012. Brightness was measured using an all-sky imager (ASI) located at Longyearbyen, Svalbard. The observed I630 was compared with the F region electron density observed by the European Incoherent Scatter Svalbard Radar (ESR). The I630 was positively correlated with the F 2 layer peak electron density, NmF2, and inversely correlated with the altitude of the F2layer peak electron density, hmF2, as expected from the known relationship between these parameters. To estimate the altitude of the peak emission of the airglow, we performed model calculations of the volume emission rate, V630, under quiet and disturbed conditions, using Mass Spectrometer Incoherent Scatter modeled neutral gas profiles and the electron density profile obtained from the ESR data. In order to validate the V630 calculation, I630 was calculated by integrating the V630 along altitude and then compared with the ASI-observed I630. During the observation periods the measured brightness frequently exceeded the calculated I630
we infer that in most cases, low-energy particle precipitation is responsible for the extra brightness. However, when there was less particle precipitation, the observed values were in good agreement with the calculated values. Under the magnetically disturbed conditions during our observations, the model calculation showed that the altitude of V630 peak increases, the thickness of the emission layer increases, and patch brightness increases. Key Points Optical intensity of polar cap patch under disturbed conditions is examined Polar patch 630 nm airglow enhances under disturbed conditions Altitude and thickness of emission layer increase under disturbed conditions ©2014. American Geophysical Union. All Rights Reserved.
Scientific journal, English - Global imaging of polar cap patches with dual airglow imagers
K. Hosokawa; S. Taguchi; K. Shiokawa; Y. Otsuka; Y. Ogawa; M. Nicolls
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 41, 1, 1-6, Jan. 2014, Peer-reviwed, During a 2 h interval from 2240 to 2440 UT on 12 November 2012, regions of increased 630.0 nm airglow emissions were simultaneously detected by dual all-sky imagers in the polar cap, one at Longyearbyen, Norway (78.1 degrees N, 15.5 degrees E) and the other at Resolute Bay, Canada (74.7 degrees N, 265.1 degrees E). The Resolute Bay incoherent scatter radar observed clear enhancements of the F region electron density up to 10(12) m(-3) within these airglow structures which indicates that these are optical manifestations of polar cap patches propagating across the polar cap. During this interval of simultaneous airglow imaging, the nightside/dawnside (dayside/duskside) half of the patches was captured by the imager at Longyearbyen (Resolute Bay). This unique situation enabled us to estimate the dawn-dusk extent of the patches to be around 1500 km, which was at least 60-70% of the width of the antisunward plasma stream seen in the Super Dual Auroral Radar Network convection maps. In contrast to the large extent in the dawn-dusk direction, the noon-midnight thickness of each patch was less than 500 km. These observations demonstrate that there exists a class of patches showing cigar-shaped structures. Such patches could be produced in a wide range of local time on the dayside nearly simultaneously and spread across many hours of local time soon after their generation.
Scientific journal, English - Simultaneous NLC and PMSE Observations at Syowa, Antarctica
Hosokawa, K; Y. Takeda; A. Kadokura; A. S. Yukimatu; N. Sato
Antarctic Record, National Institute of Polar Research, 57, 317-328, 2014, Peer-reviwed
Research institution, English - Planetary wave oscillations observed in ozone and PMSE data from Antarctica
T. D. Demissie; K. Hosokawa; N. H. Kleinknecht; P. J. Espy; R. E. Hibbins
Journal of Atmospheric and Solar-Terrestrial Physics, 105-106, 105-106, 207-213, Dec. 2013, Peer-reviwed, The effect of temperature variations caused by planetary waves on the occurrence of Polar Mesospheric Summer Echoes (PMSE) has been a subject of recent research. These same temperature fluctuations have also been shown to modulate the ozone volume mixing ratio above 30. km. In this study, ground-based radiometer measurements of ozone mixing ratio profiles at Troll station (72°S, 2°E), Antarctica are compared with PMSE extracted from the near-range measurements of the Sanae (72°S, 2°W) Super Dual Auroral Radar (SuperDARN) over the radiometer field of view. We show here that the resulting quasi-periodic fluctuations in PMSE correlate with the variations seen in the ozone. The ozone mixing-ratio variations may then be used to trace the phase variation of planetary waves with height to demonstrate that they extend from the stratosphere up to the mesopause. The results indicate that the modulation of PMSE occurrence frequency during the summer of 2009/10 is the result of two planetary waves with similar zonal structure and period, but with different vertical phase structures. © 2013.
Scientific journal, English - The interconnection between cross-polar cap convection and the luminosity of polar cap patches
G. W. Perry; J. -P. St-Maurice; K. Hosokawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 118, 11, 7306-7315, Nov. 2013, Peer-reviwed, The transport of patches of ionization across the polar cap is carried by the convection electric field, which imposes an ExB drift to the plasma. This drift has an upward component when the plasma is convected toward the north magnetic pole and a downward component as it moves away from the pole. The vertical motion modulates the rate at which recombination operates, which in turn is directly related to the luminosity of the patches. We show here that if a rapid increase in the electric field produces a downward velocity in excess of 10 m/s, the luminosity of the patches will at first increase before undergoing a marked decrease, in association with an increase in the recombination rates. Both the change in luminosity and the time scale for the temporary increase primarily depend on the vertical velocity, that is, on the strength of the convection electric field and on the magnetic latitude. Increases in luminosity by up to a factor of 2 or more are possible. The time scales for the variations are of the order of 10 to 20 min. We present an example of an actual luminosity modulation obtained over Resolute Bay, Canada, that agrees well with the proposed theory.
Scientific journal, English - Relationship between auroral substorm and ion upflow in the nightside polar ionosphere
Y. Ogawa; M. Sawatsubashi; S. C. Buchert; K. Hosokawa; S. Taguchi; S. Nozawa; S. Oyama; T. T. Tsuda; R. Fujii
Journal of Geophysical Research: Space Physics, 118, 11, 7426-7437, Nov. 2013, Peer-reviwed, We investigated ionospheric ion upflow during an auroral substorm using simultaneous European Incoherent Scatter radar and IMAGE satellite data. Approximately 6 min after an initial brightening identified with data from the IMAGE wideband imaging camera instrument, ion upflow was seen and the electron temperature became enhanced, too. The ion upflow, with a velocity of about 150 m/s, and the electron temperature enhancement lasted for about 25 min. During the poleward expansion phase, surges of large upward ion velocity and flux, and high ion and electron temperatures occurred over Longyearbyen. The upward ion flux reached 2 × 1014 m-2s-1. Naturally enhanced ion-acoustic lines (NEIALs) were seen near the poleward edge of the expanded auroral oval both near the end of expansion phase 17 min after onset and also later in the recovery phase. The NEIALs seemed to be accompanied by another type of enhanced echoes, obliquely to the local geomagnetic field. Data from the Low Energy Neutral Atom instrument on the IMAGE satellite show that energetic neutral oxygen reaches the IMAGE satellite about 40 min after the initial brightening, and oxygen continues to get detected during the recovery phase. We propose that ion upflow at the poleward edge of the auroral oval during the expansion phase is related to ion/neutral outflow with energy below 18-27 eV, whereas during the recovery phase of a substorm upward ions are accelerated up to about 60 eV and flow out in the entire polar region. Key Points Ion upflow was identified approximately 6 min after an initial brightening Surges of large upward ion velocity occurred during poleward expansion phase Energetic neutral oxygen was observed 40 min after the initial brightening ©2013. American Geophysical Union. All Rights Reserved.
Scientific journal, English - First observations of polar mesosphere summer echoes by SuperDARN Zhongshan radar
E. X. Liu; H. Q. Hu; K. Hosokawa; R. Y. Liu; Z. S. Wu; Z. Y. Xing
Journal of Atmospheric and Solar-Terrestrial Physics, 104, 104, 39-44, Nov. 2013, Peer-reviwed, We report the first observations of PMSE by SuperDARN Zhongshan radar in Antarctica and present a statistical analysis of PMSE from 2010 to 2012. The seasonal variations of occurrence are consistent with those before, with an obvious enhancement at the beginning of summer and a maximum several days after summer solstice. The special features of diurnal variations were observed because of high geomagnetic latitude of Zhongshan Station, which is that the maximum is near local midnight and the secondary maximum appears 1-2. h after the local noon. The results proved that the auroral particle precipitation plays a fairly important role in the PMSE occurrence. © 2013.
Scientific journal, English - Large flow shears around auroral beads at substorm onset
K. Hosokawa; S. E. Milan; M. Lester; A. Kadokura; N. Sato; G. Bjornsson
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 40, 19, 4987-4991, Oct. 2013, Peer-reviwed, We present a fine-scale electrodynamic structure behind the auroral beads observed immediately before substorm onset, as inferred from high spatial and temporal resolution measurements of substorm with an all-sky TV camera (ATV) and a coherent high frequency radar of Super Dual Auroral Radar Network in Iceland. On the night of 24 September 2006, the ATV observed eastward propagating auroral beads in the initial brightening arc of a substorm just prior to the poleward expansion. During the sequential passage of the beads across the radar beams, the radar detected large velocity flow shears whose magnitude was in excess of 0.27 s(-1). The observations suggest that flow shears were located very close to the center of the beads; thus, they corresponded to electric fields converging toward the beads, which is consistent with the existence of upward field-aligned currents (FACs) flowing out of the beads. The temporal and spatial resolutions of the current radar measurement were still insufficient for fully resolving the detailed electrodynamic structure behind the fast moving auroral beads. At least, however, we can suggest the existence of highly localized filamentary FAC structures behind the beads, which would be an important consequence of possible plasma instabilities operating in the M-I coupling region or near the equatorial plane of the magnetosphere.
Scientific journal, English - Characteristics of medium-scale traveling ionospheric disturbances observed near the Antarctic Peninsula by HF radar
A. Grocott; K. Hosokawa; T. Ishida; M. Lester; S. E. Milan; M. P. Freeman; N. Sato; A. S. Yukimatu
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 118, 9, 5830-5841, Sep. 2013, Peer-reviwed, We present a survey of medium-scale traveling ionospheric disturbances (MSTIDs) observed by a Super Dual Auroral Radar Network HF radar located in the Falkland Islands between May 2010 and April 2011. The radar has a field of view that overlooks the Antarctic Peninsula, a known hot spot of gravity wave activity. We present observations of radar ground-backscatter data, in which the signatures of MSTIDs are manifested as structured enhancements in echo power. Observed periods were in the range 30-80min, corresponding to frequencies of 0.2-0.6mHz. Wavelengths were generally in the range 200-800km and phase speeds in the range 100-300ms(-1). These values are within the ranges typically associated with medium-scale gravity waves. We find a primary population of northward (equatorward) propagating MSTIDs, which demonstrate an association with enhanced solar wind-magnetosphere coupling and a smaller, westward propagating population, that could be associated with atmospheric gravity waves excited by winds over the Andean and Antarctic Peninsula mountains or by the high winds of the Antarctic Polar Vortex.
Scientific journal, English - Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm
J. Sakai; S. Taguchi; K. Hosokawa; Y. Ogawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 118, 1, 462-471, 2013, Peer-reviwed, A series of steep plasma depletions was observed in the dayside polar cap during an interval of highly enhanced electron density on 14 October 2000 through EISCAT Svalbard Radar (ESR) field-aligned measurements and northward-directed low-elevation measurements. Each depletion started with a steep dropoff to as low as 1011 m- 3 from the enhanced level of ∼3 × 1012 m-3 at F2 region altitudes, and it continued for 10-15 min before returning to the enhanced level. These depletions moved poleward at a speed consistent with the observed ion drift velocity. DMSP spacecraft observations over an extended period of time which includes the interval of these events indicate that a region of high ion densities extended into the polar cap from the equatorward side of the cusp, i.e., a tongue of ionization existed, and that the ion densities were very low on its prenoon side. Solar wind observations show that a sharp change from IMF By >
0 to By <
0 is associated with each appearance of the ESR electron density dropoff. From this unprecedented clear correlation we present a specific scenario: the series of plasma density depletions observed using the ESR is a result of the poleward drift of the undulating boundary of the tongue of ionization
this undulation is created in the cusp roughly 20 min before the ESR observation by the azimuthal intrusion, in response to the rapid prenoon shift of the footprint of the reconnection line, of the low-density plasmas originating in the morning sector. © 2012. American Geophysical Union. All Rights Reserved.
Scientific journal, English - Periodicities of polar cap patches
K. Hosokawa; S. Taguchi; Y. Ogawa; T. Aoki
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 118, 1, 447-453, 2013, Peer-reviwed, A highly sensitive all-sky electron multiplier charge-coupled device airglow imager has been operative in Longyearbyen, Norway since October 2011. The imager captures 630.0 nm all-sky images with an exposure time of 4 s, which is about 10 times shorter than that achieved by conventional cooled CCD imagers. This allows us to visualize the structure of polar cap patches without blurring effects and better estimate their periodicities. We present, as one of the first results from the imager, an event of successive appearance of patches on the night of 21 December 2011. A time series of the optical intensity at zenith showed modulations having two distinguished periods, one at 40 min and the other at 5-12 min. One possible explanation is that such a coexistence of two different periodicities is a manifestation of simultaneous occurrence of patch generation processes on the 40 min periodicity was created by large-scale reconfiguration of the dayside convection pattern while the 5-12 min modulations were closely associated with mechanisms driven by pulsed reconnection on the dayside magnetopause. Such a combined effect of multiple patch generation processes may play a role in structuring patches
thus, it would be of particular importance for evaluating the space weather effects in the trans-ionospheric communications environment in the polar cap. © 2012. American Geophysical Union. All Rights Reserved.
Scientific journal, English - トロムソ/ロングイアビンにおけるオーロラ観測用並列イメージャーの大量データ処理と可視化
小川泰信; 門倉昭; 元場哲郞; 田中良昌; 細川敬祐
宇宙科学情報解析論文誌, 2, 51-61, 2013, Peer-reviwed - Processing and visualization of large amounts of auroral data obtained with All-sky/Narrow field-of-view parallel imagers in Tromso and Longyearbyen
Ogawa, Y; A. Kadokura; T. Motoba; Y. Tanaka; K. Hosokawa
Journal of Space Science Informatics Japan, 2, 51-61, 2013, Peer-reviwed - An integrated analysis platform merging SuperDARN data within the THEMIS tool developed by ERG-Science Center (ERG-SC)
Hori T; N. Nishitani; Y. Miyoshi; Y. Miyashita; K. Seki; T. Segawa; K. Hosokawa; A. S. Yukimatu; Y. Tanaka; N. Sato; M. Kunitake; T. Nagatsuma
Adv. Polar. Sci., 24, doi:10.3724/SP.J.1085.2013.000, 2013, Peer-reviwed
Scientific journal, English - Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm
J. Sakai; S. Taguchi; K. Hosokawa; Y. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 118, 1, 462-471, Jan. 2013, Peer-reviwed, A series of steep plasma depletions was observed in the dayside polar cap during an interval of highly enhanced electron density on 14 October 2000 through EISCAT Svalbard Radar (ESR) field-aligned measurements and northward-directed low-elevation measurements. Each depletion started with a steep dropoff to as low as 10(11) m(-3) from the enhanced level of similar to 3 x 10(12) m(-3) at F2 region altitudes, and it continued for 10-15 min before returning to the enhanced level. These depletions moved poleward at a speed consistent with the observed ion drift velocity. DMSP spacecraft observations over an extended period of time which includes the interval of these events indicate that a region of high ion densities extended into the polar cap from the equatorward side of the cusp, i.e., a tongue of ionization existed, and that the ion densities were very low on its prenoon side. Solar wind observations show that a sharp change from IMF B-y > 0 to B-y < 0 is associated with each appearance of the ESR electron density dropoff. From this unprecedented clear correlation we present a specific scenario: the series of plasma density depletions observed using the ESR is a result of the poleward drift of the undulating boundary of the tongue of ionization; this undulation is created in the cusp roughly 20 min before the ESR observation by the azimuthal intrusion, in response to the rapid prenoon shift of the footprint of the reconnection line, of the low-density plasmas originating in the morning sector. Citation: Sakai, J., S. Taguchi, K. Hosokawa, and Y. Ogawa (2013), Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm, J. Geophys. Res. Space Physics, 118, 462-471, doi:10.1029/2012JA018138.
Scientific journal, English - Periodicities of polar cap patches
K. Hosokawa; S. Taguchi; Y. Ogawa; T. Aoki
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 118, 1, 447-453, Jan. 2013, Peer-reviwed, A highly sensitive all-sky electron multiplier charge-coupled device airglow imager has been operative in Longyearbyen, Norway since October 2011. The imager captures 630.0 nm all-sky imageswith an exposure time of 4 s, which is about 10 times shorter than that achieved by conventional cooled CCD imagers. This allows us to visualize the structure of polar cap patches without blurring effects and better estimate their periodicities. We present, as one of the first results from the imager, an event of successive appearance of patches on the night of 21 December 2011. A time series of the optical intensity at zenith showed modulations having two distinguished periods, one at 40 min and the other at 5-12 min. One possible explanation is that such a coexistence of two different periodicities is a manifestation of simultaneous occurrence of patch generation processes on the 40 min periodicity was created by large-scale reconfiguration of the dayside convection pattern while the 5-12 min modulations were closely associated with mechanisms driven by pulsed reconnection on the dayside magnetopause. Such a combined effect of multiple patch generation processes may play a role in structuring patches; thus, it would be of particular importance for evaluating the space weather effects in the trans-ionospheric communications environment in the polar cap. Citation: Hosokawa K., Taguchi S., Ogawa Y., Aoki T., (2012), Periodicities of polar cap patches, J. Geophys. Res. Space Physics, 118, 447-453, doi:10.1029/2012JA018165.
Scientific journal, English - Two-dimensional direct imaging of structuring of polar cap patches
K. Hosokawa; S. Taguchi; Y. Ogawa; J. Sakai
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 118, 10, 6536-6543, 2013, Peer-reviwed, A highly sensitive all-sky electron multiplier charge-coupled device airglow imager has been operative in Longyearbyen, Norway (78.1°N, 15.5°E), since October 2011. The imager obtains the 630.0 nm all-sky images with an exposure time of 4 s, which is about 10 times shorter than the conventional cooled CCD airglow imagers. This new equipment allows us to image the ongoing structuring of polar cap patches in 2-D fashion. Here we report a case in which faint undulations appeared along the trailing edge of patches propagating in the central polar cap. The separation between the fingers in the undulations was about 50-100 km and the e-folding time of their growth was ∼5 min. We suggest that the gradient-drift instability (GDI) is one of the possible generation mechanisms of the undulating structures. The reasons for this interpretation are (1) the asymmetry in the preference of structuring between the leading and trailing edges is qualitatively consistent with the GDI mechanism and (2) the linear growth rate of GDI calculated by using electron density estimates from simultaneous European Incoherent Scatter Svalbard radar observations is roughly consistent with the observed growth time of the fingers. Such "unstable polar cap patches" could be important sources of seed irregularities, which would eventually be broken down to smaller-scale density perturbations affecting the transionospheric satellite communications in the central polar cap. Key Points Visualize on-going structuring of polar cap patches in 2D fashion Faint undulations of the trailing edge of the patches were identified Structuring of patches can be explained by the gradient-drift instability ©2013. American Geophysical Union. All Rights Reserved.
Scientific journal, English - Double bursts inside a poleward-moving auroral form in the cusp
S. Taguchi; K. Hosokawa; Y. Ogawa; T. Aoki; M. Taguchi
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, doi:10.1029/2012JA018150, Dec. 2012, Peer-reviwed, Poleward-moving auroral forms (PMAF), the ionospheric signatures of flux transfer events (FTEs), are intermittent phenomena observed in the cusp during negative interplanetary magnetic field intervals. Previous meridian scanning photometer-based observations showed that the distribution of the separation time between successive PMAFs is maximum at similar to 3.5 min. In this paper we present initial results from a new high-sensitivity all-sky imager, which was set up at Longyearbyen, Svalbard, Norway in October 2011. The 630.0-nm all-sky images taken with a time resolution of 4 s reveal that one of the PMAFs that occurred with such typical separation times on 29 December 2011 comprises two consecutive auroral bursts-the first occurring in the PMAF immediately after it was seen and the second, similar to 2 min later, following almost the same route. This observation provides evidence that one PMAF could reflect double FTEs-there is not always a one-to-one correspondence between FTEs and PMAFs. Reconnection on the dayside magnetopause would be modulated with a period of similar to 2 min during the course of transient reconnection. Citation: Taguchi, S., K. Hosokawa, Y. Ogawa, T. Aoki, and M. Taguchi (2012), Double bursts inside a poleward-moving auroral form in the cusp, J. Geophys. Res., 117, A12301, doi:10.1029/2012JA018150.
Scientific journal, English - Space-time variability of polar cap patches: Direct evidence for internal plasma structuring
H. Dahlgren; G. W. Perry; J. L. Semeter; J. -P. St-Maurice; K. Hosokawa; M. J. Nicolls; M. Greffen; K. Shiokawa; C. Heinselman
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, doi:10.1029/2012JA017961, Sep. 2012, Peer-reviwed, Coordinated observations of ionospheric variability near the geomagnetic pole using the Resolute Bay Incoherent Scatter Radar (RISR-N), Super Dual Auroral Radar Network (SuperDARN) High Frequency (HF) radars, and all-sky imagers have clarified the relative contribution of structuring mechanisms operating on polar plasma patches. From the multipoint RISR-N observations, a three dimensional image can be constructed of the plasma parameters. The colocated coherent echoes from the SuperDARN radars provide information on field aligned irregularities, and from all-sky imagers located in Resolute Bay, Canada and Qaanaaq, Greenland, information is obtained on the emission brightness at different wavelengths. A good correlation is found between the location of the coherent, incoherent and optical signals of patches. From the SuperDARN radar data it is evident that plasma irregularities seem to be present throughout the region of enhanced electron density. The patches are observed to be formed in the cusp region due to bursty flux transfer events and are then transported across the polar cap. During the time period of about 10 minutes when a patch drifted through the RISR-N field of view, the patch seemed to undergo significant deformation in all three spatial dimensions, with density fluctuations of about 10% and spatial variations leading to stretching and tilting of the patch. The findings show that plasma structuring can likely occur within polar cap patches, which support previous suggestions that a patch is highly variable as it drifts across the polar cap, with a faster spread of irregularities throughout the patch as a result.
Scientific journal, English - Simultaneous ground-satellite observations of meso-scale auroral arc undulations
T. Motoba; K. Hosokawa; Y. Ogawa; N. Sato; A. Kadokura; S. E. Milan; M. Lester
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, doi:10.1029/2011JA017291, Jun. 2012, Peer-reviwed, We present simultaneous ground-based and in situ measurements of a train of meso-scale (about 100-300 km) auroral arc undulations, occurring in the postmidnight sector (similar to 1 MLT) between 0040 UT and 0054 UT on September 21, 2009. The undulations appeared at the auroral poleward boundary, and then moved eastward with a speed of 0.9-2.2 km s(-1). Dynamic behaviors of the associated meso-scale ionospheric plasma flows and current systems were also detected with the ground-based magnetometer and radar measurements within the all-sky camera field-of-view. During the interval of interest, simultaneous Cluster observations in the central near tail region (11-14 R-E down tail) were available, and especially the ionospheric footprint of Cluster 2 (CL2) was close to the optical auroral forms. CL2 observed strong fluctuations in the in situ magnetic field with amplitude of 5-10 nT whenever a bright arc area, and its trailing adjacent area, of the auroral undulations passed its ionospheric footprint. Such in situ magnetic field changes at CL2 could be considered as a manifestation of localized upward and downward field-aligned current sheets moving eastward at the central near-Earth tail boundary, linked to the meso-scale auroral undulation structures.
Scientific journal, English - GPS total electron content variations associated with poleward moving Sun-aligned arcs
P. T. Jayachandran; K. Hosokawa; K. Shiokawa; Y. Otsuka; C. Watson; S. C. Mushini; J. W. MacDougall; P. Prikryl; R. Chadwick; T. D. Kelly
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, doi:10.1029/2011JA017423, May 2012, Peer-reviwed, GPS total electron content (TEC) has shown quasiperiodic oscillations of varying amplitude associated with poleward moving Sun-aligned arcs. The amplitude of TEC variations showed a maximum of similar to 3 TECU and seemed to decrease as the arcs moved poleward from the source/generation region. Simultaneous DMSP data showed that fluctuations in TEC and optical intensification were caused by precipitation of high-energy (>500 eV) particles. Concurrent ionosonde observations also exhibited quasiperiodic variations (within limit of the resolution of the data) in peak ionospheric electron density of the ionosphere. Bottom height of the ionospheric layers produced by precipitating particles varied between 130 km (upper E region) and 300 km (F region), indicating variable particle precipitation energy. Frequency analysis of high-resolution TEC data showed a broad range of discrete frequency components from 1.60 mHz to 22.80 mHz present in the TEC oscillations, which may provide insight into the energization/modulation of precipitating particles by these oscillations. A broad distribution of equivalent vertical thickness of arcs was calculated using GPS TEC and ionosonde measurements of peak electron density. This distribution showed a minimum thickness of 21 km, a maximum of 84 km, and an average of 49 km. The equivalent vertical thickness also showed a linear relationship with bottomside height of the ionospheric layer (auroral arc). The relationship showed an increase in the vertical thickness with an increase in bottomside height of the layer. This relationship is a consequence of variations in the energy of the precipitating particles causing different ionospheric production profiles.
Scientific journal, English - Magnetic conjugacy of northern and southern auroral beads
Tetsuo Motoba; Keisuke Hosokawa; Akira Kadokura; Natsuo Sato
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 39, doi:10.1029/2012GL051599, Apr. 2012, Peer-reviwed, Auroral beads, i.e., azimuthally arrayed bright spots resembling a pearl necklace, have recently drawn attention as a possible precursor of auroral substorms. We used simultaneous, ground-based, all-sky camera observations from a geomagnetically conjugate Iceland-Syowa Station pair to demonstrate that the auroral beads, whose wavelength is similar to 30-50 km, evolve synchronously in the northern and southern hemispheres and have remarkable interhemispheric similarities. In both hemispheres: 1) they appeared almost at the same time; 2) their longitudinal wave number was similar similar to 300-400, corresponding bead separation being similar to 1 degrees in longitude; 3) they started developing into a larger scale spiral form at the same time; 4) their propagation speeds and their temporal evolution were almost identical. These interhemispheric similarities provide strong evidence that there is a common driver in the magnetotail equatorial region that controls the major temporal evolution of the auroral beads; thus, the magnetosphere plays a primary role in structuring the initial brightening arc in this scale size. Citation: Motoba, T., K. Hosokawa, A. Kadokura, and N. Sato (2012), Magnetic conjugacy of northern and southern auroral beads, Geophys. Res. Lett., 39, L08108, doi:10.1029/2012GL051599.
Scientific journal, English - Direct three-dimensional imaging of polar ionospheric structures with the Resolute Bay Incoherent Scatter Radar
H. Dahlgren; J. L. Semeter; K. Hosokawa; M. J. Nicolls; T. W. Butler; M. G. Johnsen; K. Shiokawa; C. Heinselman
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 39, doi:10.1029/2012GL050895., Mar. 2012, Peer-reviwed, Ionospheric plasma density structures in the dayside F-region of the polar cap are commonly occurring events, but adequate measurements of their formation and evolution have been sparse. With the advent of the advanced modular incoherent scatter radar RISR-N (Resolute Bay Incoherent Scatter Radar) it is now possible for the first time to study the temporal evolution of the plasma properties in the polar cap region in three dimensions, with a spatial resolution of tens of kilometers, from which the plasma rest frame can be experimentally established. We demonstrate the strength of the diagnostic with observations from an event of enhanced plasma density observed over Resolute Bay in December 2009. A colocated all-sky imager showed faint 630.0 and 557.7 nm emission corresponding to the plasma enhancements, and the structures could be traced back to a formation region in the open/closed field line boundary. This new plasma imaging technique will provide important information on the mechanisms controlling the structuring in the high latitude ionosphere. Citation: Dahlgren, H., J. L. Semeter, K. Hosokawa, M. J. Nicolls, T. W. Butler, M. G. Johnsen, K. Shiokawa, and C. Heinselman (2012), Direct three-dimensional imaging of polar ionospheric structures with the Resolute Bay Incoherent Scatter Radar, Geophys. Res. Lett., 39, L05104, doi:10.1029/2012GL050895.
Scientific journal, English - Double bursts inside a poleward-moving auroral form in the cusp
S. Taguchi; K. Hosokawa; Y. Ogawa; T. Aoki; M. Taguchi
Journal of Geophysical Research: Space Physics, 117, 12, 2012, Peer-reviwed, Poleward-moving auroral forms (PMAF), the ionospheric signatures of flux transfer events (FTEs), are intermittent phenomena observed in the cusp during negative interplanetary magnetic field intervals. Previous meridian scanning photometer-based observations showed that the distribution of the separation time between successive PMAFs is maximum at ∼3.5 min. In this paper we present initial results from a new high-sensitivity all-sky imager, which was set up at Longyearbyen, Svalbard, Norway in October 2011. The 630.0-nm all-sky images taken with a time resolution of 4 s reveal that one of the PMAFs that occurred with such typical separation times on 29 December 2011 comprises two consecutive auroral bursts-the first occurring in the PMAF immediately after it was seen and the second, ∼2 min later, following almost the same route. This observation provides evidence that one PMAF could reflect double FTEs-there is not always a one-to-one correspondence between FTEs and PMAFs. Reconnection on the dayside magnetopause would be modulated with a period of ∼2 min during the course of transient reconnection. © 2012. American Geophysical Union. All Rights Reserved.
Scientific journal, English - Simultaneous ground-satellite observations of meso-scale auroral arc undulations
T. Motoba; K. Hosokawa; Y. Ogawa; N. Sato; A. Kadokura; S. E. Milan; M. Lester
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 117, 6, 2012, Peer-reviwed, We present simultaneous ground-based and in situ measurements of a train of meso-scale (about 100-300 km) auroral arc undulations, occurring in the postmidnight sector (∼1 MLT) between 0040 UT and 0054 UT on September 21, 2009. The undulations appeared at the auroral poleward boundary, and then moved eastward with a speed of 0.9-2.2 km s-1. Dynamic behaviors of the associated meso-scale ionospheric plasma flows and current systems were also detected with the ground-based magnetometer and radar measurements within the all-sky camera field-of-view. During the interval of interest, simultaneous Cluster observations in the central near tail region (11-14 RE down tail) were available, and especially the ionospheric footprint of Cluster 2 (CL2) was close to the optical auroral forms. CL2 observed strong fluctuations in the in situ magnetic field with amplitude of 5-10 nT whenever a bright arc area, and its trailing adjacent area, of the auroral undulations passed its ionospheric footprint. Such in situ magnetic field changes at CL2 could be considered as a manifestation of localized upward and downward field-aligned current sheets moving eastward at the central near-Earth tail boundary, linked to the meso-scale auroral undulation structures. © 2012. American Geophysical Union. All Rights Reserved.
Scientific journal, English - Ground-based aurora conjugacy and dynamic tracing of geomagnetic conjugate points
Sato, N; A. Kadokura; T. Motoba; K. Hosokawa; G. Bjornsson; T. Saemundsson
Geophys Monograph, edited by A. Keiling, E. Donovan, F. Bagenal and T. Karlsson, AGU, Washington, D.C., 91-98, 2012, Peer-reviwed - Signatures of moving polar cap arcs in the F-region PolarDARN echoes
A. V. Koustov; K. Hosokawa; N. Nishitani; K. Shiokawa; H. Liu
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 30, 3, 441-455, 2012, Peer-reviwed, Joint observations of the all-sky camera at Resolute Bay (Nunavut, Canada) and the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Rankin Inlet and Inuvik (Canada) are considered to establish radar signatures of poleward moving polar cap arcs 'detaching' from the auroral oval. Common features of the events considered are enhanced power or echo occurrence in the wake of the arcs and enhanced spectral width of these echoes. When the arcs were oriented along some of the radar beams, velocity reversals at the arc location were observed with the directions of the arc-associated flows corresponding to a converging electric field. For the event of 9 December 2007, two arcs were poleward progressing almost along the central beams of the Inuvik radar at the speed close to the < B > E </B > x < B > B </B > drift of the bulk of the F-region plasma as inferred from HF Doppler velocities and from independent measurements by the Resolute Bay ionosonde. In global-scale convection maps inferred from all Super Dual Auroral Radar Network (SuperDARN) radar measurements, the polar cap arcs were often seen close to the reversal line of additional mesoscale convection cells located poleward of the normal cells related to the auroral oval.
Scientific journal, English - Decay of polar cap patch
K. Hosokawa; J. I. Moen; K. Shiokawa; Y. Otsuka
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 116, doi:10.1029/2010JA016297, May 2011, Peer-reviwed, We report an event in which a polar cap patch was detected with an all-sky imager (ASI) at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E; AACGM latitude 82.9 degrees), on the nightside. The patch stopped its antisunward motion associated with a northward turning of interplanetary magnetic field and stayed within the field of view of the ASI for more than 1 h. When the patch stagnated, its luminosity decreased gradually, which allows us to investigate how the patch plasma decayed in a quantitative manner. The decay of the patch can be quantitatively explained by the loss through recombinations of O(+) with ambient N(2) and O(2) molecules, if we assume the altitude of the optical patch to be around 295 km. The derived altitude of the patch around 295 km is much higher than the nominal value at 235 km obtained from the MSIS-E90 and IRI-2007 models, indicating that climatological models such as IRI are not suitable for describing the actual density profile of patches. This is probably because the loss process was much faster in the lower-altitude part of the patch; thus, the peak altitude of the patch increased as it traveled across the polar cap because of rapid recombination at the bottomside of the F region. This suggests that we should employ higher emission altitude when we investigate optical patches transported deep into the nightside polar cap. Such information is important when we compare the optical data with other instruments such as coherent radars and GPS scintillation measurements by mapping the all-sky image on the geographic coordinate system with an assumption of the patch emission altitude.
Scientific journal, English - In situ evidence for interplanetary magnetic field induced tail twisting associated with relative displacement of conjugate auroral features
T. Motoba; K. Hosokawa; Y. Ogawa; N. Sato; A. Kadokura; S. C. Buchert; H. Reme
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 116, doi:10.1029/2010JA016206, Apr. 2011, Peer-reviwed, We provide in situ evidence for a twisted near-Earth tail configuration that is responsible for the time sequence of conjugate auroral features associated with relative interhemispheric displacement during a weak substorm, as reported by Motoba et al. (2010). We analyzed the magnetic field data observed using four Cluster satellites in the vicinity of 11-14 R-E central downtail, in close conjunction with the Iceland-Syowa conjugate optical auroral features. Interestingly, we found that the variations in the magnetic field y component (B-y) at all satellites correlated moderately well with the variations in the time-shifted interplanetary magnetic field (IMF) clock angle (theta(CA)). The correlation coefficients (0.56 similar to 0.61) between the B-y field at Cluster and IMF theta(CA) peaked at a time delay of 52 +/- 1 min from the dayside magnetopause, probably corresponding to the time scale for the reconfiguration of the IMF theta(CA) related B-y field in the near-Earth tail. The IMF theta(CA) related B-y variation at Cluster, regarded as a manifestation of the twisting magnetotail configuration, also roughly coincided with the relative magnetic local time displacement of nightside conjugate auroral forms. These results provide strong evidence that the reconfiguration (twisting) process of the near-Earth tail on a relatively longer time scale controls the nightside conjugate auroral locations in both ionospheres.
Scientific journal, English - Midnight sector observations of auroral omega bands
J. A. Wild; E. E. Woodfield; E. Donovan; R. C. Fear; A. Grocott; M. Lester; A. N. Fazakerley; E. Lucek; Y. Khotyaintsev; M. Andre; A. Kadokura; K. Hosokawa; C. Carlson; J. P. McFadden; K. H. Glassmeier; V. Angelopoulos; G. Bjoernsson
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 116, doi:10.1029/2010JA015874, Mar. 2011, Peer-reviwed, We present observations of auroral omega bands on 28 September 2009. Although generally associated with the substorm recovery phase and typically observed in the morning sector, the features presented here occurred just after expansion phase onset and were observed in the midnight sector, dawnward of the onset region. An all-sky imager located in northeastern Iceland revealed that the omega bands were similar to 150 x 200 km in size and propagated eastward at similar to 0.4 km s(-1) while a colocated ground magnetometer recorded the simultaneous occurrence of Ps6 pulsations. Although somewhat smaller and slower moving than the majority of previously reported omega bands, the observed structures are clear examples of this phenomenon, albeit in an atypical location and unusually early in the substorm cycle. The THEMIS C probe provided detailed measurements of the upstream interplanetary environment, while the Cluster satellites were located in the tail plasma sheet conjugate to the ground-based all-sky imager. The Cluster satellites observed bursts of 0.1-3 keV electrons moving parallel to the magnetic field toward the Northern Hemisphere auroral ionosphere; these bursts were associated with increased levels of field-aligned Poynting flux. The in situ measurements are consistent with electron acceleration via shear Alfven waves in the plasma sheet similar to 8 R-E tailward of the Earth. Although a one-to-one association between auroral and magnetospheric features was not found, our observations suggest that Alfven waves in the plasma sheet are responsible for field-aligned currents that cause Ps6 pulsations and auroral brightening in the ionosphere. Our findings agree with the conclusions of earlier studies that auroral omega bands have a source mechanism in the midtail plasma sheet.
Scientific journal, English - Decay of polar cap patch
K. Hosokawa; J. I. Moen; K. Shiokawa; Y. Otsuka
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 116, 5, 2011, Peer-reviwed, We report an event in which a polar cap patch was detected with an all-sky imager (ASI) at Resolute Bay, Canada (74.73° N, 265.07° E
AACGM latitude 82.9°), on the nightside. The patch stopped its antisunward motion associated with a northward turning of interplanetary magnetic field and stayed within the field of view of the ASI for more than 1 h. When the patch stagnated, its luminosity decreased gradually, which allows us to investigate how the patch plasma decayed in a quantitative manner. The decay of the patch can be quantitatively explained by the loss through recombinations of O+ with ambient N2 and O2 molecules, if we assume the altitude of the optical patch to be around 295 km. The derived altitude of the patch around 295 km is much higher than the nominal value at 235 km obtained from the MSIS-E90 and IRI-2007 models, indicating that climatological models such as IRI are not suitable for describing the actual density profile of patches. This is probably because the loss process was much faster in the lower-altitude part of the patch
thus, the peak altitude of the patch increased as it traveled across the polar cap because of rapid recombination at the bottomside of the F region. This suggests that we should employ higher emission altitude when we investigate optical patches transported deep into the nightside polar cap. Such information is important when we compare the optical data with other instruments such as coherent radars and GPS scintillation measurements by mapping the all-sky image on the geographic coordinate system with an assumption of the patch emission altitude. Copyright 2011 by the American Geophysical Union.
Scientific journal, English - In situ evidence for interplanetary magnetic field induced tail twisting associated with relative displacement of conjugate auroral features
T. Motoba; K. Hosokawa; Y. Ogawa; N. Sato; A. Kadokura; S. C. Buchert; H. Réme
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 116, 4, 2011, Peer-reviwed, We provide in situ evidence for a twisted near-Earth tail configuration that is responsible for the time sequence of conjugate auroral features associated with relative interhemispheric displacement during a weak substorm, as reported by Motoba et al. (2010). We analyzed the magnetic field data observed using four Cluster satellites in the vicinity of 11-14 RE central downtail, in close conjunction with the Iceland-Syowa conjugate optical auroral features. Interestingly, we found that the variations in the magnetic field y component (By) at all satellites correlated moderately well with the variations in the time-shifted interplanetary magnetic field (IMF) clock angle (θCA). The correlation coefficients (0.56 ∼ 0.61) between the By field at Cluster and IMF θCA peaked at a time delay of 52 1 min from the dayside magnetopause, probably corresponding to the time scale for the reconfiguration of the IMF θCA related By field in the near-Earth tail. The IMF θCA related By variation at Cluster, regarded as a manifestation of the twisting magnetotail configuration, also roughly coincided with the relative magnetic local time displacement of nightside conjugate auroral forms. These results provide strong evidence that the reconfiguration (twisting) process of the near-Earth tail on a relatively longer time scale controls the nightside conjugate auroral locations in both ionospheres. Copyright 2011 by the American Geophysical Union.
Scientific journal, English - Motion of polar cap arcs
K. Hosokawa; J. I. Moen; K. Shiokawa; Y. Otsuka
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 116, 1, doi:10.1029/2010JA015906, 2011, Peer-reviwed, A statistics of motion of polar cap arcs is conducted by using 5 years of optical data from an all-sky imager at Resolute Bay, Canada (74.73°N, 265.07°E). We identified 743 arcs by using an automated arc detection algorithm and statistically examined their moving velocities as estimated by the method of Hosokawa et al. (2006). The number of the arcs studied is about 5 times larger than that in the previous statistics of polar cap arcs by Valladares et al. (1994)
thus, we could expect to obtain more statistically significant results. Polar cap arcs are found to fall into two distinct categories: the By-dependent and By-independent arcs. The motion of the former arcs follows the rule reported by Valladares et al. (1994), who showed that stable polar cap arcs move in the direction of the interplanetary magnetic field (IMF) By. About two thirds of the arcs during northward IMF conditions belong to this category. The latter arcs always move poleward irrespective of the sign of the IMF By, which possibly correspond to the poleward moving arcs in the morning side reported by Shiokawa et al. (1997). At least one third of the arcs belong to this category. The By-dependent arcs tend to move faster when the magnitude of the IMF By is larger, suggesting that the transport of open flux by lobe reconnection from one polar cap compartment to the other controls their motion. In contrast, the speed of the By-independent arcs does not correlate with the magnitude of the By. The motions of both the B y-dependent and By-independent arcs are most probably caused by the magnetospheric convection. Convection in the region of B y-dependent arcs is affected by the IMF By, which indicates that their sources may be on open field lines or in the closed magnetosphere adjacent to the open-closed boundary, whereas B y-independent arcs seem to be well on closed field lines. Hence, the magnetospheric source of the two types of arc may be different. This implies that the mechanisms causing the motion and generation of arcs could be different between the two types of polar cap arc. Copyright 2011 by the American Geophysical Union.
Scientific journal, English - A powerful tool for browsing quick-look data in solar-terrestrial physics: "Conjunction Event Finder"
Yukinaga Miyashita; Iku Shinohara; Masaki Fujimoto; Hiroshi Hasegawa; Keisuke Hosokawa; Taku Takada; Tomoaki Hori
EARTH PLANETS AND SPACE, TERRA SCIENTIFIC PUBL CO, 63, 1, E1-E4, 2011, Peer-reviwed, The "Conjunction Event Finder (CEF)" is a Web tool for seamlessly browsing quick-look (QL) data from many different kinds of satellites and ground-based instruments in solar-terrestrial physics. The QL plots are generally scattered all over the world, so that browsing many of them is so far very troublesome and inefficient. Just a simple procedure on the CEF, however, generates a collection of links to the QL plots for a period of interest, allowing us to check the data much more efficiently than ever. Hence this tool is powerful in finding interesting events of conjunction observations by satellites and ground-based instruments. The CEF is available in the Data ARchives and Transmission System (DARTS) at Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA) in Japan.
Scientific journal, English - Propagation of large amplitude ionospheric disturbances with velocity dispersion observed by the SuperDARN Hokkaido radar after the 2011 off the Pacific coast of Tohoku Earthquake
Nozomu Nishitani; Tadahiko Ogawa; Yuichi Otsuka; Keisuke Hosokawa; Tomoaki Hori
EARTH PLANETS AND SPACE, TERRA SCIENTIFIC PUBL CO, 63, 7, 891-896, 2011, Peer-reviwed, Ionospheric responses to the 2011 off the Pacific coast of Tohoku Earthquake are studied using the SuperDARN Hokkaido radar, which is located at (43.5 degrees N, 143.6 degrees E) and which monitors the ionosphere over a wide horizontal area. The radar observed an oscillation of the vertical motion of the ionosphere with a period of about 1 to 2 min. The disturbance propagated northward, away from the epicenter with the velocity of about 6.2, 4.5, 3.9 and 3.5 km/s. The latter three values are basically consistent with the propagation of the Earth's surface waves reported in several previous studies. The propagation velocities decreased with time, which has not been reported in previous studies for this propagation velocity range. The peak-to-peak amplitudes of Doppler velocities of ground/sea scatter echoes observed by the radar were up to 200 m/s, which is considerably larger than previously-reported values using HF Doppler measurements, although they are not extremely large for this historical earthquake (M = 9.0). This is the first time that ionospheric data have been obtained with high temporal (8 s) and spatial (22.5 km) resolutions following a giant earthquake, which enables us to discuss the detailed characteristics of the propagation of coseismic ionospheric disturbances.
Scientific journal, English - Dynamic temporal evolution of polar cap tongue of ionization during magnetic storm
K. Hosokawa; T. Tsugawa; K. Shiokawa; Y. Otsuka; N. Nishitani; T. Ogawa; M. R. Hairston
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, doi:10.1029/2010JA015848, Dec. 2010, Peer-reviwed, During a magnetic storm on 14-16 December 2006, a polar cap tongue of ionization (TOI) was detected by an all-sky imager (ASI) at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E). We investigate the temporal evolution and spatial structure of the TOI in detail by combining the optical data with other observations (e. g., solar wind, GPS total electron content, SuperDARN, and DMSP and NOAA POES satellites). The TOI was observed as a bright and elongated 630 nm airglow plume for 4 h during the main phase of the storm. This interval corresponded to a period of prolonged stable large-amplitude southward IMF during a coronal mass ejection (CME). One to one and a half hours before the appearance of TOI, the polar cap boundary expanded rapidly far equatorward, and a positive ionospheric storm occurred. This implies that both the "expansion of the high-latitude plasma convection" and "build up of the source plasma in the midlatitudes" are necessary conditions for the formation of a TOI. Because both of them were triggered by a major southward turning of the IMF, the prolonged large-amplitude southward IMF orientation in the trailing part of the CME was primarily responsible for the generation of TOI. After its appearance, the TOI exhibited dynamic motion in the dawn to dusk direction. Simultaneous SuperDARN data suggest that a longitudinal progression of subauroral polarization stream controlled this dynamic motion. The optical TOI was found to be a continuous stream elongated in the noon-midnight direction although it contained some mesoscale patterns. Absence of large-scale temporal changes in the cusp plasma flow during the stable IMF period allowed the TOI to remain continuous without being broken into polar cap patches. The mesoscale structures within the TOI were probably produced by small-scale velocity fluctuations in the cusp plasma flow. The TOI as visualized with the all-sky airglow imager was found to be much more dynamic and much more complicated than we ever thought. The current study indicates that such a behavior of the TOI was presumably caused by a combination of temporal variations in the global-scale plasma circulation system, expansion and contraction of the polar cap area, and plasma density changes in the dayside low to midlatitudes.
Scientific journal, English - Preonset time sequence of auroral substorms: Coordinated observations by all-sky imagers, satellites, and radars
Y. Nishimura; L. R. Lyons; S. Zou; X. Xing; V. Angelopoulos; S. B. Mende; J. W. Bonnell; D. Larson; U. Auster; T. Hori; N. Nishitani; K. Hosokawa; G. Sofko; M. Nicolls; C. Heinselman
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, doi:10.1029/2010JA015832, Nov. 2010, Peer-reviwed, Using two conjunction events of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) imagers and spacecraft as well as the Super Dual Auroral Radar Network (SuperDARN) and Poker Flat Incoherent Scatter Radars, we show that longitudinally narrow flow bursts in the nightside polar cap can precede poleward boundary intensifications (PBIs) that are followed by equatorward moving north-south (N-S) arcs, including those leading to substorm onset instability within the near-Earth plasma sheet. The association between the ionospheric flows and PBIs indicates that enhanced flows on open field lines may contribute to parallel potential drop increase, triggering of magnetotail reconnection, and to the earthward flows leading to N-S arcs and to substorm onset. We also investigated differences between N-S arc sequences that do and do not lead to substorm expansion onset. We found that the two types of N-S arcs have similar characteristics, indicating that their corresponding plasma sheet flow properties could also be similar. There is, however, one difference between the sequences of N-S arc evolution. Each N-S arc leads to small intensification of the growth phase arc, and when the onset-related N-S arc reaches the equatorward portion of the auroral oval, the preexisting growth phase arc is much brighter than at the times of non-onset-related N-S arcs. Assuming that the growth phase arc is related to pressure gradients at the inner edge of the plasma sheet, this difference indicates that the near-Earth plasma pressure distribution at the time of plasma sheet fast flows is crucial in substorm triggering. These observations suggest that substorm onset instability is possible only when the preexisting inner plasma sheet pressure is sufficiently large.
Scientific journal, English - Plasma flow during the brightening of proton aurora in the cusp
S. Taguchi; K. Hosokawa; S. Suzuki; A. Tawara; H. U. Frey; J. Matzka; A. S. Yukimatu; N. Sato
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, Oct. 2010, Peer-reviwed, On the basis of simultaneous observations from the Super Dual Auroral Radar Network (SuperDARN), the far ultraviolet instrument on the IMAGE spacecraft, and a magnetometer installed on the east coast of Greenland, we present the characteristics of plasma flow during a westward moving proton aurora in the cusp, observed on 28 July 2000. Data with a time resolution of 12 and 25 s from SuperDARN at pykkvibaer, Iceland, show that the flow having a poleward component, which was accompanied by a quick equatorward expansion of the flow region, occurred in the early stages (approximately 1.5 min) of the brightening. Data from the magnetometer from a ground station on the Greenland east coast, which is located a few hundred kilometers west of the radar's field of view, show perturbations that are consistent with equatorward flow overhead, coincident with the expansion. The presence of flow vectors in opposite directions suggests that vortical flow was present during the proton aurora. Evidence supporting the suggested flow pattern has been found in an event recorded by the Greenland west coast magnetometer chain and in a cusp pass of the DE 2 spacecraft in the literature. We attribute the moving proton aurora to the traveling bulge at the polar cap boundary, which is the footprint of a flux transfer event, and imply that the preexisting vortical flow may be intensified when it becomes inflow to the bulge.
Scientific journal, English - Plasma flow during the brightening of proton aurora in the cusp
Taguchi, S; K. Hosokawa; S. Suzuki; A. Tawara; H. U. Frey; J. Matzka; A. S. Yukimatu; N. Sato
J. Geophys. Res., 115, A10308, Oct. 2010, Peer-reviwed, On the basis of simultaneous observations from the Super Dual Auroral Radar Network (SuperDARN), the far ultraviolet instrument on the IMAGE spacecraft, and a magnetometer installed on the east coast of Greenland, we present the characteristics of plasma flow during a westward moving proton aurora in the cusp, observed on 28 July 2000. Data with a time resolution of 12 and 25 s from SuperDARN at Þykkvibær, Iceland, show that the flow having a poleward component, which was accompanied by a quick equatorward expansion of the flow region, occurred in the early stages (approximately 1.5 min) of the brightening. Data from the magnetometer from a ground station on the Greenland east coast, which is located a few hundred kilometers west of the radar's field of view, show perturbations that are consistent with equatorward flow overhead, coincident with the expansion. The presence of flow vectors in opposite directions suggests that vortical flow was present during the proton aurora. Evidence supporting the suggested flow pattern has been found in an event recorded by the Greenland west coast magnetometer chain and in a cusp pass of the DE 2 spacecraft in the literature. We attribute the moving proton aurora to the traveling bulge at the polar cap boundary, which is the footprint of a flux transfer event, and imply that the preexisting vortical flow may be intensified when it becomes inflow to the bulge.
Scientific journal, English - Plasma irregularities adjacent to auroral patches in the postmidnight sector
K. Hosokawa; T. Motoba; A. S. Yukimatu; S. E. Milan; M. Lester; A. Kadokura; N. Sato; G. Bjornsson
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, doi:10.1029/2010JA015319, Sep. 2010, Peer-reviwed, We demonstrate a close association between decameter-scale plasma irregularities in the E region ionosphere and auroral patches in the postmidnight sector. In September 2009, campaign-based measurements of the aurora were conducted in Iceland with a white light all-sky camera (ASC) at Tjornes (66.20 degrees N, 17.12 degrees W) and the SuperDARN radar at _ykkvibaer (63.77 degrees N, 20.54 degrees W). On one night during the campaign period, the ASC observed the successive passage of auroral patches in the postmidnight sector after a small substorm-like activity. The patches were drifting predominantly eastward across the field-of-view of the ASC with a speed of approximately 360-450 m s(-1), which is consistent with the sunward convection in the postmidnight westward electrojet. The simultaneous radar measurements recorded strong radar backscatter echoes (> 15 dB) within the gaps between adjacent auroral patches, while such echoes were not observed or were very weak in the region of the aurora. The Doppler velocity estimation showed that the electric field was clearly reduced within the patches, which was probably the result of the enhanced conductance associated with auroral precipitation. Thus, this reduction in the electric field suppressed the generation of irregularities (i.e., radar echoes) in the regions of auroral patches. This suggests that the conductance enhancement associated with precipitating electrons not only modified the electric field within the aurora but also affected the generation of small-scale plasma structures in the vicinity of the patch-type optical auroral forms.
Scientific journal, English - Varying interplanetary magnetic field B-y effects on interhemispheric conjugate auroral features during a weak substorm
T. Motoba; K. Hosokawa; N. Sato; A. Kadokura; G. Bjornsson
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, doi:10.1029/2010JA015369, Sep. 2010, Peer-reviwed, Interhemispheric conjugate auroral features during a weak substorm interval were investigated using simultaneous all-sky camera (ASC) measurements at the northern and southern geomagnetic conjugate points at Tjornes (TJO; 66.2 degrees N, 342.9 degrees E) in Iceland and Syowa Station (SYO; 69.0 degrees S, 39.6 degrees E) in Antarctica. Around postmidnight, just after the substorm onset, the ASC field of view (FOV) at TJO was first filled with dynamic auroral activations; however, its counterpart was not detected over the zenith at SYO at that time. In contrast, in the late stage (about 20 min after the onset) of substorm development we observed spiral-like auroral arcs with a similar shape drifting eastward across the center of each ASC FOV, although the one at TJO preceded the one at SYO. The time sequence of the interhemispheric conjugate auroral features was well reflected in the geomagnetic field variations at both stations. On the basis of a detailed comparison of both ASC images, we identified that the northern geomagnetic footprint of SYO was displaced poleward of TJO by up to 3.0 degrees or more in the initial stage of substorm development, whereas in the late stage it was displaced eastward by up to similar to 1 h relative to TJO and then moved closer to TJO. We emphasize that the dynamic motion of the conjugate points is a consequence of the time-dependent magnetotail field reconfiguration process, controlled by the varying interplanetary magnetic field B-y polarity.
Scientific journal, English - A new SuperDARN high temporal resolution 2-D ionospheric / thermospheric observation with simultaneous optical measurements and its contributions to CAWSES-II
Yukimatu, A. S; K. Hosokawa; T. Motoba; N. Sato; M. Lester
Proc. CAWSES-II Kickoff Symposium in Japan, 103-106, Jul. 2010
International conference proceedings, English - Plasma irregularities in the duskside subauroral ionosphere as observed with midlatitude SuperDARN radar in Hokkaido, Japan
K. Hosokawa; N. Nishitani
RADIO SCIENCE, AMER GEOPHYSICAL UNION, 45, doi:10.1029/2009RS004244, Jul. 2010, Peer-reviwed, We revealed the spatial distribution of HF radar echoes in the subauroral region by conducting a statistical analysis of scattering occurrence from the midlatitude Super Dual Auroral Radar Network (SuperDARN) radar in Hokkaido, Japan. Consequently, Dusk Scatter Event (DUSE) was identified as a most prominent backscatter target in these latitudes. Past studies have intended to associate an appearance of DUSE with the density gradient at the poleward or sunward edges of the midlatitude trough. However, exact spatial collocation between the source region of DUSE and the midlatitude trough has not been revealed because the SuperDARN radars in the auroral region could not observe the whole part of DUSE due to a limitation of the field-of -view coverage. Thus, it has been unclear which of the density gradients associated with the midlatitude trough is responsible for generating DUSE. The data from the Hokkaido radar enabled us to estimate the lower-latitude boundary of DUSE as around 59 degrees in AACGM magnetic latitude. In addition, by adding the data from the King Salmon radar in Alaska we derived a complete statistical distribution of DUSE. The latitudinal extent of DUSE is about 9 degrees from 59 degrees to 68 degrees, which is approximately 1000 km. The statistical distribution of DUSE was compared with the model of the midlatitude trough. As a result, the source region of DUSE is closely colocated with the minimum of the trough, which suggests that the electron density gradient at the sunward edge of the trough is responsible for DUSE. This means that the location of the duskside sunward edge (i.e., local time extent) of the midlatitude trough can be monitored by using an appearance of DUSE as a proxy. The current statistical analysis also suggests that we can derive a spatial distribution of HF radar echoes from the midlatitudes to high latitudes by combining the data from the Hokkaido and King Salmon radars located in the Far Eastern area, which would be a very powerful diagnostic tool for investigating the global distribution of plasma irregularities.
Scientific journal, English - Development of CDF conversion scheme for SDD fitacf files by ERG-Science Center: A new data analysis platform powered by the THEMIS tool
Hori, T; N. Nishitani; Y. Miyashita; Y. Miyoshi; K. Seki; T. Segawa; K. Hosokawa; A. S. Yukimatu; Y. Tanaka; N. Sato; M. Kunitake; T. Nagatsuma
Proc. SuperDARN Workshop 2010 in Hermanus, South Africa, Jun. 2010
International conference proceedings, English - 2-D Electric field modulation with pulsating aurora observed with a new SuperDARN high temporal resolution technique
Yukimatu, A. S; K. Hosokawa; T. Motoba; N. Sato; M. Lester
Proc. SuperDARN Workshop 2010 in Hermanus, South Africa, 3-8-1-3-8-30, Jun. 2010
International conference proceedings, English - Large-scale traveling ionospheric disturbance observed by superDARN Hokkaido HF radar and GPS networks on 15 December 2006
H. Hayashi; N. Nishitani; T. Ogawa; Y. Otsuka; T. Tsugawa; K. Hosokawa; A. Saito
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, doi:10.1029/2009JA014297, Jun. 2010, Peer-reviwed, On 15 December 2006, during the main phase of a relatively large storm, Doppler velocity data from the Super Dual Aural Radar Network (SuperDARN) Hokkaido radar, together with total electron content (TEC) data from the GPS Earth Observation Network (GEONET), recorded daytime large-scale traveling ionospheric disturbances (LSTIDs). We studied two disturbances propagating southward and one disturbance propagating northward between 0000 and 0600 UT on 15 December 2006. The former disturbances were LSTIDs typical of those reported in many previous studies, whereas the latter was confirmed as an LSTID propagating from the Southern into the Northern Hemisphere, reported in a few past studies. From comparisons of SuperDARN Hokkaido radar Doppler velocity and GEONET TEC, we found a positive correlation between downward ionospheric motion and increasing TEC. This relationship is consistent with results of model calculation. This is the first observation of LSTIDs ranging from high to low latitude combining simultaneous SuperDARN HF radar and GPS network observations.
Scientific journal, English - Initial development of HF radar polar patch caused by azimuthal flow burst in the cusp
S. Taguchi; K. Hosokawa; S. Suzuki; A. S. Yukimatu; N. Sato
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, May 2010, Peer-reviwed, In this study, we report evidence proving the existence of a close relationship between the initial development of a poleward propagating feature of the HF radar backscatter, that is, HF radar polar patch, and a fast azimuthal flow in the cusp. We focus on two events in which the HF radar polar patch was formed and was identified by the Super Dual Auroral Radar Network radars at Saskatoon, Canada, and Prince George, Canada, on 27 March 2001. We examine their spatial and temporal development. The two events occurred at the interface between the interplanetary magnetic field (IMF) B(Y)-controlled azimuthal flow and the antisunward flow typical of a negative IMF B(Z); they developed in a longitudinally asymmetric manner. The increase in vertical bar BY/BZ vertical bar when B(Z) was negative triggered the fast azimuthal flow. We interpret the temporal and spatial development of the HF radar polar patch in terms of the plasma density gradient created by the azimuthal flow and in terms of the subsequent development of the gradient in the direction of both the azimuthal flow and the antisunward flow.
Scientific journal, English - Initial development of HF radar polar patch caused by azimuthal flow burst in the cusp
Taguchi, S; K. Hosokawa; S. Suzuki; A. S. Yukimatu; N. Sato
J. Geophys. Res., 115, A05305, May 2010, Peer-reviwed, In this study, we report evidence proving the existence of a close relationship between the initial development of a poleward propagating feature of the HF radar backscatter, that is, HF radar polar patch, and a fast azimuthal flow in the cusp. We focus on two events in which the HF radar polar patch was formed and was identified by the Super Dual Auroral Radar Network radars at Saskatoon, Canada, and Prince George, Canada, on 27 March 2001. We examine their spatial and temporal development. The two events occurred at the interface between the interplanetary magnetic field (IMF) BY-controlled azimuthal flow and the antisunward flow typical of a negative IMF BZ; they developed in a longitudinally asymmetric manner. The increase in ∣BY/BZ∣ when BZ was negative triggered the fast azimuthal flow. We interpret the temporal and spatial development of the HF radar polar patch in terms of the plasma density gradient created by the azimuthal flow and in terms of the subsequent development of the gradient in the direction of both the azimuthal flow and the antisunward flow.
Scientific journal, English - Dynamic temporal evolution of polar cap tongue of ionization during magnetic storm
K. Hosokawa; T. Tsugawa; K. Shiokawa; Y. Otsuka; N. Nishitani; T. Ogawa; M. R. Hairston
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 12, 2010, Peer-reviwed, During a magnetic storm on 14-16 December 2006, a polar cap tongue of ionization (TOI) was detected by an all-sky imager (ASI) at Resolute Bay, Canada (74.73°N, 265.07°E). We investigate the temporal evolution and spatial structure of the TOI in detail by combining the optical data with other observations (e.g., solar wind, GPS total electron content, SuperDARN, and DMSP and NOAA POES satellites). The TOI was observed as a bright and elongated 630 nm airglow plume for 4 h during the main phase of the storm. This interval corresponded to a period of prolonged stable large-amplitude southward IMF during a coronal mass ejection (CME). One to one and a half hours before the appearance of TOI, the polar cap boundary expanded rapidly far equatorward, and a positive ionospheric storm occurred. This implies that both the "expansion of the high-latitude plasma convection" and "build up of the source plasma in the midlatitudes" are necessary conditions for the formation of a TOI. Because both of them were triggered by a major southward turning of the IMF, the prolonged large-amplitude southward IMF orientation in the trailing part of the CME was primarily responsible for the generation of TOI. After its appearance, the TOI exhibited dynamic motion in the dawn to dusk direction. Simultaneous SuperDARN data suggest that a longitudinal progression of subauroral polarization stream controlled this dynamic motion. The optical TOI was found to be a continuous stream elongated in the noon-midnight direction although it contained some mesoscale patterns. Absence of large-scale temporal changes in the cusp plasma flow during the stable IMF period allowed the TOI to remain continuous without being broken into polar cap patches. The mesoscale structures within the TOI were probably produced by small-scale velocity fluctuations in the cusp plasma flow. The TOI as visualized with the all-sky airglow imager was found to be much more dynamic and much more complicated than we ever thought. The current study indicates that such a behavior of the TOI was presumably caused by a combination of temporal variations in the global-scale plasma circulation system, expansion and contraction of the polar cap area, and plasma density changes in the dayside low to midlatitudes. Copyright 2010 by the American Geophysical Union.
Scientific journal, English - Plasma irregularities adjacent to auroral patches in the postmidnight sector
K. Hosokawa; T. Motoba; A. S. Yukimatu; S. E. Milan; M. Lester; A. Kadokura; N. Sato; G. Bjornsson
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 9, 2010, Peer-reviwed, We demonstrate a close association between decameter-scale plasma irregularities in the E region ionosphere and auroral patches in the postmidnight sector. In September 2009, campaign-based measurements of the aurora were conducted in Iceland with a white light all-sky camera (ASC) at Tjrnes (66.20N, 17.12W) and the SuperDARN radar at ykkvibaer (63.77N, 20.54W). On one night during the campaign period, the ASC observed the successive passage of auroral patches in the postmidnight sector after a small substorm-like activity. The patches were drifting predominantly eastward across the field-of-view of the ASC with a speed of approximately 360-450 m s-1, which is consistent with the sunward convection in the postmidnight westward electrojet. The simultaneous radar measurements recorded strong radar backscatter echoes (>
15 dB) within the gaps between adjacent auroral patches, while such echoes were not observed or were very weak in the region of the aurora. The Doppler velocity estimation showed that the electric field was clearly reduced within the patches, which was probably the result of the enhanced conductance associated with auroral precipitation. Thus, this reduction in the electric field suppressed the generation of irregularities (i.e., radar echoes) in the regions of auroral patches. This suggests that the conductance enhancement associated with precipitating electrons not only modified the electric field within the aurora but also affected the generation of small-scale plasma structures in the vicinity of the patch-type optical auroral forms. © Copyright 2010 by the American Geophysical Union.
Scientific journal, English - Reorganization of polar cap patches through shears in the background plasma convection
K. Hosokawa; J. -P. St-Maurice; G. J. Sofko; K. Shiokawa; Y. Otsuka; T. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, doi:10.1029/2009JA014599, Jan. 2010, Peer-reviwed, On the night of December 20, 2006, 630 nm airglow images obtained by an all-sky camera at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E; altitude adjusted corrected geomagnetic (AACGM) latitude 82.9 degrees) showed the passage of successive polar cap patches. Shortly after convection came to a temporary halt, one of the patches was reorganized into two substructures in approximately 8 min. The two-dimensional background ionospheric convection pattern measured using the newly deployed PolarDARN radar at Rankin Inlet (62.82 degrees N, 93.11 degrees W; AACGM latitude 72.96 degrees) showed that a velocity shear of approximately 120 m s(-1)/340 km suddenly appeared in the vicinity of the patch at the time of reorganization. A qualitative analysis of the relationship between the magnitude of the velocity shear and the distance between the divided patches indicates that the shear in the background plasma convection velocity significantly contributed to the reorganization of the patch. This shear structure appeared soon after a southward turning of the interplanetary magnetic field (IMF) and was probably associated with the reconfiguration of the convection pattern from a pre-existing northward-oriented IMF pattern to a southward-oriented one. The present observations indicate that the reconfiguration/deformation of patches because of a shear in the background convection field, especially reorganization of patches into smaller substructures, may play an important role in the rapid structuring of patches.
Scientific journal, English - Modulation of ionospheric conductance and electric field associated with pulsating aurora
K. Hosokawa; Y. Ogawa; A. Kadokura; H. Miyaoka; N. Sato N.
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 3, doi:10.1029/2009JA014683, 2010, Peer-reviwed, We present, for the first time, a quasiperiodic modulation of ionospheric parameters, associated with the occurrence of pulsating auroras, such as electron density, conductance, and electric field. In March 2008, simultaneous campaign-based measurements of pulsating auroras were conducted over Tromsø (69.60°N, 19.20°E), Norway, using an all-sky TV camera (ATV) and the European Incoherent Scatter (EISCAT) UHF system. During an interval within this campaign period, pulsating auroras, with periods of 8-17 s, were observed by the ATV in the morning local time sector (̃0500 MLT). In this interval, quasiperiodic oscillations were identified in the raw electron density obtained by EISCAT. The electron density at lower altitudes in the E region (95-115 km) was enhanced by a factor of 3-4 immediately after the optical pulsation became "on." The height-integrated Hall conductance was also elevated, by a factor of 1.5-2, almost in harmony with the electron density variation. The response of the electron density and Hall conductance to the appearance of the pulsating aurora was almost immediate. However, both did not decrease to the background level promptly after optical pulsation ceased. This was primarily because it took a few seconds for the electron density to decrease through recombination with ambient ions at these altitudes. Interestingly, electric field measurements performed by the remote antenna at Kiruna showed that redirection of the electric field occurred when the pulsating aurora was "on." We propose a model in which the enhancement of Hall conductance within patches of the pulsating aurora caused charge accumulation at the edges of the patches, and the electric field was then modified by the resulting polarization electric field. An estimation of the electric field modulation with this model well reproduced the actual electric field observations carried out by EISCAT, which confirmed the validity of the model. These results imply that the ionization caused by high-energy electron precipitation associated with a pulsating aurora has a significant effect on the ionospheric conductivity and current system. This modification of the ionosphere may facilitate characterization of the morphological features of pulsating auroras. In particular, modification of the electric field would affect the spatial structure of pulsating aurora patches, such as their motion and shapes.
Scientific journal, English - Initial development of the HF radar polar patch driven by the azimuthal flow burst in the cusp
Taguchi S; K. Hosokawa; S. Suzuki; A. S. Yukimatu; N. Sato
Journal of Geophysical Research, 115, doi:10.1029/2009JA014631, 2010, Peer-reviwed
Scientific journal, English - Pedersen current carried by electrons in auroral D-region
Hosokawa, K; Y. Ogawa
Geophysical Research Letters, 37, doi:10.1029/2010GL044746, 2010, Peer-reviwed
Scientific journal, English - Distorted flow during moving mesoscale plasma precipitation in the cusp
Taguchi, S; K. Hosokawa; S. Suzuki; A. Tawara; H. U. Frey; J. Mazka; A. S. Yukimatu; N. Sato
Journal of Geophysical Research, 115, doi:10.1029/2010JA015535, 2010, Peer-reviwed
Scientific journal, English - GPS total electron content variations associated with a polar cap arc
P. T. Jayachandran; K. Hosokawa; J. W. MacDougall; S. Mushini; R. B. Langley; K. Shiokawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2009JA014916, Dec. 2009, Peer-reviwed, We report an example of total electron content (TEC) variations, using Global Positioning System (GPS) measurements, associated with a polar cap arc detected by an all-sky imager and ionosonde at a polar cap station. During the transit of the arc, GPS signals along the arc length showed an increase of similar to 2 TEC units whereas GPS signals perpendicular to the arc showed only an increase of similar to 0.3 TEC units. This indicates that the GPS TEC variations associated with a polar cap arc are dependent on the geometry of the GPS raypaths with respect to the arc. Ionosonde measurements confirm that this arc was an E region feature at similar to 110 km with peak electron density of 5.4 x 10(11) el/m(3). Estimated speed of the arc using a GPS triangulation method was about 300 m/s.
Scientific journal, English - Ion heating in high-speed flow channel within the duskside cell of the polar cap ion convection under large IMF-B-y condition
Sawako Maeda; Yasunobu Ogawa; Keisuke Hosokawa; Satonori Nozawa; Shin-ichiro Oyama; Takuo Tsuda; Asgeir Brekke
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2009JA014300, Nov. 2009, Peer-reviwed, F region strong sunward ion flow embedded in the duskside cell of expanding polar cap ion convection and coincidental increase in the ion temperature were observed from about 73 degrees to 69 degrees in geomagnetic latitude between 16: 00 and 16: 48 MLT on 19 August, 2006 from an experiment using the European Incoherent Scatter (EISCAT) radars at Tromso, Sodankyla and Longyearbyen together with the CUTLASS HF radars. The spatiotemporal structure of the convection map obtained by the SuperDARN HF radars showed that the high-speed flow channel elongated in 14-17 MLT was moving equatorward. The flow channel appeared during an interval of negative interplanetary magnetic field B-z associated with large positive B-y. In order to evaluate ion frictional heating and resultant ion temperature increase quantitatively, the experiment was conducted to estimate the ion velocity vector and the ion temperature at the common scattering volume of the EISCAT radars. While the flow channel moved equatorward, the ion temperature increase became less evident at higher part of latitudes within the flow channel, which means that ion frictional heating was depressed where the neutral gases had already responded to the high-speed ions. The increase in the ion temperature at particular geomagnetic latitude continued for about 20 min, and then ceased while the ion velocity was still enhanced. Ion frictional heating lasted until the neutral wind was accelerated to the equivalent level of the surrounded ion flow.
Scientific journal, English - Coordinated observations of nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow and HF radar echoes at midlatitudes
S. Suzuki; K. Hosokawa; Y. Otsuka; K. Shiokawa; T. Ogawa; N. Nishitani; T. F. Shibata; A. V. Koustov; B. M. Shevtsov
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2008JA013963, Jul. 2009, Peer-reviwed, We investigate nighttime medium-scale traveling ionospheric disturbances (MSTIDs) using the SuperDARN HF radar at Hokkaido, Japan (43.5 degrees N, 143.6 degrees E), and an OI 630-nm airglow imager located at Paratunka, Russia (53.0 degrees N, 158.2 degrees E), within the radar field of view. The imager identified southwestward propagating MSTIDs with a horizontal wavelength of similar to 300 km on 8 December 2007. Throughout this event, the radar continuously detected ionospheric echoes originating from decameter-scale field-aligned irregularities (FAIs) at the F region heights. The Doppler velocities of these echoes showed systematic polarity changes which were consistent with airglow intensity variations. These polarity changes would be attributed to E x B plasma drifts caused by the polarization electric field embedded in the MSTIDs. The FAI echo powers also varied in agreement with the airglow intensity variations: strong (weak) echoes coincided with the airglow depletion (enhancement) region. Considering the MSTID polarization electric field, it is suggested that the observed FAIs were generated by the gradient drift instability on the bottomside of the F region.
Scientific journal, English - Moving mesoscale plasma precipitation in the cusp
S. Taguchi; S. Suzuki; K. Hosokawa; Y. Ogawa; A. S. Yukimatu; N. Sato; M. R. Collier; T. E. Moore
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 114, 6, 01 Jun. 2009, Peer-reviwed, On 28 March 2001, when the interplanetary magnetic field was strongly duskward, the DMSP F12 spacecraft observed an ion precipitation burst in a latitudinally narrow region near 1200 MLT. A few minutes earlier, the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft, whose field of view (FOV) looks into the high-altitude cusp, detected an enhancement of energetic neutral atom signals, which are produced by the ion injection. The LENA data suggest that the ion injection moved out of its FOV after approximately 4 min. At this time, the ground-based magnetometers of the IMAGE chain in Svalbard, located westward of LENA'S FOV, began to indicate perturbations. These perturbations immediately reached a peak and then ceased
the perturbations lasted 2-3 min. During this interval, there was an enhanced westward flow over Svalbard, as observed by the SuperDARN radars. The EISCAT Svalbard radar detected an enhancement of electron density and temperature that was concurrent with this flow enhancement, suggesting that a plasma precipitation burst accompanied with the flow. These observations, which cover a longitudinally extending region of the cusp, strongly suggest the existence of moving mesoscale plasma precipitation (MMPP). The MMPP travels westward with a longitudinally elongated form. Its leading and trailing edges should be created by the temporal effect of the cusp. The other edges, which lie along the streamline, would originate in a spatially limited region along the open-closed line. The boundary of the MMPP form is delineated by both the temporal and spatial structures of the cusp. Copyright 2009 by the American Geophysical Union.
Scientific journal, English - Simultaneous observations of visible NLC and SuperDARN-PMSE over Japanese Syowa station in Antarctica
Sato, N; K. Hosokawa; Y. Takeda; T. Ogawa; A. S. Yukimatu; A. Kadokura; M. Tsutsumi
Proc. SuperDARN Workshop 2009 in Corsica, Jun. 2009
International conference proceedings, English - Small-scale converging electric field structure in the vicinity of breakup auroral arcs
Hosokawa, K; R. Sugita; A. Kadokura; A. S. Yukimatu; N. Sato; S. E. Milan; M. Lester; G. Bjornsson; T. Saemundsson
Proc. SuperDARN Workshop 2009 in Corsica, Jun. 2009
International conference proceedings, English - Moving mesoscale plasma precipitation in the cusp
S. Taguchi; S. Suzuki; K. Hosokawa; Y. Ogawa; A. S. Yukimatu; N. Sato; M. R. Collier; T. E. Moore
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2009JA014128, Jun. 2009, Peer-reviwed, On 28 March 2001, when the interplanetary magnetic field was strongly duskward, the DMSP F12 spacecraft observed an ion precipitation burst in a latitudinally narrow region near 1200 MLT. A few minutes earlier, the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft, whose field of view (FOV) looks into the high-altitude cusp, detected an enhancement of energetic neutral atom signals, which are produced by the ion injection. The LENA data suggest that the ion injection moved out of its FOV after approximately 4 min. At this time, the ground-based magnetometers of the IMAGE chain in Svalbard, located westward of LENA's FOV, began to indicate perturbations. These perturbations immediately reached a peak and then ceased; the perturbations lasted 2-3 min. During this interval, there was an enhanced westward flow over Svalbard, as observed by the SuperDARN radars. The EISCAT Svalbard radar detected an enhancement of electron density and temperature that was concurrent with this flow enhancement, suggesting that a plasma precipitation burst accompanied with the flow. These observations, which cover a longitudinally extending region of the cusp, strongly suggest the existence of moving mesoscale plasma precipitation (MMPP). The MMPP travels westward with a longitudinally elongated form. Its leading and trailing edges should be created by the temporal effect of the cusp. The other edges, which lie along the streamline, would originate in a spatially limited region along the open-closed line. The boundary of the MMPP form is delineated by both the temporal and spatial structures of the cusp.
Scientific journal, English - Acceleration mechanism of high-speed neutral wind observed in the polar lower thermosphere
T. T. Tsuda; S. Nozawa; S. Oyama; T. Motoba; Y. Ogawa; H. Shinagawa; N. Nishitani; K. Hosokawa; N. Sato; M. Lester; R. Fujii
Journal of Geophysical Research: Space Physics, 114, 4, doi:10.1029/2008JA013867, Apr. 2009, Peer-reviwed, We analyzed data obtained with the European incoherent scatter (EISCAT) Svalbard Radar (ESR) at Longyearbyen (78.2°N, 16.0deg;E in geographic coordinates, 75.2°A in invariant latitude) to advance our understanding of the acceleration mechanism of the lower thermospheric neutral wind when the ionospheric convection becomes enhanced. The Advanced Composition Explorer satellite observed a southward turning in the interplanetary magnetic field at 0843 UT on 16 June 2005. At 0900 UT, the F region ion velocity and the lower thermospheric neutral wind (at 118-km altitude) observed with the ESR began to accelerate significantly in the westward and northwestward directions, respectively. The neutral wind was remarkably accelerated within 1 hour from 0900 UT, and its speed became a value of ∼500 m s-1 at 1000 UT. The wind speed was significantly higher than a typical wind speed at 118 km. We evaluated the ion drag contribution on the generation of the high-speed neutral wind. Our evaluation verifies that the ion drag force could not generate the high-speed neutral wind within such a short time (∼1 hour). This result implies that the major driving force was the horizontal pressure gradient force induced by the Joule heating. We deduced the contribution of the pressure gradient force based on a quantitative estimation of the Joule-heating-induced pressure gradient from the ESR and the Super Dual Auroral Radar Network data. We concluded that, the pressure gradient force was the most probable force in this event. Copyright 2009 by the American Geophysical Union.
Scientific journal, English - Motion of polar cap patches: A statistical study with all-sky airglow imager at Resolute Bay, Canada
K. Hosokawa; T. Kashimoto; S. Suzuki; K. Shiokawa; Y. Otsuka; T. Ogawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2008JA014020, Apr. 2009, Peer-reviwed, A highly sensitive all-sky airglow imager (part of the Optical Mesosphere Thermosphere Imagers [OMTIs]) has been operating for 3 years at Resolute Bay, Canada (geographic latitude 74.7 degrees N; geomagnetic latitude 82.9 degrees N) since January 2005. One of its major applications is the observation of polar cap patches. Polar cap patches are generated in the vicinity of the cusp during southward interplanetary magnetic field (IMF) conditions, and they exhibit dynamic movement, possibly in association with the changes in the IMF orientation. In order to determine how their motions are controlled by the upstream IMF conditions, we applied a motion-tracking algorithm that was based on two-dimensional cross-correlation analysis to consecutive images obtained from January 2005 to December 2007 by the all-sky airglow imager at Resolute Bay. We identified and extracted 561 individual patches and then carried out a statistical study of their motion. It is demonstrated that the speed of patches is primarily controlled by the IMF B(z). Furthermore, the dawn-dusk component of the patch drift velocities is well correlated with the IMF B(y), which is in good agreement with the published By dependence of the nightside polar cap convection. This enables us to monitor the plasma convection within the polar cap by using polar cap patches as tracers.
Scientific journal, English - Unusually elongated, bright airglow plume in the polar cap F region: Is it a tongue of ionization?
K. Hosokawa; T. Tsugawa; K. Shiokawa; Y. Otsuka; T. Ogawa; M. R. Hairston
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 36, doi:10.1029/2009GL037512, Apr. 2009, Peer-reviwed, We report an event of unusually elongated, bright airglow plume, which is considered as an optical manifestation of tongue of ionization (TOI) in the central polar cap. This optical structure was detected with an all-sky airglow imager at Resolute Bay (74.73 degrees N, 265.07 degrees E) during a large magnetic storm on December 15, 2006. The absolute optical intensity of the plume was approximate to 1 kR, which is much brighter than that of non-stormtime polar cap patches. Two-dimensional imaging capability of the all-sky imager demonstrates that some meso-scale structures (approximate to 250-600 km) were embedded within the plume. Simultaneous ion density and drift measurements with the DMSP spacecraft strongly suggest that the plume was extending from the dayside as a narrow stream of dense plasma and thus is an optical manifestation of polar cap TOI. The DMSP data also implies that the possible source of the plume is a narrow stream of storm enhanced density (SED) transported from lower latitudes. The DMSP auroral particle observation demonstrates that the polar cap extremely expanded equatorward during this interval. This extreme expansion allowed the anti-sunward convection to capture plasmas within the SED and deliver them deep into the polar cap as a luminous airglow plume. This observation claims that the plasma transport from the dayside lower latitudes plays an important role in controlling the plasma environment in the polar cap ionosphere during magnetic storms. Citation: Hosokawa, K., T. Tsugawa, K. Shiokawa, Y. Otsuka, T. Ogawa, and M. R. Hairston (2009), Unusually elongated, bright airglow plume in the polar cap F region: Is it a tongue of ionization?, Geophys. Res. Lett., 36, L07103, doi:10.1029/2009GL037512.
Scientific journal, English - Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities
T. Ogawa; N. Nishitani; Y. Otsuka; K. Shiokawa; T. Tsugawa; K. Hosokawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 114, 3, 01 Mar. 2009, Peer-reviwed, We present midlatitude medium-scale traveling ionospheric disturbances (MSTIDs) observed with a Super Dual Auroral Radar Network (SuperDARN) HF radar at around 10 MHz in Hokkaido, Japan, in combination with a 630-nm all-sky imager and a GPS network (GEONET) that provides total electron content (TEC) data. MSTIDs propagating southward from high latitudes are detected at first with the HF radar and then with the imager and GEONET. We analyze two MSTID events, one in winter (event 1) and the other in summer (event 2), to find that MSTIDs appear simultaneously, at least, at 55°-25°N. It is shown that nighttime MSTIDs propagate toward the southwest over a horizontal distance of about 4000 km, and daytime MSTIDs do so toward the southeast. Daytime radar echoes are due to ground/sea surface (GS) scatter, while nighttime echoes in event 1 return from 15-m-scale F region field-aligned irregularities (FAIs) and those in event 2 are due to GS scatter. Doppler velocities of the nighttime F region FAI echoes in event 1 are negative (motion away from the radar) within strong echo regions and are positive (motion toward the radar) within weak echo regions. This fact suggests that the strong (weak) echoes return from suppressed (enhanced) airglow/TEC areas, in line with previous observations over central Japan. The nighttime MSTIDs in events 1 and 2 are often accompanied by concurrent coherent echoes from FAIs in sporadic E (Es) layers. The Es echo areas in event 2 rather coincide with suppressed airglow/TEC areas in the F region that are connected with the echo areas along the geomagnetic field, indicating the existence of E and F region coupling at night. Copyright 2009 by the American Geophysical Union.
Scientific journal, English - Relationship between polar cap patches and field-aligned irregularities as observed with an all-sky airglow imager at Resolute Bay and the PolarDARN radar at Rankin Inlet
K. Hosokawa; K. Shiokawa; Y. Otsuka; T. Ogawa; J. -P. St-Maurice; G. J. Sofko; D. A. Andre
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2008JA013707, Mar. 2009, Peer-reviwed, Simultaneous two-dimensional observations of airglow enhancement and radar backscatter from field-aligned irregularities (FAIs) associated with polar cap patches were conducted. The spatial structure of 630 nm airglow from polar cap patches was imaged using an all-sky airglow imager at Resolute Bay, Canada, while backscatter echoes from decameter-scale FAIs were observed using the newly constructed HF Polar Dual Auroral Radar Network (PolarDARN) radar at Rankin Inlet, Canada. Both the airglow enhancement and the radar backscatter appeared within a structured region with the spatial extent of about 500-1000 km. The decameter-scale FAIs were found to extend over the entire region of airglow enhancement associated with polar cap patches, indicating that the polar patch plasma became almost fully structured soon after initiation (within approximately 20-25 min). These findings imply that some rapid structuring process of the entire patch area is involved in addition to the primary gradient-drift instabilities.
Scientific journal, English - Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities
T. Ogawa; N. Nishitani; Y. Otsuka; K. Shiokawa; T. Tsugawa; K. Hosokawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2008JA013893, Mar. 2009, Peer-reviwed, We present midlatitude medium-scale traveling ionospheric disturbances (MSTIDs) observed with a Super Dual Auroral Radar Network (SuperDARN) HF radar at around 10 MHz in Hokkaido, Japan, in combination with a 630-nm all-sky imager and a GPS network (GEONET) that provides total electron content (TEC) data. MSTIDs propagating southward from high latitudes are detected at first with the HF radar and then with the imager and GEONET. We analyze two MSTID events, one in winter (event 1) and the other in summer (event 2), to find that MSTIDs appear simultaneously, at least, at 55 degrees-25 degrees N. It is shown that nighttime MSTIDs propagate toward the southwest over a horizontal distance of about 4000 km, and daytime MSTIDs do so toward the southeast. Daytime radar echoes are due to ground/sea surface (GS) scatter, while nighttime echoes in event 1 return from 15-m-scale F region field-aligned irregularities (FAIs) and those in event 2 are due to GS scatter. Doppler velocities of the nighttime F region FAI echoes in event 1 are negative (motion away from the radar) within strong echo regions and are positive (motion toward the radar) within weak echo regions. This fact suggests that the strong (weak) echoes return from suppressed (enhanced) airglow/TEC areas, in line with previous observations over central Japan. The nighttime MSTIDs in events 1 and 2 are often accompanied by concurrent coherent echoes from FAIs in sporadic E (E(s)) layers. The E(s) echo areas in event 2 rather coincide with suppressed airglow/TEC areas in the F region that are connected with the echo areas along the geomagnetic field, indicating the existence of E and F region coupling at night.
Scientific journal, English - HF radar polar patch and its relation with the cusp during By -dominated IMF: Simultaneous observations at two altitudes
S. Taguchi; K. Hosokawa; A. Nakao; M. R. Collier; T. E. Moore; N. Sato; A. S. Yukimatu
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 114, 2, 01 Feb. 2009, Peer-reviwed, Recent studies have shown that the motion of the cusp can be deduced from the energetic neutral atom signals detected in the magnetosphere by the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft. We use this approach to understand the characteristics of the formation of a polar patch seen in the dayside ionosphere. During a period of the 28 March 2001 LENA cusp signal event, the SuperDARN radars at Syowa East, Syowa South, and Kerguelen Island identified large-scale features of a polar patch. A region of high backscatter power observed by the radars separates into two parts around 77°, and its high-latitude part moves in the poleward and duskward direction. The separation latitude is about 5° higher than the equatorward boundary of the cusp, which is deduced from the LENA cusp signal. We interpret these observations, including features obtained with other SuperDARN radars in the northern hemisphere, as being due to the IMF By-controlled zonal jet flow that occurred during a period of increase in |By|Bz|, without requiring the change in By polarity that has been often invoked in previous studies. The sharp equatorward boundary of the radar signatures of the polar patch would be an interface between the preexisting flow generally in the antisunward direction and the enhanced zonal flow. The flow enhancement appears to be a fundamental process that forms the large-scale polar patch at latitudes several degrees higher than the cusp. © 2009.
Scientific journal, English - HF radar polar patch and its relation with the cusp during B-Y-dominated IMF: Simultaneous observations at two altitudes
S. Taguchi; K. Hosokawa; A. Nakao; M. R. Collier; T. E. Moore; N. Sato; A. S. Yukimatu
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2008JA013624, Feb. 2009, Peer-reviwed, Recent studies have shown that the motion of the cusp can be deduced from the energetic neutral atom signals detected in the magnetosphere by the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft. We use this approach to understand the characteristics of the formation of a polar patch seen in the dayside ionosphere. During a period of the 28 March 2001 LENA cusp signal event, the SuperDARN radars at Syowa East, Syowa South, and Kerguelen Island identified large-scale features of a polar patch. A region of high backscatter power observed by the radars separates into two parts around 77 degrees, and its high-latitude part moves in the poleward and duskward direction. The separation latitude is about 5 degrees higher than the equatorward boundary of the cusp, which is deduced from the LENA cusp signal. We interpret these observations, including features obtained with other SuperDARN radars in the northern hemisphere, as being due to the IMF B-Y-controlled zonal jet flow that occurred during a period of increase in vertical bar B-Y/B-Z vertical bar, without requiring the change in B-Y polarity that has been often invoked in previous studies. The sharp equatorward boundary of the radar signatures of the polar patch would be an interface between the preexisting flow generally in the antisunward direction and the enhanced zonal flow. The flow enhancement appears to be a fundamental process that forms the large-scale polar patch at latitudes several degrees higher than the cusp.
Scientific journal, English - The Optical Mesosphere Thermosphere Imagers (OMTIs) for network measurements of aurora and airglow
K. Shiokawa; K. Hosokawa; K. Sakaguchi; A. Ieda; Y. Otsuka; T. Ogawa; M. Connors
FUTURE PERSPECTIVES OF SPACE PLASMA AND PARTICLE INSTRUMENTATION AND INTERNATIONAL COLLABORATIONS, AMER INST PHYSICS, 1144, 212-+, 2009, Peer-reviwed, The Optical Mesosphere Thermosphere Imagers (OMTIs) currently consist of eight all-sky cooled-CCD imagers and several interferometers and spectrometers. They are making routine observations of aurora and airglow in Japan, Australia, Indonesia, and Canada. Here we show recent results of OMTIs particularly from. the two Canadian stations at Resolute Bay (RSB) and Athabasca (ATH). At RSB, we observe polar-cap plasma patches almost always during southward IMF periods. From two-dimensional cross-correlation analyses, we determine velocity vectors of the patches, which indicates the ionospheric convection vector, showing high correlation with the IMF-By and -Bz variations. At ATH, we often observe isolated proton arcs and Stable Auroral Red (SAR) arcs, which are located equatorward of the auroral oval. The appearance of the isolated proton arcs is highly correlated with the Pc I geomagnetic pulsations measured simultaneously at ATH, suggesting interactions between the electromagnetic ion cyclotron (EMIC) waves and protons in the vicinity of the plasmapause and the ring current. Similar interactions without waves are also suggested for the SAR arcs, which appear after the substorm expansion phase even without geomagnetic storms. These observations show promising capability to monitor magnetospheric processes from the ground stations, which would contribute to the future satellite projects, such as THEMIS, ERG, and Scope/Xscale.
International conference proceedings, English - Dynamical property of storm time subauroral rapid flows as a manifestation of complex structures of the plasma pressure in the inner magnetosphere
Y. Ebihara; N. Nishitani; T. Kikuchi; T. Ogawa; K. Hosokawa; M. C. Fok; M. F. Thomsen
Journal of Geophysical Research: Space Physics, 114, Jan. 2009, During the intense magnetic storm of 15 December 2006, the midlatitude Super Dual Auroral Radar Network (SuperDARN) Hokkaido radar observed a dynamical character of rapid, westward flows at 50-56 magnetic latitude. The simulation that couples the inner magnetosphere and the subauroral ionosphere was performed using a realistic boundary condition of the hot ion distribution determined from four Los Alamos National Laboratory satellites at 6.6 R E . The following results are obtained using the simulation: (1) In general, morphology of the azimuthal component of the simulated ionospheric plasma flow is consistent with that known as the subauroral polarization stream (SAPS), (2) an increase in the hot ion density in the plasma sheet results in the temporal reduction and subsequent intensification of the rapid flow at certain subauroral latitudes with a delay of ∼40 min, and (3) influence of the plasma sheet temperature on the rapid flow is not evident. The simulated line-of-sight velocity is compared with that obtained by the SuperDARN Hokkaido radar. Agreement between them is found in terms of the temporal and spatial variations of the rapid flows as well as the flow velocity. It is suggested that the dynamical character of the subauroral plasma flow is a direct manifestation of the plasma pressure distribution in the inner magnetosphere (the ring current) especially during the magnetic storm. Copyright 2009 by the American Geophysical Union. - Dynamical property of SAPS as a manifestation of fine structures of the ring current during the magnetic storm of 15 December 2006
Ebihara, Y; N Nishitani; T. Kikuchi; T. Ogawa; K. Hosokawa; M.-C. Fok; M. F. Thomsen
Journal of Geophysical Reseach, 114, doi:10.1029/2008JA013614, 2009, Peer-reviwed
Scientific journal, English - Statistical characteristics of polar cap mesospheric gravity waves observed by an all-sky airglow imager at Resolute Bay, Canada
S. Suzuki; K. Shiokawa; K. Hosokawa; K. Nakamura; W. K. Hocking
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 114, doi:10.1029/2008JA013652, Jan. 2009, Peer-reviwed, An airglow imager at Resolute Bay, Canada (74.7 degrees N, 265.1 degrees E) has been used for the observation of gravity waves in the polar cap mesosphere since January 2005. On the basis of the long-term imaging observations obtained over 137 nights during the winter seasons of 2005 and 2006, we extracted 143 events of small-scale (< 100 km) gravity waves from sequential sodium airglow (589.3 nm) images. The observed waves typically had horizontal wavelengths of 20-50 km and phase speeds of 30-60 ms(-1). The propagation directions were predominantly westward. We also identified larger-scale (> 100 km) gravity waves using airglow keograms, which represent a time series of the horizontal cross sections of the airglow images. The horizontal wavelengths and phase speeds of the large-scale waves were typically 100-400 km and 60-100 ms(-1), respectively. The propagation directions of these large-scale waves also showed a westward preference. The wave parameters appeared to have no relation with the geomagnetic activities represented by the K-p index. On the other hand, the propagation directions of the observed waves were consistent with the prevailing eastward winds in the mesosphere and the updraft associated with a low-pressure area that generally appears to the east of Resolute Bay at tropospheric altitudes. These results suggest that the main source of the gravity waves in the polar cap mesosphere is tropospheric dynamics rather than auroral activities.
Scientific journal, English - SuperDARN Hokkaido radar observation of westward flow enhancement in subauroral latitudes
R. Kataoka; K. Hosokawa; N. Nishitani; Y. Miyoshi
Annales Geophysicae, 27, 4, 1695-1699, 2009, Peer-reviwed, Westward flow enhancement in subauroral latitudes is investigated based on the first one and a half year observation of the SuperDARN Hokkaido radar. A total of 15 events are identified with the criteria of westward flow speed of >
1.0 km/s in magnetic latitude from 45 to 65 deg during geomagnetically disturbed period of Kp>
3+ at 20 magnetic local time. It is found that especially during the storm recovery phase, the flow enhancement occurs in broad range ofDst amplitude, and the occurrence latitude depends on the amplitude of Dst . It is also found that the disturbed K p condition is not sufficient for the appearance of the subauroral flow enhancement as seen by Hokkaido radar while storm-like Dst condition is necessary, supporting the idea that ring current particles play an essential role to enhance the westward flow in subauroral latitudes via magnetosphere-ionosphere coupling through the field-aligned current.
Scientific journal, English - Response of large-scale ionospheric convection to substorm expansion onsets: A case study
Y. Miyashita; K. Hosokawa; T. Hori; Y. Kamide; A. S. Yukimatu; M. Fujimoto; T. Mukai; S. Machida; N. Sato; Y. Saito; I. Shinohara; J. B. Sigwarth
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 113, A12, doi:10.1029/2008JA013586, Dec. 2008, Peer-reviwed, We have studied the response of large-scale ionospheric convection to substorm expansion onsets on the basis of two weak substorms of 1 May 2001, during which a large part of the dawn cell of the two-cell ionospheric convection pattern was monitored by the SuperDARN radars. Ionospheric convection began to enhance first in a localized region of the equatorward part of the dawn cell similar to 2 minutes before the expansion onsets of both substorms and then enhanced in the entire dawn cell successively. The enhanced convection persisted throughout their expansion phase, possibly even near the footprint of a plasma sheet region without fast flows observed by Geotail. These observations suggest that ionospheric convection begins to enhance just before substorm expansion onset and then enhances in the entire cell, possibly regardless of the presence of fast earthward flows in the corresponding plasma sheet region of the magnetotail. The global enhancement of ionospheric convection is consistent with that of magnetotail convection, which also begins just before onset.
Scientific journal, English - Electric field modulation behind pulsating aurora
K. Hosokawa; A. Kadokura; N. Sato; S. E. Milan; M. Lester; G. Bjornsson; Th. Saemundsson
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 113, A11, doi:10.1029/2008JA013601, Nov. 2008, Peer-reviwed, We present, for the first time, the modulation of the electric field at ionospheric altitudes possibly associated with an occurrence of pulsating aurora. In November 2005, campaign-based simultaneous measurements of pulsating aurora were conducted in Iceland with an all-sky TV camera (ATV) at Tjornes (66.20 degrees N, 17.12 degrees W) and the SuperDARN radar at Thykkvibaer (63.77 degrees N, 20.54 degrees W). During an interval within the campaign period, pulsating aurora whose frequency was approximately 8 seconds were observed with the ATV in the morning sector. A quasi-periodic oscillation was identified in the line-of-sight Doppler velocity from the radar backscatter colocated with the pulsating aurora. The amplitude of the velocity fluctuation ranged from 50 to 100 m s(-1), which corresponds to an electric field modulation of 4-7 mV m(-1). The period of the electric field fluctuation was the same as that of the optical pulsating aurora. We suggest that the oscillating Doppler velocity is driven by polarization electric fields generated through charge accumulation at the edges of region of enhanced electron density caused by the occurrence of pulsating aurora.
Scientific journal, English - Estimation of magnetopause motion from low-energy neutral atom emission
K. Hosokawa; S. Taguchi; S. Suzuki; M. R. Collier; T. E. Moore; M. F. Thomsen
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 113, 10, 01 Oct. 2008, Peer-reviwed, A new method for deriving the position of the dayside equatorial magnetopause directly from the measured intensity of energetic neutral atom (ENA) emissions is presented. This approach makes it possible to track the position of the magnetopause using data observed by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. The model is applied to data recorded during a period of high solar wind dynamic pressure on 13 April 2001. In this interval, significant ENA flux was observed originating from the dayside low-latitude magnetosheath. This ENA flux is primarily the result of enhanced charge exchange between the increased solar wind plasma and exospheric hydrogen neutrals. The temporal variation in the estimated magnetopause position is compared with in situ measurements of magnetopause crossings by the LANL-OlA spacecraft in geosynchronous orbit and the results of a recent empirical magnetopause model. It is demonstrated that the subsolar distance of the magnetopause was successfully tracked for a period of more than 1 h. In this particular case example, the dayside magnetopause is closer to the Earth and fluctuates on a shorter timescale than predicted by the previous empirical model based on in situ data. It is also revealed that the subsolar magnetopause can move with speeds of 100-200 km s-1 in response to marked dynamic pressure changes, and during periods of stable dynamic pressure can fluctuates with speeds of up to 50 km s-1. Copyright 2008 by the American Geophysical Union.
Scientific journal, English - Estimation of magnetopause motion from low-energy neutral atom emission
K. Hosokawa; S. Taguchi; S. Suzuki; M. R. Collier; T. E. Moore; M. F. Thomsen
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 113, A10, doi:10.1029/2008JA013124, Oct. 2008, Peer-reviwed, A new method for deriving the position of the dayside equatorial magnetopause directly from the measured intensity of energetic neutral atom (ENA) emissions is presented. This approach makes it possible to track the position of the magnetopause using data observed by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. The model is applied to data recorded during a period of high solar wind dynamic pressure on 13 April 2001. In this interval, significant ENA flux was observed originating from the dayside low-latitude magnetosheath. This ENA flux is primarily the result of enhanced charge exchange between the increased solar wind plasma and exospheric hydrogen neutrals. The temporal variation in the estimated magnetopause position is compared with in situ measurements of magnetopause crossings by the LANL-01A spacecraft in geosynchronous orbit and the results of a recent empirical magnetopause model. It is demonstrated that the subsolar distance of the magnetopause was successfully tracked for a period of more than 1 h. In this particular case example, the dayside magnetopause is closer to the Earth and fluctuates on a shorter timescale than predicted by the previous empirical model based on in situ data. It is also revealed that the subsolar magnetopause can move with speeds of 100-200 km s(-1) in response to marked dynamic pressure changes, and during periods of stable dynamic pressure can fluctuates with speeds of up to 50 km s(-1).
Scientific journal, English - SuperDARN observations of daytime MSTIDs in the auroral and mid-latitudes: Possibility of long-distance propagation
T. Ishida; K. Hosokawa; T. Shibata; S. Suzuki; N. Nishitani; T. Ogawa
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 35, 13, doi:10.1029/2008GL034623, Jul. 2008, Peer-reviwed, The propagation parameters of daytime medium-scale traveling ionospheric disturbances (MSTIDs) are investigated for the first time using near-simultaneous SuperDARN radar data obtained at auroral and middle latitudes. The observations suggest that MSTIDs can propagate from auroral to mid-latitudes with persistent propagation parameters if the dominant propagation direction is approximately equatorward. However, statistical analysis implies that a portion of MSTIDs with higher horizontal phase velocity are unable to reach the mid-latitude due to enhanced dissipation and the reduction of the ion-drag effect.
Scientific journal, English - Conjugate observations of ENA signals in the high-altitude cusp and proton auroral spot in the low-altitude cusp with IMAGE spacecraft
S. Suzuki; S. Taguchi; K. Hosokawa; M. R. Collier; T. E. Moore; H. U. Frey; S. B. Mende
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 35, 13, doi:10.1029/2008GL034543, Jul. 2008, Peer-reviwed, On 28 April 2001, significant enhancements of neutral atom signals were detected in the direction of a high-altitude cusp by the Low-Energy Neutral Atom (LENA) imager onboard the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE). Simultaneously, proton auroral emission was observed in the low-altitude cusp by the Far-Ultraviolet Instrument (FUV) on the IMAGE spacecraft. The temporal variations of their intensities showed a good correlation, suggesting they had a common source. During a brief period, the proton auroral spot moved antisunward and dawnward in conjunction with the motion of the ionospheric footprint of the LENA cusp signal. The Tsyganenko-96 model shows that the possible source location of the LENA cusp signals maps to the FUV spot. Considering the solar wind variations, we have attributed this "moving proton auroral spot'' to a moving flux tube that was created by transient reconnection on the dayside magnetopause and contained relatively high proton densities.
Scientific journal, English - Two-dimensional observations of overshielding during a magnetic storm by the Super Dual Auroral Radar Network (SuperDARN) Hokkaido radar
Y. Ebihara; N. Nishitani; T. Kikuchi; T. Ogawa; K. Hosokawa; M. -C. Fok
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 113, A1, doi:10.1029/2007JA012641, Jan. 2008, Peer-reviwed, [1] Two-dimensional observations of ionospheric plasma flows possibly caused by overshielding are reported for the first time. The observations were made by the midlatitude Super Dual Auroral Radar Network Hokkaido radar in Japan during a major magnetic storm on 15 December 2006. The magnetosphere was exposed continuously to a southward interplanetary magnetic field (IMF) for several hours during the main phase of the storm. Immediately following the subsequent northward turning of the IMF, an antisunward plasma flow was observed for about 14 min in the predusk sector at magnetic latitudes of 50 degrees-60 degrees, reaching a maximum line-of-sight speed of 70-80 m/s. These features are consistent with a simulation of coupling between the ring current and the ionosphere associated with an overshielding condition. Within 1 h of the first observation, a similar antisunward flow was observed during a period of southward oriented IMF. However, the simulation cannot account for the antisunward flow in this case. It is suggested that the shielding/overshielding condition is not simply caused by the northward turning of IMF. This second overshielding-like condition is attributable to a sudden contraction of the polar cap associated with the substorm or to a sudden strengthening of the inertial current converted from the abrupt injection of magnetospheric ions. However, neither fully accounts for the observations.
Scientific journal, English - D region HF radar echoes associated with energetic particle precipitation and pulsating aurora
S. E. Milan; K. Hosokawa; M. Lester; N. Sato; H. Yamagishi; F. Honary
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 26, 7, 1897-1904, 2008, Peer-reviwed, Milan et al. (2001) identified a class of narrow, slow-moving HF radar backscatter echoes which originate between altitudes of 80 and 100 km, the ionospheric D- and lower E-regions. These echoes appeared to be associated with the occurrence of pulsating aurora, which are known to be created by energetic electrons capable of penetrating to D region altitudes. In this study we show that these echoes are observed in tandem with enhancements in cosmic noise absorption (auroral absorption), additional evidence that energetic (>30 keV) particle precipitation is responsible for generating the irregularities from which a radar can scatter. In addition, we show that the D region backscatter echoes occur predominantly in the post-midnight sector during substorm recovery phase, in common with auroral absorption events and pulsating aurora.
Scientific journal, English - Rankin Inlet PolarDARN radar observations of duskward moving Sun-aligned optical forms
A. Koustov; K. Hosokawa; N. Nishitani; T. Ogawa; K. Shiokawa
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 26, 9, 2711-2723, 2008, Peer-reviwed, On 15 February 2007, several duskward moving sun-aligned (SA) auroral forms have been observed by the all-sky camera at Resolute Bay, Nunavut (Canada). Concurrent observations with the Rankin Inlet (RANK) PolarDARN HF radar within the field-of-view of the camera showed signatures of moving auroral forms in all signal parameters with the most remarkable effects being the echo power drop and velocity reversal as the arc reached a specific radar beam/gate. Spatial and temporal variations of the velocity in the vicinity of the SA form are investigated. It is shown that the form-associated convection reversal was located poleward (duskward) of the global-scale convection reversal associated with the dawn cell of the large-scale convection pattern. Thus, the RANK radar was monitoring the polar cap portion of the global-scale convection pattern and its transition from the IMF B-y<0 to the B-y>0 situation. Magnetic perturbations associated with the SA form passing the zenith of several magnetometers are investigated. It is shown that although magnetometer signatures of the moving form were clear, the convection pattern derivation from magnetometer records alone is not straightforward.
Scientific journal, English - Correlative variations of the neutral atom emission in the high-altitude cusp and the fast anti-sunward convection in the low-altitude cusp
Y. Murata; S. Taguchi; K. Hosokawa; A. Nakao; M. R. Collier; T. E. Moore; N. Sato; H. Yamagishi; A. S. Yukimatu
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 112, 11, 01 Nov. 2007, Peer-reviwed, Recent studies have shown that the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft in the magnetosphere detects neutral atoms coming from the direction of the high-altitude cusp. The primary source of the neutral atoms has been reported to be the entry of the ions in the cusp, but the evidence for this remains limited. Therefore we herein report the correlative variations of the neutral atom signal in the direction of the high-altitude cusp and the fast anti-sunward convection in the ionospheric cusp from an event of simultaneous observations from IMAGE/LENA and SuperDARN radar. During a period of IMF B z of -40 to -10 nT on 11 April 2001, LENA on IMAGE at (Z GSM, YGSM, ZGSM) ∼ (4 RE, 0 RE, 4 RE) observed significant enhancements of neutral atom signals in the direction of the high-altitude cusp. In concurrence with these enhancements, SuperDARN radars observed an increase in anti-sunward flow accompanied by equatorward shift of the polar cap boundary. Detailed analyses of the SuperDARN velocity data reveal that the fast anti-sunward flow region widens and shrinks longitudinally in correlation with the increase and decrease of the LENA signal, respectively. This correlation shows that the neutral atom emission in the direction of the high-altitude cusp for southward IMF is due to the ion entry caused by enhanced reconnection on the dayside magnetopause. Hence the present study provides evidence of the cusp ion injection being the primary source of the LENA high-altitude cusp signal for the southward IMF. Copyright 2007 by the American Geophysical Union.
Scientific journal, English - Correlative variations of the neutral atom emission in the high-altitude cusp and the fast anti-sunward convection in the low-altitude cusp
Y. Murata; S. Taguchi; K. Hosokawa; A. Nakao; M. R. Collier; T. E. Moore; N. Sato; H. Yamagishi; A. S. Yukimatu
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 112, A11, doi:10.1029/2007JA012404, Nov. 2007, Peer-reviwed, [1] Recent studies have shown that the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft in the magnetosphere detects neutral atoms coming from the direction of the high-altitude cusp. The primary source of the neutral atoms has been reported to be the entry of the ions in the cusp, but the evidence for this remains limited. Therefore we herein report the correlative variations of the neutral atom signal in the direction of the high-altitude cusp and the fast anti-sunward convection in the ionospheric cusp from an event of simultaneous observations from IMAGE/LENA and SuperDARN radar. During a period of IMF B-Z of -40 to -10 nT on 11 April 2001, LENA on IMAGE at (X-GSM, Y-GSM, Z(GSM)) similar to (4 R-E, 0 R-E, 4 R-E) observed significant enhancements of neutral atom signals in the direction of the high-altitude cusp. In concurrence with these enhancements, SuperDARN radars observed an increase in anti-sunward flow accompanied by equatorward shift of the polar cap boundary. Detailed analyses of the SuperDARN velocity data reveal that the fast anti- sunward flow region widens and shrinks longitudinally in correlation with the increase and decrease of the LENA signal, respectively. This correlation shows that the neutral atom emission in the direction of the high-altitude cusp for southward IMF is due to the ion entry caused by enhanced reconnection on the dayside magnetopause. Hence the present study provides evidence of the cusp ion injection being the primary source of the LENA high-altitude cusp signal for the southward IMF.
Scientific journal, English - Dynamic variations of a convection flow reversal in the subauroral postmidnight sector as seen by the SuperDARN Hokkaido HF radar
Ryuho Kataoka; Nozomu Nishitani; Yusuke Ebihara; Keisuke Hosokawa; Tadahiko Ogawa; Takashi Kikuchi; Yoshizumi Miyoshi
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 34, 21, doi:10.1029/2007GL031552, Nov. 2007, Peer-reviwed, The SuperDARN Hokkaido HF radar, capable of measuring the subauroral ionospheric plasma convection especially during storms, has been in continuous operation since the beginning of December 2006. We report the first two- dimensional observation of a dynamic variation of convection flow reversal in subauroral postmidnight sector during the storm main phase on 29 January 2007. The flow reversal region is extended over 20 degrees in longitude and 5 degrees in latitude, lasting for about 10 - 15 min, and the maximum flow speed is about 0.5 - 1.0 km/ s. The flow reversal structure is reasonably reproduced by the ring current simulation coupled with the ionosphere, suggesting that it is produced by the region 2 field- aligned current associated with the ring current enhancement during the storm main phase. The dynamic variation of the flow reversal structure is interpreted as a transient eastward extension of the elongated dusk convection cell to the postmidnight and equatorward of the dawn cell, associated with the variation of the ring current whose structure is controlled by the interplanetary magnetic field and solar wind dynamic pressure. It is suggested that the ring current variation is highly coupled with the interplanetary parameters and is much more complicated than ever thought.
Scientific journal, English - Storm phase dependence of ion outflow: Statistical signatures obtained by IMAGE/LENA
T. Kunori; M. Nose; S. Taguchi; K. Hosokawa; M. R. Collier; T. E. Moore
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 34, 18, doi:10.1029/2007GL029877, Sep. 2007, Peer-reviwed, The low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) spacecraft can observe energetic neutral atoms (ENA) of 10 eV to a few keV generated by upflowing ions through charge exchange with the Earth's exosphere. Using IMAGE/LENA data, we statistically analyzed behaviors of the ion outflow in the main and recovery phases of the magnetic storms from June 2000 to December 2001. Results show that during the main phase, most of ENA emissions from the Earth's direction are accompanied by the solar wind dynamic pressure (P-dy) enhancements. For the recovery phase, there are no such tendencies. Instead, the ENA flux shows large values at the beginning of the recovery phase, and then decreases with the storm recovery. These results suggest that the dominant mechanism responsible for the ion outflow during the magnetic storms can be totally different between the two phases.
Scientific journal, English - Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations
H. Fujiwara; R. Kataoka; M. Suzuki; S. Maeda; S. Nozawa; K. Hosokawa; H. Fukunishi; N. Sato; M. Lester
ANNALES GEOPHYSICAE, COPERNICUS PUBLICATIONS, 25, 11, 2393-2403, 2007, Peer-reviwed, From simultaneous observations of the European incoherent scatter Svalbard radar (ESR) and the Cooperative UK Twin Located Auroral Sounding System (CUTLASS) Finland radar on 9 March 1999, we have derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region. The ESR and CUTLASS radar observations provide the ionospheric parameters with fine time-resolutions of a few minutes. Although the geomagnetic activity was rather moderate (Kp=3(+)similar to 4), the electric field obtained from the ESR data sometimes shows values exceeding 40 mV/m. The estimated passive energy deposition rates are also larger than 150 W/kg in the upper thermosphere over the ESR site during the period of the enhanced electric field. In addition, enhancements of the Pedersen conductivity also contribute to heating the upper thermosphere, while there is only a small contribution for thermospheric heating from the direct particle heating due to soft particle precipitation in the dayside polar cap/cusp region. In the same period, the CUTLASS observations of the ion drift show the signature of poleward moving pulsed ionospheric flows with a recurrence rate of about 10-20 min. The estimated electromagnetic energy deposition rate shows the existence of the strong heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events.
Scientific journal, English - Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada
K. Hosokawa; K. Shiokawa; Y. Otsuka; A. Nakajima; T. Ogawa; J. D. Kelly
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 33, 15, doi:10.1029/2006GL026916, Aug. 2006, Peer-reviwed, Highly sensitive all-sky airglow imager has been operative at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E; AACGM latitude 82.9 degrees) since January 2005. We present, as a first result from the imager, an event of polar cap patches drifting anti-sunward during the southward IMF conditions. Magnitude and direction of patch drift velocities are computed with a temporal resolution of 2 min by using the newly developed patch-tracking algorithm based on 2D cross correlation analysis. It is well visualized that the patches change their moving speed and direction drastically in a short time scale ( a few minutes). Speed of the patch is primally controlled by the IMF Bz. Dawn-dusk component of the patch drift velocities is well correlated with the IMF By in agreement with published By dependence of the nightside polar cap convection. However, response of the patch drift direction to the IMF By is found to be much slower ( approximate to 20 min) than that of the drift speed to the IMF Bz ( almost instantaneous).
Scientific journal, English - Neutral atom emission in the direction of the high-latitude magnetopause for northward IMF: Simultaneous observations from IMAGE spacecraft and SuperDARN radar
S Taguchi; K Hosokawa; A Nakao; MR Collier; TE Moore; A Yamazaki; N Sato; AS Yukimatu
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 33, 3, doi:10.1029/2005GL025020, Feb. 2006, Peer-reviwed, During a northward interplanetary magnetic field on 27 March 2001, the Low Energy Neutral Atom (LENA) imager on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft in the magnetosphere observed an enhanced emission in the direction of the very high-latitude magnetopause. Simultaneous observations from IMAGE/LENA and SuperDARN radar show that the LENA emission appears concurrently with the enhancement of the sunward flow of the reverse convection in the ionosphere. The field line mapping from the magnetosphere to the ionosphere suggests that the source ions for the LENA emission are in the sunward flow region. Although the direction of the emission is relatively stable, its direction changes slightly so that the emission may shift poleward or equatorward. From these observations, we suggest that LENA can monitor the ion entry caused by cusp reconnection and that the reconnection site moves on a timescale of several minutes.
Scientific journal, English - Simultaneous observations of ions of ionospheric orgin over the ionosphere and in the plasma sheet at storm-time substorms
Nosé, M; T. Kunori; Y. Ono; S. Taguchi; K. Hosokawa; T. E. Moore; M. R. Collier; S. P. Christon; E. W. McEntire
Proceedings of the Eighth International Conference on Substorms, 203-208, 2006
International conference proceedings - Neutral atom emission coming from the direction of the high-latitude magnetopause under northward IMF
Taguchi, S; K. Hosokawa; Y. Murata; A. Nakao; M. R. Collier; T. E. Moore; A. Yamazaki; N. Sato; A. S. Yukimatu
Advances in Polar Upper Atmospheric Research, National Institute of Polar Research, 20, 17-26, 2006, Peer-reviwed, The Low Energy Neutral Atom (LENA) imager on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft in the magnetosphere can detect neutral particles coming from the direction of the magnetopause. During a period of dynamic pressure of 〜6 nPa and IMF B_Z of 〜15nT on March 27, 2001, significant neutral atom emissions occurred in the direction of the very high-latitude magnetopause. Simultaneous observations from IMAGE/LENA and SuperDARN radar show that the LENA emission appears concurrently with the enhancement of the sunward flow of the reverse convection in the ionosphere. In a recent paper (S. Taguchi et al., Geophys. Res. Lett., 33, L03101, doi: 10.1029/2005GL025020, 2006) this type of emission has been interpreted as being produced by the fast ion flow caused by cusp reconnection through charge exchange with the Earth's hydrogen exosphere. In other words, remote sensing using LENA imager can be applied in order to determine the stability of the reconnection site. From results of analyses of LENA emission data we show that the reconnection "spot" mapped on a sphere having a radius of 8 R_E shifts tailward by approximately 1 R_E over 10min while fluctuating.
Scientific journal, English - Monitoring the high-altitude cusp with the Low Energy Neutral Atom imager: Simultaneous observations from IMAGE and Polar
S Taguchi; SH Chen; MR Collier; TE Moore; MC Fok; K Hosokawa; A Nakao
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 110, A12, doi:10.1029/2005JA011075, Dec. 2005, Peer-reviwed, [1] The Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft in the dayside magnetosphere can detect neutral particles that are emitted in the magnetosheath flow. During a period of dynamic pressure of 4 - 6 nPa and interplanetary magnetic field (IMF) B-z of - 5 to 3 nT on 12 April 2001, LENA on IMAGE at (X-GSM, Y-GSM, Z(GSM)) similar to (4 R-E, 0 R-E, 6 R-E) observed significant emission in the direction of the high-latitude magnetosheath. Detailed analyses have revealed that the high-latitude sheath emission consists of two parts: the stable emission at the higher latitudes and the lower-latitude emission that occurs on and off. During the interval of this event, the Polar spacecraft was located at somewhat lower latitudes than IMAGE in similar noon meridian, and the plasma observations with the Thermal Ions Dynamic Experiment showed that the entry of the cusp ions happens in concurrence with the appearance of the lower-latitude LENA emission. This coincidence strongly suggests that the cusp ions flowing earthward charge exchange with the hydrogen exosphere. For the higher-latitude emission, its stability suggests that the source is associated with the structure persistently existing, which is consistent with the recent result showing that the sheath flow in the cusp indentation can create neutral atom emissions. Comparison of the LENA emission and ACE solar wind suggests that the lower-latitude LENA emission occurs during the southward tilting of dawnward IMF, indicating that this emission is associated with the earthward ion flux along the newly reconnected field lines. Hence this unique event for the simultaneous observations strongly suggests that LENA monitors the entry of the ions in the cusp, which is triggered by the southward tilting of the IMF, and that the significant flux of the cusp ion entry occurs equatorward of and separately from the cusp indentation.
Scientific journal, English - Overwhelming O+ contribution to the plasma sheet energy density during the October 2003 superstorm: Geotail/EPIC and IMAGE/LENA observations
M Nose; S Taguchi; K Hosokawa; SP Christon; RW McEntire; TE Moore; MR Collier
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 110, A9, doi:10.1029/2004JA010930, Aug. 2005, Peer-reviwed, [1] We studied dynamics of O+ ions during the superstorm that occurred on 29 - 31 October 2003, using energetic (9 - 210 keV/e) ion flux data obtained by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite and neutral atom data in the energy range of 10 eV to a few keV acquired by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite. Since the low-energy neutral atoms are created from the outflowing ionospheric ions by the charge exchange process, we could examine variations of ionospheric ion outflow with the IMAGE/LENA data. In the near-Earth plasma sheet of X-GSM similar to - 6 R-E to - 8.5 R-E, we found that the H+ energy density showed no distinctive differences between the superstorm and quiet intervals ( 1 - 10 keV cm(-3)), while the O+ energy density increased from 0.05 - 3 keV cm(-3) during the quiet intervals to similar to 100 keV cm(-3) during the superstorm. The O+/ H+ energy density ratio reached 10 - 20 near the storm maximum, which is the largest ratio in the near-Earth plasma sheet ever observed by Geotail, indicating more than 90% of O+ in the total energy density. We argued that such extreme increase of the O+/ H+ energy density ratio during the October 2003 superstorm was due to mass-dependent acceleration of ions by storm-time substorms as well as an additional supply of O+ ions from the ionosphere to the plasma sheet. We compared the ion composition between the ring current and the near-Earth plasma sheet reported by previous studies and found that they are rather similar. On the basis of the similarity, we estimated that the ring current had the O+/ H+ energy density ratio as large as 10 - 20 for the October 2003 superstorm.
Scientific journal, English - Extraction of polar mesosphere summer echoes from SuperDARN data
K Hosokawa; T Ogawa; NF Arnold; M Lester; N Sato; AS Yukimatu
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 32, 12, doi:10.1029/2005GL022788, Jun. 2005, Peer-reviwed, An algorithm for automated extraction of polar mesosphere summer echoes (PMSE) from near-range measurements of the Super Dual Auroral Radar Network (SuperDARN) is applied to observations obtained by the Syowa East (69.01 degrees S, 38.61 degrees E) and Iceland East (63.77 degrees N, -20.54 degrees W) radars whose fields-of-view are magnetically conjugate. The rate of PMSE occurrence in the SuperDARN data is greatly enhanced in summer months, reaching a maximum of approximate to 90% in Iceland and 60% in Syowa near the summer solstice. The diurnal variation of PMSE occurrence reaches a maximum near the noon meridian, with a distinct minimum at 20LT. These features are consistent with those derived from previous VHF radar observations, suggesting that the SuperDARN data contain large numbers of PMSE events. The interhemispheric asymmetry of PMSE occurrence is also estimated, and it is shown that the PMSE activity is approximate to 1.5 times higher in the Northern Hemisphere (N.H.) than in the Southern Hemisphere (S.H.). Thus, interhemispheric asymmetry in PMSE occurrence appears to exist, but is much weaker than that predicted previously based on VHF radar observations.
Scientific journal, English - Monitoring the high-altitude cusp with the low energy neutral atom imager: Simultaneous observations from IMAGE and polar
S. Taguchi; S. H. Chen; M. R. Collier; T. E. Moore; M. C. Fok; K. Hosokawa; A. Nakao
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 110, 12, 2005, Peer-reviwed, The Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft in the dayside magnetosphere can detect neutral particles that are emitted in the magnetosheath flow. During a period of dynamic pressure of 4-6 nPa and interplanetary magnetic field (IMF) Bz of -5 to 3 nT on 12 April 2001, LENA on IMAGE at (XGSM, YGSM, ZGSM) ∼ (4 RE, 0 RE, 6 RE) observed significant emission in the direction of the high-latitude magnetosheath. Detailed analyses have revealed that the high-latitude sheath emission consists of two parts: the stable emission at the higher latitudes and the lower-latitude emission that occurs on and off. During the interval of this event, the Polar spacecraft was located at somewhat lower latitudes than IMAGE in similar noon meridian, and the plasma observations with the Thermal Ions Dynamic Experiment showed that the entry of the cusp ions happens in concurrence with the appearance of the lower-latitude LENA emission. This coincidence strongly suggests that the cusp ions flowing earthward charge exchange with the hydrogen exosphere. For the higher-latitude emission, its stability suggests that the source is associated with the structure persistently existing, which is consistent with the recent result showing that the sheath flow in the cusp indentation can create neutral atom emissions. Comparison of the LENA emission and ACE solar wind suggests that the lower-latitude LENA emission occurs during the southward tilting of dawnward IMF, indicating that this emission is associated with the earthward ion flux along the newly reconnected field lines. Hence this unique event for the simultaneous observations strongly suggests that LENA monitors the entry of the ions in the cusp, which is triggered by the southward tilting of the IMF, and that the significant flux of the cusp ion entry occurs equatorward of and separately from the cusp indentation. Copyright 2005 by the American Geophysical Union.
Scientific journal, English - On the relationship between spectral characteristics of high-latitude irregularities and small-scale electromagnetic field fluctuations
Hosokawa, K; S. Yamashita; P. Stauning; A. S. Yukimatu; N. Sato; T. Iyemori
Proc. SuperDARN workshop 2004 in Saskatoon, Canada, May 2004
International conference proceedings, English - Statistical analysis of backscatters from first range gates with SENSU Syowa East and CUTLASS Iceland East - an attenmpt to estimate interhemispheric asymmetry in PMSE activities -
Hosokawa, K; T. Ogawa; N. F. Arnold; M. Lester; A. S. Yukimatu; N. Sato
Proc. SuperDARN workshop 2004 in Saskatoon, Canada, May 2004
International conference proceedings, English - Poleward-moving patch of neutral atoms as observed by the IMAGE spacecraft Low Energy Neutral Atom (LENA) imager - manifestation of transient dayside reconnection? -
Hosokawa, K; S. Taguchi; A. Nakano; M. R. Collier; T. E. Moore; M. Lester; A. S. Yukimatu; N. Sato
Proc. SuperDARN workshop 2004 in Saskatoon, Canada, May 2004
International conference proceedings, English - Origin of the SuperDARN broad Doppler spectra: First observational evidence from Oersted satellite magnetometer
Hosokawa, K; S. Yamashita; P. Stauning; N. Sato; A. S. Yukimatu; T. Iyemori
Annales Geophysicae, 22, doi:10.5194/angeo-22-159-2004, 2004, Peer-reviwed
Scientific journal, English - Origin of the SuperDARN broad Doppler spectra: simultaneous observation with Oersted satellite magnetometer
K. Hosokawa; S. Yamashita; P. Stauning; N. Sato; A. S. Yukimatu; T. Iyemori
Ann. Geophys., 22, 1, 159-168, Jan. 2004, Peer-reviwed, We perform a case study of a favorable conjunction of an overpass of the Oersted satellite with the field-of-view of the SuperDARN Syowa East radar during an interval of the southward IMF Bz. At the time, the radar observed an L-shell aligned boundary in the spectral width around the dayside ionosphere. Simultaneously, high-frequency (0.2–5Hz) magnetic field fluctuations were observed by the Oersted satellite's high-time resolution magnetometer. These magnetic field fluctuations are considered to be Alfvén waves possibly associated with the particle which precipitates into the dayside high-latitude ionosphere when magnetic reconnection occurs. It has been theoretically predicted that the time-varying electric field is the dominant physical process to expand the broad HF radar Doppler spectra. Our observation clearly demonstrates that the boundary between narrow and broad spectral widths is corresponding well to the boundary in the level of the fluctuations, which supports the previous theoretical prediction. A close relationship between electric and magnetic field fluctuations and particle precipitations during southward IMF conditions has been confirmed by many authors. The present observation allows us to suggest that the boundary between narrow and broad Doppler spectral widths observed in the dayside ionosphere is connected with the signature of the open/closed field line boundary, such as the cusp particle precipitations via electric and magnetic field fluctuations for the case of the negative IMF Bz conditions.
Scientific journal, English - Origin of the SuperDARN broad Doppler spectra: simultaneous observation with Oersted satellite magnetometer
K Hosokawa; S Yamashita; P Stauning; N Sato; AS Yukimatu; T Iyemori
ANNALES GEOPHYSICAE, EUROPEAN GEOPHYSICAL SOC, 22, 1, 159-168, 2004, Peer-reviwed, We perform a case study of a favorable conjunction of an overpass of the Oersted satellite with the field-of-view of the SuperDARN Syowa East radar during an interval of the southward IMF B-z At the time, the radar observed an L-shell aligned boundary in the spectral width around the dayside ionosphere. Simultaneously, high-frequency (0.2-5Hz) magnetic field fluctuations were observed by the Oersted satellite's high-time resolution magnetometer. These magnetic field fluctuations are considered to be Alfven waves possibly associated with the particle which precipitates into the dayside high-latitude ionosphere when magnetic reconnection occurs. It has been theoretically predicted that the time-varying electric field is the dominant physical process to expand the broad HF radar Doppler spectra. Our observation clearly demonstrates that the boundary between narrow and broad spectral widths is corresponding well to the boundary in the level of the fluctuations, which supports the previous theoretical prediction. A close relationship between electric and magnetic field fluctuations and particle precipitations during southward IMF conditions has been confirmed by many authors. The present observation allows us to suggest that the boundary between narrow and broad Doppler spectral widths observed in the dayside ionosphere is connected with the signature of the open/closed field line boundary, such as the cusp particle precipitations via electric and magnetic field fluctuations for the case of the negative IMF B-z conditions.
Scientific journal, English - Statistics of antarctic mesospheric echoes observed with the SuperDARN Syowa Radar
K Hosokawa; T Ogawa; AS Yukimatu; N Sato; T Iyemori
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 31, 2, doi:10.1029/2003GL018776, Jan. 2004, Peer-reviwed, An oblique-sounding coherent HF radar of the SuperDARN (Super Dual Auroral Radar Network) at about 11 MHz sometimes receives peculiar backscatter returns, which are suspected as Polar Mesosphere Summer Echoes (PMSE), from ranges very close to the radar site. To disclose their statistical features, we looked for such echoes that were observed, under quiet geomagnetic conditions, during 46 months from 1997 until 2000 with the SuperDARN radar at Syowa Station, Antarctica (69.0degreesS, 38.6degreesE). With some strict criteria for echo selection, we identified 22 events in summer months and 2 events in August and September. Their distinct seasonal variation evidences that these near range echoes in summer months are indeed the Antarctic PMSE. Origin of the two spring echoes is not clear at the moment. The occurrence probability of the summer echoes seems to increase with year. We, however, need more data accumulation to confirm this trend. These results indicate that the SuperDARN radars can be used to routinely monitor the activity of PMSE in a wide area of the polar mesosphere in both hemispheres.
Scientific journal, English - Simultaneous observations of the cusp with IMAGE Low Energy Neutral Atoms Imager and SuperDARN radar
Taguchi, S; K. Hosokawa; M. R. Collier; M.-C. Fok; A. S. Yukimatu; N. Sato; R. A. Greenwald
Advances in Polar Upper Atmospheric Research, 18, 53-64, 2004, Peer-reviwed, The Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft observed significant emission in the high-latitude magnetosheath direction during an extreme solar wind condition on April 11, 2001. The emission was modulated in such a manner that the sources shifted equatorward in the high-latitude sheath while sometimes undergoing brief poleward returns. This modulation and the IMF BZ tend to have correlative variations. During this interval of interest, SuperDARN was receiving strong backscattered signals from large potions of the dayside ionosphere. This observation indicates that the equatorward motion of the cusp latitude consists of rapid and slow phases. This kind of equatorward shift appears to correlate with the motion of the emission observed by LENA in the direction of the high-latitude sheath, which gives evidence for a means for monitoring the high-altitude cusp using IMAGE/LENA. It thus appears that the two remote sensing observations, i.e., IMAGE/LENA and SuperDARN radar would provide promising opportunities to understand the detailed dynamics of the polar cusp extending from the low-altitudes to the high-altitudes.
Scientific journal, English - A numerical simulation of the geomagnetic sudden commencement: 1. Generation of the field-aligned current associated with the preliminary impulse
S Fujita; T Tanaka; T Kikuchi; K Fujimoto; K Hosokawa; M Itonaga
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 108, A12, doi:10.1029/2002JA009407, Dec. 2003, Peer-reviwed, The magnetospheric response to a solar wind impulse, a geomagnetic sudden commencement, is studied using an MHD model of the coupled solar wind-magnetosphere-ionosphere system. This paper discusses propagation of the first signal launched by the impulse and generation of the field-aligned current that causes the ground magnetic signal detected as the preliminary impulse (PI). It is revealed that the PI current is first excited as an enhanced Chapman-Ferraro current in the magnetopause and next turns to the magnetosphere along the wavefront of the compressional signal launched by the impulse. It is finally converted to a field-aligned current via mode coupling due to plasma nonuniformity. The current in the wavefront region is an inertia current. We present a quantitative model of the PI model presented by Araki [1994] by using a numerical simulation.
Scientific journal, English - Interhemispheric comparison of spectral width boundary as observed by SuperDARN radars
K Hosokawa; EE Woodfield; M Lester; SE Milan; N Sato; AS Yukimatu; T Iyemori
ANNALES GEOPHYSICAE, EUROPEAN GEOPHYSICAL SOC, 21, 7, 1553-1565, Jul. 2003, Peer-reviwed, Previous studies have shown that dayside equatorward edge of coherent HF radar backscatter having broad Doppler spectral width is coincident with the equatorward edge of the cusp particle precipitation. This enables the boundary between broad and narrow spectral width backscatters (spectral width boundary) in the dayside magnetic local time sector to be used as a proxy for the open/closed field line boundary. The present case study employs magnetically conjugate SuperDARN coherent HF radars to make an interhemispheric comparison of the location and variation of the spectral width boundaries. Agreement between the magnetic latitudes of the boundaries in both hemispheres is remarkable. Correlation coefficients between the latitudes of the boundaries are larger than 0.70. Temporal variation of the spectral width boundary follows the same equatorward trend in both hemispheres. This is consistent with the accumulation of open flux in the polar cap by dayside low-latitude magnetopause reconnection, expected when IMF B-z is negative. Boundaries in both hemispheres also exhibit short-lived poleward motions superposed on the general equatorward trend, which follows the onset of substorm expansion phase and a temporary northward excursion of IMF B-z during substorm recovery phase. There is an interhemispheric difference in response time to the substorm occurrence between two hemispheres. The spectral width boundary in the Southern Hemisphere starts to move poleward 10 min earlier than that in the Northern Hemisphere. We discuss this difference in terms of interhemispheric asymmetry of the substorm breakup region in the longitudinal direction associated with the effect of IMF B-y.
Scientific journal, English - Transient production of F-region irregularities associated with TCV passage
R Kataoka; H Fukunishi; K Hosokawa; H Fujiwara; AS Yukimatu; N Sato; YK Tung
ANNALES GEOPHYSICAE, EUROPEAN GEOPHYSICAL SOC, 21, 7, 1531-1541, Jul. 2003, Peer-reviwed, Transient production of F-region plasma irregularities due to traveling convection vortices (TCVs) was investigated using the Super Dual Auroral Radar Network (SuperDARN) combined with ground magnetometer networks and the POLAR ultraviolet imager. We selected two large-amplitude (100-200 nT) TCV events that occurred on 22 May 1996 and 24 July 1996. It is found that the TCV-associated HF backscatter arises in blobs with spatial scale of a few hundreds km. They traveled following tailward bulk motion of the TCV across the three fields-of-view of the SuperDARN HF radars in the prenoon sector. The spectra in the blobs showed unidirectional Doppler velocities of typically 400-600 m/s, with flow directions away from the radar. These unidirectional velocities correspond to the poleward and/or eastward convective flow near the leading edge of upward field-aligned current. The backscatter blobs overlapped the poleward and westward part of the TCV-related transient aurora. It is likely that the transient backscatter blobs are produced by the three-dimensional gradient drift instabilities in the three-dimensional current system of the TCV In this case, nonlinear rapid evolution of irregularities would occur in the upward field-aligned current region. The spectral width of the backscatter blob is typically distributed between 50 and 300 m/s, but sometimes it is over 400 m/s. This suggests that the temporal broad spectra over 400 m/s are produced by Pc1-2 bursts, while the background spectral width of 50-300 m/s are produced by the velocity gradient structure of convection vortices themselves.
Scientific journal, English - Characteristics of polar mesosphere summer echoes observed with the Syowa Station HF radars
Ogawa, T; K. Hosokawa; N. Nishitani; N. Sato; H. Yamagishi; A. S. Yukimatu
Advances in Polar Upper Atmospheric Research, 17, 13-29, 2003, Peer-reviwed, Polar mesosphere summer echoes(PMSE) are strong VHF-UHF radar echoes from the high-latitude cold mesopause at around 80-90km altitudes in summer. Although a number of in situ and radar observations of PMSE have been made until now, generation mechanisms of PMSE and scattering processes of radar waves due to PMSE-associated irregularities are still controversial. In this paper, PMSE detected for the first time in December 1997 and January 1998 with the oblique incidence SuperDARN HF radars at Syowa Station, Antarctica(69.0°S , 39.6°E ), are summarized to reveal the characteristics of PMSE at HF band. They appear at slant ranges of 180-315km with elevation angles of 15°-30° between 1030 and 1230UT or between 2100 and 0140UT, and are characterized by durations of 65-110min with intermittent subsidence and quasi-periodic oscillations of echo power with periods of 5-20min, due to short-period atmospheric gravity waves. Detailed analysis of the December 15, 1997 event reveals the followings: 1) echo power is less than 30dB, Doppler velocity between -40 and +40m/s, and spectral width less than 50m/s, respectively, 2) there exists no particular correlation among power, velocity and width, and 3) PMSE occurrence can be related to eastward neutral wind due to semi-diurnal tide that may induce the decrease in the mesospheric temperature.
Scientific journal, English - Simultaneous measurement of duskside subauroral irregularities from the CUTLASS Finland radar and EISCAT UHF system
K Hosokawa; M Sugino; M Lester; N Sato; AS Yukimatu; T Iyemori
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 107, A12, doi:10.1029/2002JA009494, Dec. 2002, Peer-reviwed, [1] Dusk scatter event (DUSE) (first reported by Ruohoniemi et al. [1988]) is one of the most reproducible features among the SuperDARN radar backscatter within the subauroral ionosphere. Hosokawa et al. [2001] analyzed the scattering occurrence percentage of the Northern Hemisphere SuperDARN radars in a statistical fashion and pointed out that the region where the DUSE appears has a close relationship with the duskside end of the midlatitude trough in longitudinal direction. They proposed a model explaining the generation of the DUSE which employs a Sunward density gradient at the duskside edge of the trough and an ambient poleward electric field. In order to confirm the model proposed by Hosokawa et al. [2001], we have investigated two DUSE events which had been observed by the CUTLASS Finland radar and the EISCAT UHF system simultaneously. Consequently, when the CUTLASS Finland radar observed the DUSE, a Sunward directed density gradient was observed by the EISCAT in the vicinity of the DUSE. After the passage of the DUSE the EISCAT observed an ion temperature enhancement which suggested that the EISCAT entered the trough through its duskside edge. These observational facts suggest that the geometry of the parameters around the DUSE is quite consistent with the model proposed by Hosokawa et al. [2001]. In addition, the EISCAT observed an enhancement of the poleward electric field around the DUSE, and a signature of the substorm was identified by the ground magnetometer on the nightside. We suggest generation mechanisms of the trough responsible for the DUSE during substorm conditions in terms of the role of the enhanced subauroral electric field and discuss a relationship between the DUSE and the other substorm-related phenomena.
Scientific journal, English - An inter-hemispheric, statistical study of nightside spectral width distributions from coherent HF scatter radars
EE Woodfield; K Hosokawa; SE Milan; N Sato; M Lester
ANNALES GEOPHYSICAE, EUROPEAN GEOPHYSICAL SOC, 20, 12, 1921-1934, Dec. 2002, Peer-reviwed, A statistical investigation of the Doppler spectral width parameter routinely observed by HF coherent radars has been conducted between the Northern and Southern Hemispheres for the nightside ionosphere. Data from the SuperDARN radars at Thykkvibaer, Iceland and Syowa East, Antarctica have been employed for this purpose. Both radars frequently observe regions of high (> 200 ms(-1)) spectral width polewards of low (< 200 ms(-1)) spectral width. Three years of data from both radars have been analysed both for the spectral width and line of sight velocity. The pointing direction of these two radars is such that the flow reversal boundary may be estimated from the velocity data, and therefore, we have an estimate of the open/closed field line boundary location for comparison with the high spectral widths. Five key observations regarding the behaviour of the spectral width on the nightside have been made. These are (i) the two radars observe similar characteristics on a statistical basis; (ii) a latitudinal dependence related to magnetic local time is found in both hemispheres; (iii) a seasonal dependence of the spectral width is observed by both radars, which shows a marked absence of latitudinal dependence during the summer months; (iv) in general, the Syowa East spectral width tends to be larger than that from Iceland East, and (v) the highest spectral widths seem to appear on both open and closed field lines. Points (i) and (ii) indicate that the cause of high spectral width is magnetospheric in origin. Point (iii) suggests that either the propagation of the HF radio waves to regions of high spectral width or the generating mechanism(s) for high spectral width is affected by molar illumination or other seasonal effects. Point (iv) suggests that the radar beams from each of the radars are subject either to different instrumental or propagation effects, or different geophysical conditions due to their locations, although we suggest that this result is more likely to be due to geophysical effects. Point (v) leads us to conclude that, in general, the boundary between low and high spectral width will not be a good proxy for the open/closed field line boundary.
Scientific journal, English - Statistical characteristics of Doppler spectral width as observed by the conjugate SuperDARN radars
K Hosokawa; EE Woodfield; M Lester; SE Milan; N Sato; AS Yukimatu; T Iyemori
ANNALES GEOPHYSICAE, EUROPEAN GEOPHYSICAL SOC, 20, 8, 1213-1223, Aug. 2002, Peer-reviwed, We performed a statistical analysis of the occurrence distribution of Doppler spectral width around the day-side high-latitude ionosphere using data from the conjugate radar pair composed of the CUTLASS Iceland-East radar in the Northern Hemisphere and the SENSU Syowa-East radar in the Southern Hemisphere. Three types of spectral width distribution were identified: (1) an exponential-like distribution in the lower magnetic latitudes (below 72), (2) a Gaussian-like distribution around a few degrees magnetic latitude, centered on 78, and (3) another type of distribution in the higher magnetic latitudes (above 80). The first two are considered to represent the geophysical regimes such as the LLBL and the cusp, respectively, because they are similar to the spectral width distributions within the LLBL and the cusp, as classified by Baker et al. (1995). The distribution found above 80 magnetic latitude has been clarified for the first time in this study. This distribution has similarities to the exponential-like distribution in the lower latitude part, although clear differences also exist in their characteristics. These three spectral width distributions are commonly identified in conjugate hemispheres. The latitudinal transition from one distribution to another exhibits basically the same trend between two hemispheres. There is, however, an interhemispheric difference in the form of the distribution around the cusp latitudes, such that spectral width values obtained from Syowa-East are larger than those from Iceland-East. On the basis of the spectral width characteristics, the average locations of the cusp and the open/closed field line boundary are estimated statistically.
Scientific journal, English - SuperDARN HF Radar Signatures of Traveling Convection Vortices
Kataoka, R; H. Fukunishi; A. S. Yukimatu; N. Sato; K. Hosokawa; SuperDARN PIs
Proc. SuperDARN workshop 2002, 2.12.1-2.12.30, May 2002
International conference proceedings, English - Simultaneous measurement of duskside subauroral irregularities from the CUTLASS Finland radar and EISCAT UHF system
K. Hosokawa; M. Sugino; M. Lester; N. Sato; A. S. Yukimatu; T. Iyemori
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 107, 12, 2002, Peer-reviwed, Dusk scatter event (DUSE) (first reported by Ruohoniemi et al. [1988]) is one of the most reproducible features among the SuperDARN radar backscatter within the subauroral ionosphere. Hosokawa et al. [2001] analyzed the scattering occurrence percentage of the Northern Hemisphere SuperDARN radars in a statistical fashion and pointed out that the region where the DUSE appears has a close relationship with the duskside end of the midlatitude trough in longitudinal direction. They proposed a model explaining the generation of the DUSE which employs a Sunward density gradient at the duskside edge of the trough and an ambient poleward electric field. In order to confirm the model proposed by Hosokawa et al. [2001], we have investigated two DUSE events which had been observed by the CUTLASS Finland radar and the EISCAT UHF system simultaneously. Consequently, when the CUTLASS Finland radar observed the DUSE, a Sunward directed density gradient was observed by the EISCAT in the vicinity of the DUSE. After the passage of the DUSE the EISCAT observed an ion temperature enhancement which suggested that the EISCAT entered the trough through its duskside edge. These observational facts suggest that the geometry of the parameters around the DUSE is quite consistent with the model proposed by Hosokawa et al. [2001]. In addition, the EISCAT observed an enhancement of the poleward electric field around the DUSE, and a signature of the substorm was identified by the ground magnetometer on the nightside. We suggest generation mechanisms of the trough responsible for the DUSE during substorm conditions in terms of the role of the enhanced subauroral electric field and discuss a relationship between the DUSE and the other substorm-related phenomena. Copyright 2002 by the American Geophysical Union.
Scientific journal, English - Source of field-aligned irregularities in the subauroral F region as observed by the SuperDARN radars
K Hosokawa; T Iyemori; AS Yukimatu; N Sato
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 106, A11, 24713-24731, Nov. 2001, Peer-reviwed, The HF radars of the Super Dual Auroral Radar Network (SuperDARN) observe the E x B convective drift of ionospheric plasma when suitable small-scale field-aligned irregularities (FAI) from which to scatter are present. In order to estimate the distribution of FAIs in the subauroral F region, we have investigated the scattering occurrence percentage using data from six Northern Hemisphere radars during 39 months between July 1995 and September 1998. We have identified a morphological feature known as the dusk scatter event (DUSE; first reported by Ruohoniemi et al. [1988]) in detail and clarified its relation to the boundaries of the plasma density within the subauroral F region. In all months., the DUSE appears within a few hours local time on the eveningside of sunset, where the magnetic latitude is slightly lower than the equatorward edge of the auroral oval, which corresponds to the density-depleted structure known as the midlatitude trough. There exists a clear UT effect in the characteristics of DUSE, such that DUSE is more pronounced for UTs corresponding to dusk on the prime magnetic meridian (0 degrees geomagnetic longitude). Furthermore, an enhancement of scattering occurrence around sunrise within the trough, which is termed dawn scatter event (DASE), was newly identified. The region where the DUSE or DASE occurs has a close relationship with the, duskside and dawnside ends of the midlatitude trough in the longitudinal direction (which are termed the sunward edges of the trough in this paper), where sunward directed steep plasma density gradients exist. The Kp dependence of the scattering occurrence was also examined. In disturbed conditions, the DUSE appears at earlier local times compared with that in quiet conditions, which is consistent with the Kp dependence of the sunward edge of the trough. Three. models based oil the gradient drift, instability were discussed. It was found that, the model which is based oil the sunward plasma density gradient at the sunward edges of the midlatitude trough and ambient electric field is most favorable for the growth of FAIs in this region and call consistently explain the statistical features of DUSE and DASE. These facts indicate that we can estimate the longitudinal extent of the midlatitude trough from the appearance of DUSE and DASE observed by SuperDARN.
Scientific journal, English - Source of plasma irregularities in the subauroral F region as observed by the SuperDARN radars
Hosokawa, K; T. Iyemori; A. S. Yukimatu; N. Sato; M. Sugino
Proc. 2001 Asia Pacific-Radio Science Conference, p.346, 2001 - Spatial distribution of irregularity occurrence rate in the subauroral F region as observed by the SuperDARN radars
Hosokawa, K; T. Iyemori; A. S. Yukimatu; N. Sato
Proc. CRL "Alaska Project" HF radar Working Group meeting, pp.47-59, 2000 - Characteristics of solar flare effect in the high-latitude ionosphere as observed by the SuperDARN radars
Hosokawa, K; T. Iyemori; A. S. Yukimatu; N. Sato
Advances in Polar Upper Atmosphere Research, 14, 66-75, 2000, Peer-reviwed, Sudden perturbations of the ground magnetic fields at solar flares are called geomagnetic Solar Flare Effect (SFE). An SFE is the extra ionization produced by the X-ray emission from a solar flare. We analyzed 10 intense SFE events from 1996 to 1998 using SuperDARN HF radar network and other instruments located in the northern hemisphere. Two typical ionospheric signatures associated with the solar flares are revealed, one is a sudden fade-out of backscatter echoes, and the other is an appearance or variation of field-aligned irregularities. Sudden fade-out is observed only in the sunlit hemisphere, and the appearance or variation of irregularities are observed only near the terminator. In addition, we investigated one event out of ten in detail and found that there exists a discontinuity of the electric field or conductivity around the irregularity. This fact suggests that the variation of conductivity or electric field in the E region could affect the irregularity formation in the F region.
Scientific journal, English
MISC
- Es層形成過程の中性大気とプラズマ大気の同時観測による解明 S-310-46号機プロジェクト—Elucidation of the generation process of sporadic E layers by simultaneous observation of the neutral and ionized atmospheres: S-310-46 rocket project
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第5回観測ロケットシンポジウム(2023年2月28日-3月1日. オンライン開催)
5th Sounding Rocket Symposium(February 28-March 1, 2023. Online Meeting)
著者人数: 21名
資料番号: SA6000185020
レポート番号: Ⅲ-5, 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS), Mar. 2023, 観測ロケットシンポジウム2022 講演集 = Proceedings of Sounding Rocket Symposium 2022, Japanese - HF-STARTプロジェクトにおけるHF帯電波伝搬の減衰の評価
佐藤駿; 中田裕之; 穂積Kornyanat; 斎藤享; 細川敬祐; 大矢浩代
2023, 大気電気学会誌(Web), 17, 1, 1882-0549, 202302253635833278 - HFドップラー観測を用いた地震に伴う異なる経路で伝搬した電離圏擾乱の解析
清水紘平; 中田裕之; 細川敬祐; 大矢浩代
2023, 大気電気学会誌(Web), 17, 1, 1882-0549, 202302296746799917 - Analysis of Traveling Ionospheric Disturbances associated with typhoons using HF Doppler and GPS radio occultation observations.
榎本陸登; 中田裕之; 細川敬祐; 大矢浩代
2023, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 154th, 202302258749585291 - Analysis of ionospheric disturbances propagating along different paths due to earthquakes using HF Doppler observations
清水紘平; 中田裕之; 細川敬祐; 大矢浩代
2023, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 154th, 202302260871465113 - S-520-3号機観測ロケット実験の初期結果報告
齋藤, 義文; 小嶋, 浩嗣; 小川, 泰信; 浅村, 和史; 阿部, 琢美; 石坂, 圭吾; 栗田, 怜; 熊本, 篤志; 田中, 真; 野村, 麗子; 細川, 敬祐; 松岡, 彩子; 横田, 勝一郎; MOEN, Joran; TRONDSEN, Espen; MILOCH, Wojciech; 滑川, 拓; SAITO, Yoshifumi; KOJIMA, Hirotsugu; OGAWA, Yasunobu; ASAMURA, Kazushi; ABE, Takumi; ISHISAKA, Keigo; KURITA, Satoshi; KUMAMOTO, Atsushi; TANAKA, Makoto; NOMURA, Reiko; HOSOKAWA, Keisuke; MATSUOKA, Ayako; YOKOTA, Shoichiro; NAMEKAWA, Taku
第4回観測ロケットシンポジウム（2022年3月14-15日. ハイブリッド開催（JAXA相模原キャンパス& オンライン）)
4th Sounding Rocket Symposium(March 14-15, 2022. Hybrid(in-person & online) Conference (Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan
著者人数: 17名
資料番号: SA6000175003
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齋藤広樹; 中田裕之; 大矢浩代; 細川敬祐
2022, 日本地球惑星科学連合大会予稿集(Web), 2022, 202302218464018431 - Overview of the SS-520-3 Sounding Rocket Experiment
齋藤義文; 小嶋浩嗣; 小川泰信; 浅村和史; 阿部琢美; 石坂圭吾; 栗田怜; 熊本篤志; 頭師孝拓; 田中真; 滑川拓; 野村麗子; 細川敬祐; 松岡彩子; 横田勝一郎; MOEN Joran; MILOCH Wojciech J.
2022, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 152nd, 202202255217646244 - Analysis of spatial distributions of Coseismic ionospheric disturbances using HFD
堀切友晃; 中田裕之; 大矢浩代; 細川敬祐
2021, 日本地球惑星科学連合大会予稿集(Web), 2021, 202202224509692200 - Characteristics of Precipitating Electrons Contributing to Dayside PsA
安倍峻平; 細川敬祐; 小川泰信
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2021, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 150th, 202202273156049709 - Relationship between ECH waves, ionospheric F-region ionization and pulsating aurora based on ground-based optical, EISCAT and Arase satellite observations
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御厨徹; 藤本晶子; 三好由純; 小川泰信; 細川敬祐
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遠山航平; 三好由純; 栗田怜; 細川敬祐; 小川泰信; 大山伸一郎; 野澤悟徳
2020, 日本地球惑星科学連合大会予稿集(Web), 2020, 202002290029673590 - Periodicity of dayside pulsating aurora: A statistical analysis in Longyearbyen
安倍峻平; 細川敬祐; 小川泰信
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浅村 和史; 三好 由純; 細川 敬祐; 滑川 拓; 三谷 烈史; 八木 直志; 吹澤 瑞貴; 坂野井 健; 菅生 真; 川島 桜也; 笠原 慧; 野村 麗子; 能勢 正仁; 小川 泰信; 齊藤 慎司; Asamura Kazushi; Miyoshi Yoshizumi; Hosokawa Keisuke; Namekawa Taku; Mitani Takefumi; Yagi Naoshi; Fukizawa Mizuki; Sakanoi Takeshi; Sugo Shin; Kawashima Oya; Kasahara Satoshi; Nomura Reiko; Nose Masahito; Ogawa Yasunobu; Saito Shinji
第2回観測ロケットシンポジウム（2019年8月5日-6日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県著者人数: 15名資料番号: SA6000142020, 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS), Aug. 2019, 観測ロケットシンポジウム2019 講演集 = Proceedings of Sounding Rocket Symposium 2019, Japanese, 120006832242 - 昼側オーロラオーバルの低緯度側に生じるフローチャネルのESR観測
田口 聡; 細川 敬祐; 小川 泰信; 家田 章正
Mar. 2019, 2018年度EISCAT研究集会 - 高エネルギー電子降下によるcosmic noise absorption(CNA)の変動とオーロラの形態変化
宮本太志朗; 大山伸一郎; 小川泰信; 細川敬祐; 栗田怜; 三好由純; 宮岡宏; 片岡龍峰; RAITA Tero
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長房勇之介; 田口聡; 小川泰信; 細川敬祐
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菅生真; 川島桜也; 浅村和史; 野村麗子; 小川泰信; 細川敬祐; 三好由純; 三谷烈史; 滑川拓; 滑川拓; 坂野井健; 吹澤瑞貴; 八木直志; 笠原慧
2019, 日本地球惑星科学連合大会予稿集(Web), 2019, ROMBUNNO.PEM11‐P24 (WEB ONLY), Japanese, 201902215532531918 - Multiple electron precipitation spots in the cusp and subsequent equatorward expansion of aurora beyond the cusp
Taguchi, Satoshi; Kohei Takasu; Keisuke Hosokawa; Yasunobu Ogawa
Nov. 2018, 第144回地球電磁気・地球惑星圏学会講演集, R006-19 - Red line aurora in the dayside cusp for northward IMF
TAGUCHI S; Y. ODA; K. HOSOKAWA
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田口聡; 織田優心; 細川敬祐
Mar. 2018, 磁気圏ダイナミクス研究集会 - 2波長観測による脈動オーロラの降下電子エネルギー推定
浅野貴紀; 三好由純; 栗田怜; 大山伸一郎; 町田忍; 細川敬祐; 小川泰信
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岸山泰輝; 細川敬祐; 野澤悟徳; 小川泰信; 大山伸一郎; 三好由純; 藤井良一; 笠原禎也; 尾崎光紀; 松田昇也; 篠原育
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長房勇之介; 田口聡; 小川泰信; 細川敬祐
2018, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 144th, ROMBUNNO.R006‐P12 (WEB ONLY), Japanese, 201902216491023241 - 石垣島で取得された630.0nm大気光観測データを用いたプラズマバブルの形状解析
高見晃平; 細川敬祐; 斎藤享; 小川泰信; 塩川和夫; 大塚雄一
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TAGUCHI S; K. HOSOKAWA; Y. OGAWA
May 2017, 日本地球惑星科学連合2017年大会講演集, PEM14-17 - 巨大な動くカスプオーロラのEISCAT観測
田口 聡; 細川 敬祐; 小川 泰信
Feb. 2017, 2016年度EISCAT研究集会 - 複数波長観測による脈動オーロラ降下電子のエネルギー推定とそのMLT依存性
浅野貴紀; 三好由純; 栗田怜; 大山伸一郎; 町田忍; 藤井良一; 細川敬祐; 小川泰信
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, 201802211411065862 - 北欧全天カメラとVan Allen Probes衛星を用いた脈動オーロラ同時観測事例の解析
川村豪; 細川敬祐; 栗田怜; 大山伸一郎; 三好由純; 小川泰信; 藤井良一; WYGANT John; BRENEMAN Aaron; BONNELL John; KLETZING Craig A.
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, 201802275970250250 - 原子大気オーロラ輝線777.4nmへの分子大気オーロラ輝線の影響評価
大山伸一郎; 細川敬祐; 小川泰信; 三好由純; 津田卓雄; 栗田怜; ANTTI Kero; 藤井良一; 野澤悟徳; 宮岡宏; 田中良昌; 田中良昌; 水野亮; 川端哲也
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, 201802281484509466 - 北欧全天カメラ及びVan Allen Probesを用いた脈動オーロラ同時観測事例の解析
川村豪; 細川敬祐; 栗田怜; 大山伸一郎; 大山伸一郎; 三好由純; 小川泰信; 藤井良一; 藤井良一; WYGANT John; BRENEMAN Aaron; BONNELL John; KLETZING Craig
2017, 極域科学シンポジウム(Web), 8th, 201802266541191618 - 南極域大気光イメージャとSwarm衛星を用いた南極域極冠パッチの統計的性質に関する研究
香川亜希子; 細川敬祐; 小川泰信; 門倉昭; 海老原祐輔
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, 201802248307524757 - ポーラーパッチならびにブロブの電子密度分布と極冠イオン対流速度の関係
吹澤瑞貴; 坂野井健; 小川泰信; 田中良昌; 細川敬祐; 田口聡; EVAN Thomas
2017, 日本地球惑星科学連合大会予稿集(Web), 2017, 201802222740845993 - ノルウェー・トロムソにおけるGNSS受信機を用いた電離圏シンチレーションと全電子数の観測
坂本明香; 大塚雄一; 小川泰信; 細川敬祐
2017, 日本地球惑星科学連合大会予稿集(Web), 2017, 201802217291578362 - ノルウェー・トロムソにおけるGNSS受信機を用いた電離圏シンチレーションの多点観測
坂本明香; 大塚雄一; 小川泰信; 細川敬祐
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, 201802269558452749 - 脈動電子オーロラのあらせ衛星および地上観測の初期結果報告:コーラス波動が駆動源と考えられる脈動オーロラパッチの時空間解析
井上拓海; 井上智寛; 尾崎光紀; 八木谷聡; 海老原祐輔; 疋島充; 細川敬祐; 今村幸佑; 門倉昭; 笠羽康正; 笠原禎也; 片岡龍峰; 加藤雄人; 小嶋浩嗣; 熊本篤志; 栗田怜; 松田昇也; 松岡彩子; 三好由純; 西山尚典; 小川泰信; 岡田雅樹; 大塚雄一; 大山伸一郎; 佐藤由佳; 塩川和夫; 田中良昌; 田中良昌; 土屋史紀; CONNORS Martin
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, ROMBUNNO.S001‐P21 (WEB ONLY), Japanese, 201802236579442399 - アイスランド~昭和基地共役点観測の現状
門倉昭; 田中良昌; 片岡龍峰; 内田ヘルベルト陽仁; 岡田雅樹; 小川泰信; 佐藤由佳; 田口真; 尾崎光紀; 塩川和夫; 細川敬祐; 三好由純; 元場哲郎; 行松彰; 山岸久雄; 佐藤夏雄
2017, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 142nd, ROMBUNNO.S001‐36 (WEB ONLY), Japanese, 201802281284186854 - Stable sun-aligned arcs equatorward of the cusp
Taguchi, S; K. Hosokawa; Y. Ogawa; T. Aoki; M. Taguchi
May 2016, 日本地球惑星科学連合2016年大会講演集, PEM18-02 - カスプの赤道側の安定したsun-aligned オーロラアーク: 全天イメージャーとEISCATの同時観測
田口 聡; 細川 敬祐; 小川 泰信
Mar. 2016, EISCATシンポジウム - 主成分分析を用いた脈動オーロラの変調解析
浅野貴紀; 三好由純; 栗田怜; 町田忍; 西山尚典; 片岡龍峰; 福田陽子; 内田ヘルベルト陽仁; 大山伸一郎; 塩川和夫; 細川敬祐; 小川泰信
2016, 極域科学シンポジウム(Web), 7th, 201702233364887794 - Sun-Aligned arcの運動メカニズム再考:3台の全天カメラと短波レーダーによる同時観測
木村洋太; 細川敬祐; 塩川和夫; 田口聡; 大塚雄一; 小川泰信
2016, 極域科学シンポジウム(Web), 7th, 201702275985676926 - Sun-aligned arcの運動メカニズム再考:3台の全天カメラと短波レーダーによる同時観測
木村洋太; 細川敬祐; 塩川和夫; 田口聡; 大塚雄一; 小川泰信
2016, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 140th, 201802220673395948 - 全天カメラで取得された脈動オーロラの画像に対する主成分分析を用いた変調解析
浅野貴紀; 三好由純; 栗田怜; 町田忍; 西山尚典; 片岡龍峰; 福田陽子; 内田ヘルベルト陽仁; 大山伸一郎; 塩川和夫; 細川敬祐; 小川泰信
2016, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 140th, 201802259878171921 - ポーラーパッチ後縁部に見られる指状構造:2次元数値シミュレーションとESRによる観測データの比較
高橋透; 平木康隆; 細川敬祐; 小川泰信; 坂井純
2016, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 140th, 201802276485674096 - 脈動オーロラが起こすナトリウム密度変動の研究:高速ナトリウムライダー観測
高橋透; 津田卓雄; 細川敬祐; 野澤悟徳; 小川泰信; 川原琢也; 斎藤徳人; 和田智之; 川端哲也; HALL Chris
2016, 日本地球惑星科学連合大会予稿集(Web), 2016, 201702217929045230 - ノルウェー・トロムソにおけるGNSS受信機による電離圏シンチレーション観測
大塚雄一; 上蔀広大; 小川泰信; 細川敬祐
2016, 日本地球惑星科学連合大会予稿集(Web), 2016, 201702261220713631 - オーロラの全天高速撮像による事例解析
内田ヘルベルト陽仁; 片岡龍峰; 門倉昭; 小川泰信; 細川敬祐
2016, 極域科学シンポジウム(Web), 7th, 201702289407883174 - オーロラの発生とGPSシンチレーションの関連性についての統計解析
加藤優作; 細川敬祐; 大塚雄一; 小川泰信; 福田陽子; 片岡龍峰; 田中正行
2016, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 140th, 201802238179741160 - 小型で安価な大気光イメージャを用いたプラズマバブルの観測
高見晃平; 細川敬祐; 斎藤享; 小川泰信
2016, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 140th, 201802260023370026 - アイスランド~昭和基地共役点観測の現状と将来
門倉昭; 田中良昌; 佐藤由佳; 片岡龍峰; 岡田雅樹; 小川泰信; 田口真; 尾崎光紀; 細川敬祐; 行松彰; 山岸久雄; 佐藤夏雄
2016, 極域科学シンポジウム(Web), 7th, OS_Kadokura_00291_01 (WEB ONLY), Japanese, 201702213626110325 - サブストーム回復相におけるオーロラパッチと下部熱圏風速変動
大山伸一郎; 塩川和夫; 三好由純; 細川敬祐; WATKINS Brenton J; 栗原純一; 津田卓雄; FALLEN Cristopher T
2016, 日本地球惑星科学連合大会予稿集(Web), 2016, ROMBUNNO.PEM16‐13 (WEB ONLY), Japanese, 201702264563477362 - Cusp aurora as a backward-elongated image of the moving region of electron precipitation
TAGUCHI Satoshi; CHIBA Yasunaga; HOSOKAWA Keisuke; OGAWA Yasunobu
May 2015, 日本地球惑星科学連合2015年大会講演集, PEM09-03 - 動く電子降下領域の後方に延びるカスプオーロラ：EISCATと全天イメージャーの同時観測
田口 聡; 千葉 康永; 細川 敬祐; 小川 泰信
Mar. 2015, EISCATシンポジウム - 夕方側オーロラオーバル内におけるオーロラアークの周期的生成
前尾友紀子; 細川敬祐; 平木康隆; 木村洋太; 井上恵一; 田口聡; 小川泰信
2015, 極域科学シンポジウム講演予稿集(CD-ROM), 6th, 201602200968677167 - IMAGE FUVとSuperDARNによる極域ジュール加熱率と沿磁力線電流の導出
尾崎直紀; 細川敬祐; 小川泰信; 藤田茂; 田中高史
2015, 極域科学シンポジウム講演予稿集(CD-ROM), 6th, 201602211775541804 - 極冠オーロラの運動メカニズム再考:2台の全天カメラと短波レーダーによる観測
木村洋太; 細川敬祐; 塩川和夫; 田口聡; 大塚雄一; 小川泰信
2015, 極域科学シンポジウム講演予稿集(CD-ROM), 6th, 201602211996828008 - 高感度全天イメージャによる観測を用いたポーラーパッチのエッジに関する統計解析
對比地雄大; 細川敬祐; 田口聡; 小川泰信; 松村充
2015, 極域科学シンポジウム講演予稿集(CD-ROM), 6th, 201602221192392423 - 夕方側オーロラオーバル内におけるオーロラアークの周期的生成
前尾友紀子; 細川敬祐; 平木康隆; 木村洋太; 井上恵一; 田口聡; 小川泰信
2015, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 138th, 201602217083245878 - IMAGE FUVとSuperDARNによる極域ジュール加熱率と沿磁力線電流の導出
尾崎直紀; 細川敬祐; 小川泰信; 藤田茂; 田中高史
2015, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 138th, 201602223247263978 - 極冠オーロラの運動メカニズム再考:2台の全天カメラと短波レーダーによる観測
木村洋太; 細川敬祐; 塩川和夫; 田口聡; 大塚雄一; 小川泰信
2015, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 138th, 201602248571375208 - 高感度全天イメージャによる観測を用いたポーラーパッチのエッジに関する統計解析
對比地雄大; 細川敬祐; 田口聡; 小川泰信; 松村充
2015, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 138th, 201602261136979927 - Postnoon auroral spotsの特性
辻本洋平; 田口聡; 細川敬祐; 小川泰信
2015, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 138th, 201602276392630508 - 小型大気光カメラによる極冠パッチの撮像
細川敬祐; 小川泰信; 田口聡
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, 201702226347160653 - 極冠パッチと共存する極冠アークの発生
坂井純; 細川敬祐; 田口聡; 小川泰信
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, 201702254531920470 - 真昼過ぎオーロラスポットと極向きにドリフトする複数のアーク
辻本洋平; 田口聡; 細川敬祐; 小川泰信
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, 201702266806395765 - 無人システムを利用したオーロラ現象の南極広域ネットワーク観測
門倉昭; 山岸久雄; 岡田雅樹; 小川泰信; 田中良昌; 元場哲郎; 細川敬祐; 才田聡子; 三好由純; 行松彰; 宮岡宏; 片岡龍峰
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, 201702287609197973 - ノルウェー・トロムソにおけるGNSS受信機を用いた電離圏シンチレーションの観測
上蔀広大; 大塚雄一; 小川泰信; 細川敬祐
2015, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 138th, 201602251863792987 - トロムソにおけるGNSS受信機を用いた電離圏シンチレーション観測
上蔀広大; 大塚雄一; 小川泰信; 細川敬祐
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, 201702269732732920 - サブストーム回復相のオーロラパッチ中に現れる下部熱圏風速変動
大山伸一郎; 塩川和夫; 三好由純; 細川敬祐; WATKINS Brenton J; 栗原純一; 津田卓雄
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, ROMBUNNO.PEM28‐09 (WEB ONLY), Japanese, 201702268380146964 - 太陽地球系現象の南北両極共役観測ネットワーク
門倉昭; 山岸久雄; 宮岡宏; 行松彰; 岡田雅樹; 小川泰信; 田中良昌; 片岡龍峰; 海老原祐輔; 田口真; 細川敬祐; 元場哲郎; 佐藤由佳
2014, 極域科学シンポジウム講演予稿集(CD-ROM), 5th, 201502290461500312 - 極方向に伝搬するカスプオーロラの動的特性:全天イメージャ観測に基づく統計解析
新山峻平; 細川敬祐; 田口聡; 小川泰信
2014, 極域科学シンポジウム講演予稿集(CD-ROM), 5th, 201502206492189592 - IMAGE FUVとSuperDARNによる極域ジュール加熱率の導出
尾崎直紀; 細川敬祐; 小川泰信
2014, 極域科学シンポジウム講演予稿集(CD-ROM), 5th, 201502212157242187 - 小型大気光カメラによるポーラーパッチの撮像
細川敬祐; 小川泰信; 田口聡
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602212176135600 - 高感度全天イメージャによる観測を用いたポーラーパッチのエッジに関する統計解析
對比地雄大; 細川敬祐; 田口聡; 小川泰信; 松村充
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602212965764633 - 高感度全天イメージャによって観測された高緯度昼間側MSTIDの特性
内海俊人; 細川敬祐; 田口聡; 小川泰信
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602220811512070 - オーロラ発光とGPSシンチレーションの関連性
三井俊平; 細川敬祐; 大塚雄一; 小川泰信; 西岡未知
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602225835492196 - 極方向に伝搬するカスプオーロラの動的特性:全天イメージャ観測に基づく統計解析
新山峻平; 細川敬祐; 田口聡; 小川泰信
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602260485823355 - EISCAT高速スキャンで観測した電離圏トラフ境界近傍の電子密度構造
石田哲朗; 小川泰信; 門倉昭; 細川敬祐; 大塚雄一
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602264988418150 - IMAGE FUVとSuperDARNによる極域ジュール加熱率の導出
尾崎直紀; 細川敬祐; 小川泰信
2014, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 136th, 201602283268986512 - オーロラ発光とGPSシンチレーションの関連性
三井俊平; 細川敬祐; 大塚雄一; 小川泰信; 西川未知
2014, 極域科学シンポジウム講演予稿集(CD-ROM), 5th, 201502246169672588 - Control system design for the optical observations of the aurora and airglow based on LabVIEW
青木 猛; 田口 聡; 細川 敬祐
Computer-based control systems play an important role in instruments for the optical observations of the aurora and airglow. We developed the control system based on LabVIEW for our new optical instrument. The LabVIEW-based system controls the Electron Multiplier CCD camera and filter turret containing passband filters. Through the robust and flexible control of these equipments the instrument can adapt to a wide range of conditions, and obtain all-sky images over a long period of time. This article focuses on the important points of the control system. The instrument was set up at Longyearbyen, Svalbard in October 2011, and obtained valuable data during the first season as was expected., 電気通信大学, 01 Feb. 2013, 電気通信大学紀要, 25, 1, 85-89, Japanese, 0915-0935, 120006315579 - 極冠オーロラの微細構造および周期性に関する研究
前尾友紀子; 細川敬祐; 田口聡; 小川泰信
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402218574305532 - 全天イメージャ観測に基づくカスプのpoleward-moving auroral formの統計的性質
新山峻平; 田口聡; 細川敬祐; 小川泰信
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402240571498262 - 電離圏カスプで同定される電子密度の周期構造:全天イメージャとEISCATの同時観測
千葉康永; 田口聡; 細川敬祐; 小川泰信
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402246938964492 - 複数の全天イメージャとレーダーを用いた極冠オーロラの広域イメージング
最所崇; 細川敬祐; 塩川和夫; 田口聡; 大塚雄一; 小川泰信
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402254772841608 - 高感度全天イメージャーによる高緯度昼間側の中規模伝搬性電離圏擾乱の観測
内海俊人; 田口聡; 細川敬祐; 小川泰信
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402270147844599 - ノルウェー・トロムソにおけるGNSS受信機を用いたシンチレーション観測
伊藤裕作; 大塚雄一; 塩川和夫; 細川敬祐; 小川泰信
2013, 極域科学シンポジウム講演予稿集(CD-ROM), 4th, 201402272011167642 - ノルウェー・トロムソにおけるGNSS受信機を用いたシンチレーション観測
伊藤裕作; 大塚雄一; 塩川和夫; 細川敬祐; 小川泰信
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402282943108258 - オーロラ爆発とGPSシンチレーションの関連性の研究
三井俊平; 細川敬祐; 大塚雄一; 小川泰信; 津川卓也
2013, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 134th, 201402293698229038 - ノルウェー・トロムソにおけるGNSSシンチレーション観測
大塚雄一; 伊藤祐作; 小川泰信; 細川敬祐
2012, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 132nd, 201302218057734655 - Plasma structuring in the polar cap ionosphere: an observation with all-sky airglow imager in Longyearbyen, Norway
HOSOKAWA KEISUKE; TAGUCHI SATOSHI; OGAWA YASUNOBU
2012, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 132nd, ROMBUNNO.B005-25, English, 201302201407864131 - Pulsating aurora seen in the dayside polar ionosphere
OGAWA YASUNOBU; HOSOKAWA KEISUKE; TAGUCHI SATOSHI; SUZUKI SHIN; KADOKURA AKIRA; MIYAOKA HIROSHI
2012, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 132nd, ROMBUNNO.B006-P027, English, 201302207967365252 - Storm-time observation of optical polar patches and electron density in evening polar cap
SAKAI JUN; HOSOKAWA KEISUKE; TAGUCHI SATOSHI; OGAWA YASUNOBU
2012, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 132nd, ROMBUNNO.B005-26, English, 201302216760169665 - Longitudinal profiles of the dayside aurora and F-region plasma parameters:Observations by all-sky imager and ESR equi-MLAT mode
TAGUCHI SATOSHI; OGAWA YASUNOBU; HOSOKAWA KEISUKE
2012, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 132nd, ROMBUNNO.B006-54, English, 201302253986799486 - 全天イメージャとEISCATレーダーの同時観測に基づく極域電離圏カスプの電子密度微細構造の周期的変動特性
千葉康永; 田口聡; 細川敬祐; 小川泰信
2012, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 132nd, ROMBUNNO.B006-P016, Japanese, 201302290237647249 - Simultaneous optical and radar observations of eastward drifting auroral forms
MOTOBA TETSUO; HOSOKAWA KEISUKE; OGAWA YASUNOBU; YUKIMATU AKIRA SESSAI; SATO NATSUO
2011, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 130th, ROMBUNNO.B010-P006, English, 201102208427499847 - Ionospheric irregularities observed by optics, GPS scintillation and HF radar during substorm
HOSOKAWA KEISUKE; OTSUKA YUICHI; OGAWA YASUNOBU; TSUGAWA TAKUYA
2011, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 130th, ROMBUNNO.B005-34, English, 201102279727096110 - Plasma temperature enhancements associated with transient flow in the cusp
TAGUCHI SATOSHI; SHIRAKAWA TAKUYA; HOSOKAWA KEISUKE; OGAWA YASUNOBU
2011, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 130th, ROMBUNNO.B006-17, English, 201102285773460005 - カスプのフローバーストに伴う電子密度の高度方向変動特性
白川拓也; 田口聡; 細川敬祐; 小川泰信
2010, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 128th, 201102222349573116 - SuperDARN北海道‐陸別HFレーダーで観測されたSAPS/SAID構造中の長・中・短周期時間変動
西谷望; 小川忠彦; 菊池崇; 海老原祐輔; 堀智昭; ZOU Yun; 細川敬祐; 片岡龍峰; 西谷望
2010, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD−ROM), 128th, ROMBUNNO.B006-20, Japanese, 201102236426868800 - SuperDARN北海道‐陸別HFレーダーの現況報告(2010.10)
西谷望; 小川忠彦; 菊池崇; 海老原祐輔; 堀智昭; 行松彰; 塩川和夫; 大塚雄一; ZOU Yun; 細川敬祐; 片岡龍峰; 久保田実; 西谷望
2010, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD−ROM), 128th, ROMBUNNO.B010-P007, Japanese, 201102241154702196 - In-situ evidence for the IMF-induced tail twisting in association with interhemispheric displacement of conjugate auroras
MOTOBA TETSUO; HOSOKAWA KEISUKE; OGAWA YASUNOBU; SATO NATSUO; KADOKURA AKIRA
2010, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 128th, ROMBUNNO.B006-01, English, 201102222313097024 - ERG計画における連携地上ネットワーク観測
塩川和夫; 西谷望; 菊池崇; 大塚雄一; 三好由純; 藤井良一; 湯元清文; 河野英昭; 吉川顕正; 篠原学; 北村健太郎; 佐藤夏雄; 行松彰; 山岸久雄; 門倉昭; 小川泰信; 田中良昌; 長妻努; 田口真; 細川敬祐; 橋本久美子; 尾崎光紀; 大矢浩代
2010, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 128th, ROMBUNNO.B006-P005, Japanese, 201102249454097910 - 北海道‐陸別HFレーダーで観測されたSAPS/SAID構造の長周期変動
西谷望; 小川忠彦; 菊池崇; 海老原祐輔; 片岡龍峰; 堀智昭; 細川敬祐; 西谷望
2009, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD−ROM), 126th, ROMBUNNO.B006-07, Japanese, 201002297724806193 - SuperDARN北海道‐陸別短波レーダーの現況報告(2009.9)
西谷望; 小川忠彦; 菊池崇; 堀智昭; 塩川和夫; 大塚雄一; 行松彰; 行松彰; 細川敬祐; 海老原祐輔; 片岡龍峰; 西谷望
2009, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD−ROM), 126th, ROMBUNNO.B010-P004, Japanese, 201002243071019180 - カスプのフローバースト領域のプラズマ構造
白川拓也; 田口聡; 細川敬祐; 小川泰信
2009, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 126th, ROMBUNNO.B005-P024, Japanese, 201002202212758960 - 北海道‐陸別HFレーダーの現状報告(2008.10)
西谷望; 西谷望; 小川忠彦; 菊池崇; 堀智昭; 細川敬祐; 海老原祐輔; 片岡龍峰
2008, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD−ROM), 124th, ROMBUNNO.B010-P016, Japanese, 200902208215203273 - 北海道‐陸別HFレーダーとGEONETで観測された大規模性電離圏擾乱のマルチイベント解析
林秀和; 西谷望; 小川忠彦; 大塚雄一; 津川卓也; 細川敬祐; 齊藤昭則
2008, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 124th, ROMBUNNO.B005-17, Japanese, 200902252716909728 - THEMISとSuperDARNの観測を用いた磁気圏尾部と電離圏の高速プラズマ流の対応
宮下幸長; 細川敬祐; 高田拓; 堀智昭; 藤本正樹; ANGELOPOULOS Vassilis; MCFADDEN James P; ULI Auster H; 行松彰; 佐藤夏雄; MENDE S.B; DONOVAN Erick
2008, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 124th, ROMBUNNO.B006-P023, Japanese, 200902221317238540 - EISCATレーダーを用いた日本の極域超高層大気観測の現状
小川泰信; 宮岡宏; 藤井良一; 野澤悟徳; 大山伸一郎; 平原聖文; 坂野井健; 阿部琢美; 小野高幸; 細川敬祐; 門倉昭; 行松彰
2008, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 124th, ROMBUNNO.S001-04, Japanese, 200902204848424710 - GPS受信機網とSuperDARNの同時観測による電離圏電子密度擾乱のスケール依存性の解明
岡本俊太; 齊藤昭則; 細川敬祐; 家森俊彦
2007, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 122nd, ROMBUNNO.B005-P027, Japanese, 200902235185926264 - 2006年12月15日に北海道‐陸別HFレーダーとGEONETで観測された大規模伝搬性電離圏擾乱
林秀和; 西谷望; 小川忠彦; 大塚雄一; 津川卓也; 細川敬祐; 齊藤昭則
2007, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 122nd, ROMBUNNO.B005-P011, Japanese, 200902248407346940 - 北海道‐陸別HFレーダーで観測された地磁気嵐時の昼間側極方向高速流
西谷望; 小川忠彦; 菊池崇; 片岡龍峰; 細川敬祐; 佐藤夏雄; 行松彰; 行松彰; 西谷望
2007, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD−ROM), 122nd, ROMBUNNO.B006-28, Japanese, 200902262957917158 - Possible observation of spatial and temporal structure of the "overshielding" from the SuperDARN Hokkaido radar
Ebihara, Y; N. Nishitani; T. Kikuchi; T. Ogawa; K. Hosokawa; M.-C. Fok
2007, SuperDARN Workshop 2007, English - Motion of the cusp and pulsed ion upflow: Simultaneous observations from IMAGE spacecraft, EISCAT and SuperDARN radars
TAGUCHI SATOSHI; OGAWA YASUNOBU; HOSOKAWA KEISUKE; MORIMOTO MINAKO; COLLIER MICHAEL R; MOORE THOMAS E; YUKIMATU AKIRA SESSAI; SATO NATSUO
2007, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 122nd, ROMBUNNO.B006-11, English, 200902279234405884 - EISCAT UHFレーダーとSuperDARN HFレーダーで観測された夕方側西向き高速イオン対流内におけるイオン加熱
前田佐和子; 小川泰信; 野澤悟徳; 細川敬祐; 津田卓雄; 大山伸一郎; BREKKE Asgeir
2007, 地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 122nd, ROMBUNNO.B005-43, Japanese, 200902278969684616
Books and other publications
- 基礎電磁気学 : 電磁気学マップに沿って学ぶ
細川, 敬祐
Japanese, vi, 156p, 東京化学同人, Apr. 2023, 9784807920358 - 南極と北極の総合誌「極地」
片岡龍峰
Japanese, Contributor, 公益財団法人日本極地研究振興会, 01 Mar. 2018 - フォトサイエンス 物理図録（改訂版）
数研出版編集部
Textbook, Japanese, Contributor, 特集5 オーロラと宇宙天気, 数研出版, 01 Nov. 2016, 9784410265136 - 低温環境の科学事典
河村公隆
Dictionary or encycropedia, Japanese, Contributor, 1-10 オーロラ, 朝倉書店, 25 Jul. 2016, 9784254161281 - フォトサイエンス 物理図録
数研出版編集部
Textbook, Japanese, Contributor, 特集5 オーロラと宇宙天気, 数研出版, 01 Feb. 2013, 9784410263125
Lectures, oral presentations, etc.
- デジタルカメラの動画撮影機能による脈動オーロラの観測例と観測計画
南條壮汰; Olivier Staiger; Urban Brändström; 津田卓雄; 青木猛; 細川敬祐
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, 名古屋大学, Domestic conference
Sep. 2022 - Overview of the ground-based optical observations during the LAMP rocket experiment in Alaska
Hosokawa, K; Y. Miyoshi
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, 名古屋大学, Domestic conference
Sep. 2022 - あらせ衛星，地上全天カメラ，EISCAT レーダーによる磁気共役同時観測を用いた脈動オーロラ電子の エネルギーに関する研究
伊藤ゆり; 細川敬祐; 小川泰信; 三好由純; 村瀬清華; 吹澤瑞貴; 大山伸一郎; 中村紗都子; 笠原禎也; 松田昇也; 笠原慧; 風間洋一; 堀智昭; 横田勝一郎; 桂華邦裕; Shiang-Yu Wang; Sunny W; Y. Tam; 篠原育
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, 名古屋大学, Domestic conference
Sep. 2022 - Internatinal joint observations of electron precipitation from Geospace using combined radio and optical techniques
Hosokawa, K; S.-I. Oyama; C. Martinez; Y. Tanaka; A. Kero; J. Manninen
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, 名古屋大学, Domestic conference
Sep. 2022 - あらせ衛星を用いたダクトによるコーラス高緯度伝搬と脈動オーロラの関係の検討
伊藤ゆり; 細川敬祐; 小川泰信; 三好由純; 吹澤瑞貴; 村瀬清華; 大山伸一郎; 中村紗都子; 笠原禎也; 松田昇也; 笠原慧; 風間洋一; 堀智昭; 横田勝一郎; 桂華邦裕; Shiang-Yu Wang; Sunny W; Y. Tam; 篠原育
Oral presentation, Japanese, ERG サイエンス会議/内部磁気圏研究集会, 東京大学, Domestic conference
Sep. 2022 - オーロラ観測のためのデジカメの校正実験と 2022 年度の観測計画
南條壮汰; Urban Brändström; 津田卓雄; 青木猛; 細川敬祐
Oral presentation, Japanese, 中間圏・熱圏・電離圏 (MTI) 研究集会, 名古屋大学, Domestic conference
Sep. 2022 - ISS からのデジタルカメラを用いたオーロラ観測で得られる画像データの特徴
南條壮汰; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫; 栗田怜
Oral presentation, Japanese, 宇宙空間からの地球超高層大気観測に関する研究会, 名古屋大学, Domestic conference
Sep. 2022 - Simultaneous conjugate observations of the energy of pulsating auroral electrons by Arase satellite, ground-based all-sky imagers and EISCAT radar
Ito, Y; K. Hosokawa; Y. Ogawa; Y. Miyoshi; K. Murase; M. Fukizawa; S.-I. Oyama; S. Nakamura; Y. Kasahara; S. Matsuda; S. Kasahara; Y. Kazama; T. Hori; S. Yokota; K. Keika; S. Wang; S. W; Y. Tam; I. Shinohara
Poster presentation, English, 20th International EISCAT Symposium 2022, Eskilstuna, Sweden, International conference
Aug. 2022 - あらせ衛星，全天カメラ，広角デジタルカメラで捉えたサブストームオンセット直後の脈動オーロラ
南條壮汰; Olivier Staiger; 門倉昭; 田中良昌; 片岡龍峰; 三好由純; 中村紗都子; 小川泰信; 笠原禎也; 松田昇也; 笠原慧; 風間洋一; 横田勝一郎; 堀智昭; 松岡彩子; 桂華邦裕; Chae-Woo Jun; 篠原育; 細川敬祐
Oral presentation, Japanese, JpGU Meeting, 幕張メッセ, Domestic conference
Jun. 2022 - 短波ドップラー観測に高度計測機能を追加するための新観測システムの検討
並木紀子; 細川敬祐; 野崎憲朗; 坂井純; 富澤一郎; 有澤豊志
Poster presentation, Japanese, JpGU Meeting, 幕張メッセ, Domestic conference
Jun. 2022 - あらせ衛星，EMCCD 全天カメラ，EISCAT レーダーによる磁気共役同時観測を用いた脈動オーロラ電子のエネルギーに関する研究
伊藤ゆり; 細川敬祐; 小川泰信; 三好由純; 大山伸一郎; 中村紗都子; 笠原禎也; 松田昇也; 篠原育
Poster presentation, Japanese, JpGU Meeting, 幕張メッセ, Domestic conference
Jun. 2022 - 航空航法用 ILS 遠距離伝搬波を用いた Es 下部構造の観測
田淵駿平; 細川敬祐; 斎藤享; 坂井純; 富澤一郎; 高橋透; 中田裕之
Poster presentation, Japanese, JpGU Meeting, 幕張メッセ, Domestic conference
Jun. 2022 - EMCCD カメラとあらせ衛星で捉えた内部変調の有無が時間的に変化したイベントの解析
南條壮汰; 江袋叡; 細川敬祐; 三好由純; 栗田怜; 中村紗都子; 大山伸一郎; 小川泰信; 笠原禎也; 笠原慧; 松岡彩子; 桂華邦裕; 堀智昭; 横田勝一郎; 松田昇也; 小路真史; 北原理弘; 今城峻; 篠原育; 藤井良一
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2022 - Diffuse Aurora の発生に寄与する降下電子の分布
安倍峻平; 細川敬祐; 小川泰信; 南條壮汰
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2022 - 衛星，高速撮像カメラ，大型大気レーダーの観測を用いた脈動オーロラ電子のエネルギーに関する研究
伊藤ゆり; 細川敬祐; 小川泰信; 三好由純; 大山伸一郎; 中村紗都子; 笠原禎也; 松田昇也; 篠原育
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2022 - トロムソにおける「多波長光学観測」の現状
細川敬祐; 大山伸一郎; 小川泰信; 三好由純; 栗田怜; 野澤悟徳
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2022 - International joint observations of electron precipitation from Geospace using combined radio and optical techniques
Hosokawa, K; S.-I. Oyama; C. Martinez; Y. Tanaka
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2022 - Tromsø AI: real-time notification service of auroral appearance in Tromsø, Norway
Sota Nanjo; Satonori Nozawa; Masaki Yamamoto; Tetsuya Kawabata; Magnar G. Johnsen; Takuo T. Tsuda; Keisuke Hosokawa
Poster presentation, English, AGU Fall Meeting, Online, International conference
Dec. 2021 - 深層学習を用いたオーロラの出現を通知するウェブアプリケーション
南條壮汰; 野澤悟徳; 山本雅毅; 川端哲也; Magnar; G. Johnsen; 津田卓雄; 細川敬祐
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「宇宙地球環境の理解に向けての統計数理的アプローチ」, Online, Domestic conference
Dec. 2021 - Relationship between Es and MSTIDs: Comparison of Doppler shift from HFD and GPS-TEC from GEONET
Matsushima, R; K. Hosokawa; J. Sakai; Y. Otsuka; M. K. Ejiri; S. Saito; M. Yamamoto; M. Nishioka; T. Tsugawa
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 150 回総会及び講演会, Online, Domestic conference
Nov. 2021 - Automated detection of mid-latitude sporadic E using GPS-TEC ROTI and aeronautical navigation radio wave data
Takahi, M; K. Hosokawa; J. Sakai; S. Saito
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 150 回総会及び講演会, Online, Domestic conference
Nov. 2021 - 昼側 PsA に寄与する降下電子に関する研究
安倍峻平; 細川敬祐; 小川泰信; 南條壮汰
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 150 回総会及び講演会, Online, Domestic conference
Nov. 2021 - Tromsø AI：ノルウェー・トロムソにおけるオーロラのリアルタイム検出システム
南條壮汰; 野澤悟徳; 山本雅毅; 川端哲也; Magnar; G. Johnsen; 津田卓雄; 細川敬祐
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 150 回総会及び講演会, Online, Domestic conference
Nov. 2021 - デジタルカメラで捉えた脈動オーロラの内部変調
南條壮汰; 細川敬祐; Olivier Staiger; 門倉昭; 田中良昌; 小川泰信; 松田昇也; 笠原禎也; 三好由純; 中村紗都子; 篠原育
Oral presentation, Japanese, あらせサイエンス会議, Online, Domestic conference
Oct. 2021 - 市民科学の促進を意識したオーロラのデジタルカメラ観測の活用例
南條壮汰; 細川敬祐; Olivier Staiger; 門倉昭; 田中良昌; 小川泰信; 松田昇也; 笠原禎也; 三好由純; 中村紗都子; 篠原育
Oral presentation, Japanese, 太陽地球系物理学分野のデータ解析手法、ツールの理解と応用研究集会, Online, Domestic conference
Sep. 2021 - 深層学習を用いたオーロラの自動検出システム：ノルウェー・トロムソにおけるリアルタイム運用
南條壮汰; 細川敬祐; 野澤悟徳; Magnar G. Johnsen
Poster presentation, English, JpGU Meeting, Online, International conference
Jun. 2021 - Simultaneous observations of plasma bubbles with an HF Doppler sounding system in Taiwan and an all-sky imager in Ishigaki Island
Sejima, H; K. Hosokawa; J. Chum; H. Nakata; J. Sakai; S. Saito
Poster presentation, English, JpGU Meeting, Online, International conference
Jun. 2021 - Automated detection of mid-latitude sporadic E using GPS-TEC ROTI data
Takahi, M; K. Hosokawa; J. Sakai; S. Saito
Poster presentation, English, JpGU Meeting, Online, International conference
Jun. 2021 - 国際宇宙ステーションからのデジタルカメラ撮像データを用いた孤立型プロトンオーロラ鉛直構造の推定
高橋一輝; 南條壮汰; 穂積裕太; 細川敬祐; 三好由純
Poster presentation, English, JpGU Meeting, Online, International conference
Jun. 2021 - ISS から観測された “Great Wall” オーロラの生成メカニズム
南條壮汰; 田中杜雄; 佐藤夏雄; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫; 栗田怜
Oral presentation, English, JpGU Meeting, Online, International conference
Jun. 2021 - Spatial distribution of pulsating aurora with/without internal modulation
Kawamura, Y; K. Hosokawa; S.-I. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; S. Ebukuro; R. Fujii
Oral presentation, Japanese, ISEE Workshop: Pulsating Aurora Workshop, Online, Domestic conference
Jan. 2021 - 深層ニューラルネットワークを用いた全天デジカメ画像のオーロラ自動検出
南條壮汰; 細川敬祐; 野澤悟徳
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2021 - 低高度衛星の光学・粒子同時観測が捉えた脈動オーロラ中に現れる inverted-V 構造
南條壮汰; 田中杜雄; 佐藤夏雄; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫; 栗田怜
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2021 - 脈動オーロラの主脈動及び内部変調に伴う降下粒子エネルギーの変動
江袋叡; 細川敬祐; 三好由純; 大山伸一郎; 小川泰信; 栗田怜; 笠原禎也; 笠原慧; 松岡彩子; 桂華邦裕; 堀智昭; 横田勝一郎; 松田昇也; 小路真史; 北原理弘; 中村紗都子; 今城峻; 篠原育; 藤井良一
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2021 - 2020 年 1 月に観測された長期の昼側 PsA イベントについて
安倍峻平; 細川敬祐; 小川泰信
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2021 - LAMP 地上サポート観測紹介
細川敬祐; 三好由純; LAMP; ロケットグループ
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2021 - 2017-2020 年の脈動オーロラ光学/レーダー観測のまとめ - あらせ衛星とのコンジャンクション観測を中心に
細川敬祐; 小川泰信; 基盤 S; 地上観測チー
Oral presentation, Japanese, 名古屋大学 ISEE 研究集会「脈動オーロラ研究集会」, Online, Domestic conference
Jan. 2021 - Overview of the Russia/Japan optical observations in 2020-2021 season
Hosokawa, K
Oral presentation, English, ISEE Workshop: Pulsating Aurora Workshop, Online, Domestic conference
Jan. 2021 - Estimation of energy of precipitating electrons causing pulsating aurora and omega band: Digital camera observations from ISS
Nanjo, S; N. Sato; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S.-I. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Oral presentation, English, American Geophysical Union Fall Meeting, Online, International conference
Dec. 2020 - Concentrically expanding ring-shaped pulsating aurora: simultaneous observations with Arase and high-speed cameras in Scandinavia
Hosokawa, K; S. Kurita; Y. Miyoshi; S.-I. Oyama; Y. Ogawa; Y. Kasahara; Y. Kasaba; S. Yagitani; M. Ozaki; S. Matsuda; F. Tsuchiya; A. Kumamoto; A. Matsuoka; R. Kataoka; K. Shiokawa; M. Shoji; S. Imajo; T. Takashima; I. Shinohara; R. Fujii
Oral presentation, English, Online, International conference
Dec. 2020 - 国際宇宙ステーションからのリム方向デジカメ観測を用いたオーロラ電子のエネルギー推定
南條壮汰; 佐藤夏雄; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 148 回総会及び講演会, Online, Domestic conference
Nov. 2020 - 昼側脈動オーロラの周期性に関する統計解析
安倍峻平; 細川敬佑; 小川泰信
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 148 回総会及び講演会, Online, Domestic conference
Nov. 2020 - Spatial distribution of pulsating aurora with/without internal modulation
Kawamura, Y; K. Hosokawa; S.-I. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; S. Ebukuro; R. Fujii
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 148 回総会及び講演会, Online, Domestic conference
Nov. 2020 - Fine scale structures of chorus elements characterizing internal modulation of pulsating aurora
Ebukuro, S; K. Hosokawa; Y. Miyoshi; S.-I. Oyama; Y. Ogawa; S. Kurita; Y. Kasahara; S. Kasahara; A. Matsuoka; K. Keika; T. Hori; S. Yokota; S. Matsuda; M. Shoji; M. Kitahara; S. Nakamura; S. Imajo; I. Shinohara; R. Fujii
Oral presentation, Japanese, Online, Domestic conference
Nov. 2020 - Propagation characteristics of Sporadic-E and MSTIDs: Statistics using HF Doppler and GPS-TEC data
Matsushima, R; K. Hosokawa; Jun Sakai; M. K. Ejiri; M. Nishioka; T. Tsugawa
Oral presentation, Japanese, Online, Domestic conference
Nov. 2020 - Polar mesospheric cloud (PMC) structures tracking with data from the meteorological satellite Himawari-8
Hozumi, Y; T. Tsuda; Y. Ando; K. Hosokawa; H. Suzuki; T. Nakamura; K. T. Murata
Oral presentation, Japanese, Online, Domestic conference
Nov. 2020 - 極中間圏雲の発生と磁気圏からの高エネルギー電子降下の関連について
細川敬祐; 津田卓雄; 穂積裕太; 安藤芳晃; 鈴木秀彦; 中村卓司; 村田 健史
Oral presentation, Japanese, Online, Domestic conference
Nov. 2020 - 国際宇宙ステーションからのデジカメ観測による脈動オーロラの広域空間特性
南條壮汰; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫; 栗田怜
Oral presentation, Japanese, 宇宙空間からの地球超高層大気観測に関する研究会, Online, Domestic conference
Sep. 2020 - HF ドップラー観測システムと GPS 全電子数観測を用いたスポラディック E と中規模伝搬性電離圏擾乱の相関について
松嶋諒; 細川敬祐; 坂井純; 江尻省; 西岡未知; 津川卓也
Oral presentation, Japanese, Online, Domestic conference
Sep. 2020 - Full-scale spatial characteristics of pulsating aurora derived from color digital camera images from the International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S.-I. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Poster presentation, English, JpGU Meeting, Online, International conference
Jul. 2020 - “Great Wall” seen in the omega band: full-color digital camera observation from the International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S.-I. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Poster presentation, English, JpGU Meeting, Online, International conference
Jul. 2020 - Simultaneous ground-satellite observation of dayside pulsating aurora
Abe, S; K. Hosokawa; Y. Ogawa
Poster presentation, English, JpGU Meeting, Online, International conference
Jul. 2020 - Observations of night time Sporadic-E layer by HF Doppler sounder network:association with Medium-Scale Traveling Ionospheric Disturbance (MSTID)
Matsushima, R; K. Hosokawa; J. Sakai; M. K. Ejiri; M. Nishioka; T. Tsugawa
Poster presentation, English, JpGU Meeting, Online, International conference
Jul. 2020 - Short review for recent studies of pulsating aurora in Japan during Arase era
Hosokawa, K; Y. Miyoshi; M. Ozaki; S.-I. Oyama; Y. Ogawa; S. Kurita; Y. Kasahara; Y. Kasaba; S. Yagitani; S. Matsuda; F. Tsuchiya; A. Kumamoto; R. Kataoka; K. Shiokawa; H. Miyaoka; Y. Tanaka; S. Nozawa; M. Teramoto; T. Takashima; I. Shinohara; R. Fujii
Poster presentation, English, JpGU Meeting, Invited, Online, International conference
Jul. 2020 - Spatial distribution of multiple temporal variations of pulsating aurora: multi-point high-speed optical observations in Scandinavia
Kawamura, Y; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; R. Fuji
Oral presentation, English, Physics of Auroral Phenomena 43rd Apatity Sminar, Apatity, Russia, International conference
Mar. 2020 - What controls the luminosity of polar cap airglow patches? : implication from airglow measurement in Eureka, Canada
Hosokawa, K; K. Shiokawa; Y. Otsuka; S. Taguchi
Oral presentation, English, American Geophysical Union Fall Meeting, San Francisco, USA, International conference
Dec. 2019 - Fine-scale temporal characteristics of pulsating aurora: dependence on background parameters in the magnetospheric source region
Ebukuro, S; K. Hosokawa; Y. Miyoshi; S. Oyama; Y. Ogawa; S. Kurita; Y. Kawamura; V. Jordanova; R. Fujii
Poster presentation, English, American Geophysical Union Fall Meeting, San Francisco, USA, International conference
Dec. 2019 - Multiple temporal variations of pulsating aurora: multi-point high-speed optical observations in Scandinavia
Kawamura, Y; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; R. Fuji
Poster presentation, English, American Geophysical Union Fall Meeting, San Francisco, USA, International conference
Dec. 2019 - Monitoring of anomalous propagation of VHF aeronautical navigation radio waves by the sporadic-E layer
Saito, S; K. Hosokawa; J. Sakai; I. Tomizawa
Poster presentation, English, American Geophysical Union Fall Meeting, San Francisco, USA, International conference
Dec. 2019 - Latitudinal and Longitudinal Variations of Pulsating Aurora Periodicities: Digital Camera Observations from International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Poster presentation, English, American Geophysical Union Fall Meeting, San Francisco, USA, International conference
Dec. 2019 - Anomalous propagation of VHF NAV signals by the sporadic E layer
Hosokawa, K; J. Sakai; I. Tomizawa; S. Saito; T. Tsugawa; M. Ishii
Oral presentation, English, EIWAC 2019, Tokyo, Japan, International conference
Oct. 2019 - 国際宇宙ステーションからのデジタルカメラ観測を用いた脈動オーロラ時空間特性の広域可視化
南條壮汰; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫; 栗田怜
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - 航空航法用 VHF 帯電波の異常伝搬と ROTI を組み合わせたスポラディック E 層の広域可視化
木村康択; 細川敬祐; 坂井純; 斎藤享; 冨澤一郎; 津川卓也; 西岡未知; 石井守
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - Large-scale signatures of pulsating aurora characterized by ambient parameters in the magnetosphere
Ebukuro, S; K. Hosokawa; Y. Miyoshi; S. Oyama; Y. Ogawa; S. Kurita; Y. Kawamura; V. Jordanova; R. Fujii
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - 低高度衛星からの光学観測を用いた磁気嵐時の孤立型プロトンオーロラの汎地球的連続観測
川合悠生; 細川 敬祐; 穂積裕太; 塩川和夫; 栗田怜; 尾崎光紀; 坂野井健; Boris Shevtsov; Igor Poddelsky; Tero Raita
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - Spatial distribution of multiple temporal variations of pulsating aurora
Kawamura, Y; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; R. Fujii
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - スポラディック E 層による計器着陸システム (ILS) 電波の異常伝搬
坂井純; 細川敬祐; 冨澤一郎; 斎藤享
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - 低高度衛星の紫外線観測を用いたオーロラオーバル赤道側境界の統計解析
京サリ; 細川敬祐; 南條壮汰; 川合悠生
Poster presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - Estimation of the altitude of pulsating aurora emission by using five-wavelength photomete
Kawamura, Y; K. Hosokawa; S. Nozawa; Y. Ogawa; T. Kawabata; R. Fujii
Poster presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - Sporadic E monitoring system using anomalous propagation of VHF radio waves for aircraft navigation
Hosokawa, K; J. Sakai; I. Tomizawa; S. Saito; T. Tsugawa; M. Nishioka; M. Ishii
Oral presentation, Japanese, 地球電磁気・地球惑星圏学会（SGEPSS）第 146 回総会及び講演会, 熊本, Domestic conference
Oct. 2019 - 国際宇宙ステーションからのデジカメ観測による脈動オーロラの広域空間特性
南條壮汰; 穂積裕太; 細川敬祐; 片岡龍峰; 三好由純; 大山伸一郎; 尾崎光紀; 塩川和夫; 栗田怜
Oral presentation, Japanese, 宇宙空間からの地球超高層大気観測に関する研究会, Online, Domestic conference
Sep. 2019 - HF ドップラー観測システムと GPS 全電子数観測を用いたスポラディック E と中規模伝搬性電離圏擾乱の相関について
松嶋諒; 細川敬祐; 坂井純; 江尻省; 西岡未知; 津川卓也
Oral presentation, Japanese, 中間圏・熱圏・電離圏 (MTI) 研究集会, Online, Domestic conference
Sep. 2019 - History and current status of ionospheric radio observations by UEC
Hosokawa, K
Oral presentation, English, URSI-Japan Radio Science Meeting, Tokyo, Japan, International conference
Sep. 2019 - Mapping of Digital Camera Images from the International Space Station: Application for Pulsating Aurora Studies
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Poster presentation, English, URSI-Japan Radio Science Meeting, Tokyo, Japan, International conference
Sep. 2019 - Large-scale characteristics of chorus waves as inferred from high-speed optical observations of pulsating aurora
Ebukuro, S; K. Hosokawa; Y. Miyoshi; S. Oyama; Y. Ogawa; S. Kurita; Y. Kawamura; V. Jordanova; R. Fujii
Poster presentation, English, URSI-Japan Radio Science Meeting, Tokyo, Japan, International conference
Sep. 2019 - Visualization of two-dimensional structure of Sporadic-E in a wide area by using air-band VHF radio observations and GPS-ROTI
Kimura, K; K. Hosokawa; J. Sakai; S. Saito; T. Tsugawa; M. Nishioka; M. Ishii; I. Tomizawa
Poster presentation, English, URSI-Japan Radio Science Meeting, Tokyo, Japan, International conference
Sep. 2019 - Continuous and global observations of isolated proton aurora from low-altitude satellite during magnetic storm
Kawai, H; K. Hosokawa; Y. Hozumi; K. Shiokawa; S. Kurita; M. Ozaki; T. Sakanoi; B. Shevtsov; I. Poddelsky; T. Raita
Poster presentation, English, URSI-Japan Radio Science Meeting, Tokyo, Japan, International conference
Sep. 2019 - The MLT dependence on the emission altitude of pulsating aurora
Kawamura, Y; K. Hosokawa; S. Nozawa; Y. Ogawa; T. Kawabata; R. Fuji
Poster presentation, English, URSI-Japan Radio Science Meeting, Tokyo, Japan, International conference
Sep. 2019 - 地上観測で見えるカスプオーロラの動的特性の紹介
細川敬祐
Oral presentation, Japanese, 地球磁気圏撮像観測に関する研究会, 宇宙科学研究所，相模原, Domestic conference
Sep. 2019 - Observations of PsA during Arase and ground-based conjunction intervals in March 2019
Hosokawa, K
Oral presentation, English, ISEE Workshop: Pulsating Aurora Workshop, Nagoya, Japan, International conference
Jul. 2019 - Fine-scale visualization of aurora in a wide area using color digital camera images from the International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Oral presentation, English, ISEE Workshop: Pulsating Aurora Workshop, Nagoya, Japan, International conference
Jul. 2019 - Large-scale characteristics of pulsating aurora periodicities: multi-point high-speed optical observations in Scandinavia
Ebukuro, S; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; Y. Kawamura; R. Fujii
Oral presentation, English, ISEE Workshop: Pulsating Aurora Workshop, Nagoya, Japan, International conference
Jul. 2019 - Latitudinal dependence of internal modulation of PsA seen in simultaneous optical observations from 4 stations in Scandinavia
Kawamura, Y; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; R. Fujii
Oral presentation, English, ISEE Workshop: Pulsating Aurora Workshop, Nagoya, Japan, International conference
Jul. 2019 - Fine-scale visualization of aurora in a wide area using color digital camera images from the International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Poster presentation, English, SuperDARN Workshop, Fuji-Yoshida, Japan, International conference
Jun. 2019 - A network of HF Doppler sounding systems in Japan: possible collaboration with SuperDARN
Hosokawa, K; H. Nakata; K. K. Hashimoto; I. Tomizawa; J. Sakai; T. Kikuchi; K. Nozaki
Poster presentation, English, SuperDARN Workshop, Fuji-Yoshida, Japan, International conference
Jun. 2019 - IMF By dependence of polar cap patch occurrence: statistics using airglow data from Eureka, Canada in comparison with SuperDARN convection patterns
Hosokawa, K; M. Nagata; K. Shiokawa; Y. Otsuka
Poster presentation, English, SuperDARN Workshop, Fuji-Yoshida, Japan, International conference
Jun. 2019 - Fine-scale visualization of aurora in a wide area using color digital camera images from the International Space Station
Nanjo, S; Y. Hozumi; K. Hosokawa; R. Kataoka; Y. Miyoshi; S. Oyama; M. Ozaki; K. Shiokawa; S. Kurita
Poster presentation, English, JpGU Meeting, Makuhari, Japan, International conference
May 2019 - Large-scale characteristics of pulsating aurora periodicities: multi-point high-speed optical observations in Scandinavia
Ebukuro, S; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; Y. Kawamura; R. Fujii
Poster presentation, English, JpGU Meeting, Makuhari, Japan, International conference
May 2019 - The Spatial characteristics of the internal modulation of pulsating aurora: multi-point high-speed optical observations in Scandinavia
Kawamura, Y; K. Hosokawa; S. Oyama; Y. Miyoshi; Y. Ogawa; S. Kurita; S. Ebukuro; R. Fujii
Poster presentation, English, JpGU Meeting, Makuhari, Japan, International conference
May 2019 - Over-darkening pulsating aurora: simultaneous observations with Arase and an all-sky camera in Scandinavia
Hosokawa, K; Y. Miyoshi; S.-I. Oyama; Y. Ogawa; S. Kurita; Y. Kasahara; M. Ozaki; Y. Kasaba; S. Yagitani; S. Matsuda; F. Tsuchiya; A. Kumamoto; I. Shinohara; R. Fujii
Oral presentation, English, JpGU Meeting, Makuhari, Japan, International conference
May 2019 - A network of HF Doppler sounding systems in Japan
Hosokawa, K; H. Nakata; K. K. Hashimoto; I. Tomizawa; J. Sakai; T. Kikuchi; K. Nozaki
Poster presentation, English, JpGU Meeting, Makuhari, Japan, International conference
May 2019 - Observations of ionospheric and mesospheric wave structures by a low-cost airglow imaging system
Hosokawa, K; N. Kusuyama; Y. Hozumi; K. Takami; S. Saito; Y. Ogawa; M. Ishii; Y. Otsuka; T. Tsugawa
Poster presentation, English, JpGU Meeting, Makuhari, Japan, International conference
May 2019 - Estimation of the altitude of pulsating aurora
川村勇貴; 細川敬祐; 野澤悟徳; 小川泰信; 川端哲也; 藤井良一
Oral presentation, Japanese, EISCAT 研究集会, 国立極地研究所，立川, Domestic conference
Mar. 2019 - Creation of polar cap patches
Hosokawa, K; S. Taguchi; Y. Ogawa
Invited oral presentation, English, American Geophysical Union, Invited, International conference
16 Dec. 2014 - Patches and TOI from 4 years observations at Resolute Bay
Hosokawa, K
Invited oral presentation, English, Cusp and Polar Cap Ionosphere Present Knowledge and Future Planning, Invited, University of Oslo, Oslo, Norway, International conference
Apr. 2009 - PMSE observed with SuperDARN
Hosokawa, K
Invited oral presentation, English, Japan-China Scientific Cooperation Program sponsored by JSPS and NSFC Joint Seminor "Study on polar ionosphere-magnetosphere coupling", Invited, JSPS and NSFC, Tokyo, International conference
2008 - Motion of large-scale structures in the polar cap ionosphere
Hosokawa, K; K. Shiokawa; Y. Otsuka; T. Ogawa
Invited oral presentation, English, Asia-Oceania Geoscience Society (AOGS) 5th Annual General Meeting, Invited, Asia-Oceania Geoscience Society (AOGS), Busan, Korea, International conference
2008 - An interhemispheric comparison of Polar Mesosphere Summer Echoes (PMSE) as detected with conjugate SuperDARN radars
Hosokawa, K; T. Ogawa; N. F. Arnold; M. Lester; N. Sato; A. S. Yukimatu
Invited oral presentation, English, Greenland IPY 2007 Space Science Symposium (GSSS-2007), Invited, Kangerlussuaq, Greenland, Denmark, International conference
2007
Courses
- 宇宙通信工学特論
The University of Electro-Communications - 宇宙通信工学特論
電気通信大学 - 大学院技術英語
The University of Electro-Communications - 大学院技術英語
電気通信大学 - 情報・通信工学基礎
The University of Electro-Communications - 情報・通信工学基礎
The University of Electro-Communications - 情報・通信工学基礎
電気通信大学 - 情報通信システム実験第二A・B
The University of Electro-Communications - 基礎演習A
The University of Electro-Communications - 基礎電磁気学
The University of Electro-Communications - 物理学概論第一
The University of Electro-Communications - 物理学概論第一
電気通信大学 - 情報通信システム実験第二A・B
The University of Electro-Communications - 情報通信システム実験第二A・B
電気通信大学 - 宇宙通信工学
The University of Electro-Communications - 電磁気学第二
The University of Electro-Communications - 電磁気学第二
The University of Electro-Communications - 電磁気学第二
電気通信大学 - 宇宙通信工学
The University of Electro-Communications - 宇宙通信工学
電気通信大学 - 基礎演習A
The University of Electro-Communications - 基礎演習A
電気通信大学 - 解析電磁気学演習
The University of Electro-Communications - 解析電磁気学演習
The University of Electro-Communications - 解析電磁気学演習
電気通信大学 - 基礎電磁気学
The University of Electro-Communications - 基礎電磁気学
電気通信大学 - 解析電磁気学
The University of Electro-Communications - 解析電磁気学
The University of Electro-Communications - 解析電磁気学
電気通信大学
Affiliated academic society
Research Themes
- 極域熱圏加熱の起源の解明：光と電波を用いた統合高解像度イメージング観測
01 Apr. 2022 - 31 Mar. 2027 - 4D sensing of polar atmosphere: space/atmosphere coupling through meso-scale auroral phenomena
Keisuke Hosokawa
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (A), 22H00173
01 Apr. 2022 - 31 Mar. 2027 - 極冠域境界に見られる熱的現象の解明：アルベーン波の観測を通したアプローチ
01 Apr. 2022 - 31 Mar. 2026 - 光と電波を用いた国際共同観測によって明らかにするジオスペース電子降下の時空間変動
07 Oct. 2021 - 31 Mar. 2026 - ディフューズオーロラ現象が放射線帯高エネルギー電子降下に与える影響の解明
05 Apr. 2021 - 31 Mar. 2026 - Passive sounding of the ionosphere using radio waves for vessel traffic services
細川 敬祐
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Challenging Research (Exploratory), 23K17699
Jun. 2023 - Mar. 2026 - 静止軌道衛星ひまわりを活用した夜光雲の特性量推定と地上光学連携観測による検証
01 Apr. 2021 - 31 Mar. 2025 - レーダ、カメラによる3D観測・解析を駆使したオーロラ3次元電流回路の高解像度復元
01 Apr. 2021 - 31 Mar. 2025 - Imaging of radiation belt loss during plasmasphere extreme erosion
尾花 由紀; 坂口 歌織; 細川 敬祐; 能勢 正仁
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), ニュージーランドのミドルマーチ観測点では2011年よりフラックスゲート磁力計が稼働して地磁気三成分の1秒値観測が行われている。ここに新しく誘導磁力計と高感度全天カメラを設置し、ULF波、VLF波、オーロラ発光の同時観測体制を確立した。 このプロジェクトでは、放射線帯効果粒子による孤立オーロラの発光と、粒子降下を引き起こすイオンサイクロトロン(EMIC)波動を同時観測することで、地球にごく近い深内部磁気圏においてEMIC波動に起因する放射線帯消失が生じていることを立証し、さらに、地磁気嵐に伴うプラズマ圏の収縮と放射線帯消失の因果関係を解明することを目指している。 これまでのところ、波動とオーロラ発光の同時出現イベントは確認されていないが、Pc 1型地磁気脈動と電離層アルフベン共振器（Ionospheric Alfven Resonator, IAR）が観測された。2020年10月6日に観測されたPc 1はIPDP（Interval of Pulsations of Diminishing Period）タイプのPc 1であり、約3-4時間の周期的な間隔で4つのPc 1イベントが観察された。これらのイベントは、北半球にあるカナダとアイスランドの4つの観測点でも同時に観測されていた。またこれと継続するようにしてIARが発生していた。この日のIARのパワースペクトル密度は10月4日と5日のIARのそれよりも強く、Pc1からIARへの波動エネルギーの移行を示しているように見える。これらの結果は、これまでの研究で提案されているように、IARが雷放電からではなくPc1脈動からも励起エネルギーが供給される可能性を示しており興味深い。 これらの研究成果は地球電磁気・地球惑星圏学会講演会で発表されたほか、現在学術誌で発表するための論文を執筆中である。, 19H01958
01 Apr. 2019 - 31 Mar. 2024 - 国際宇宙ステーションから宇宙飛行士がデジカメで撮影した画像のオーロラ研究への活用
30 Jul. 2020 - 31 Mar. 2023 - 電磁波斜め伝搬効果とオーロラ4Dイメージングによる宇宙プラズマのエネルギー写像
01 Apr. 2020 - 31 Mar. 2023 - 多地点からの地上大気光観測を用いたプラズマバブル成長過程の解明
01 Apr. 2017 - 31 Mar. 2022 - 多地点からの電波リモートセンシング観測を用いた航空航法通信環境のリアルタイムモニタリング
村田学術振興財団研究助成
01 Dec. 2020 - 30 Nov. 2021 - 電波による極端自然現象の広域リモートセンシング
高橋経済産業研究財団
01 Apr. 2019 - 31 Mar. 2021 - 国際共同による観測ロケット実験を軸とした脈動オーロラ降下電子の研究
09 Oct. 2018 - 31 Mar. 2021 - 放送衛星に影響を与える宇宙嵐をモニタリングするシステムの開発と公開
放送文化基金
01 Apr. 2019 - 31 Mar. 2020 - 電波による極端自然現象の広域リモートセンシング
高橋経済産業研究財団
01 Apr. 2019 - 31 Mar. 2020 - スポラディックE層が航空航法に与える影響を広域にモニタリングするシステムの構築
01 Apr. 2018 - 31 Mar. 2020 - 極限時間分解能観測によるオーロラ最高速変動現象の解明
01 Apr. 2015 - 31 Mar. 2020 - 人工衛星電波を用いた電離圏シンチレーション観測のカスプ・極冠域への展開
01 Apr. 2016 - 31 Mar. 2019 - ＧＰＳシンチレーション観測による極域電離圏イレギュラリティの研究
01 Apr. 2016 - 31 Mar. 2019 - 3地点からの全天大気光撮像による極冠域電離圏広域イメージング観測
01 Apr. 2014 - 31 Mar. 2019 - High precision observation of ionosphere and neutral wind with new SuperDARN imaging technique
Yukimatu Akira Sessai; Sato Natsuo; Nishitani Nozomu; Hosokawa Keisuke; Kawano Hideaki; Watanabe Masakazu; Ogawa Tadahiko
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institute of Polar Research, Grant-in-Aid for Scientific Research (B), This study could contribute to establishment of calibration methods for SuperDARN interferometry and led to more precise meteor neutral wind measurement and particularly near range echoes including neutral wind and PMSEs. This study also contributed to establishment and automation of new method for Pc5 FLR (field line resonance) detection with SuperDARN and also found a new type of geomagnetic pulsation phenomena. This also contributed to new discovery on morphology and generation mechanisms of Omega band and PMAA (poleward moving auroral arc) type aurora. This study also contributed to evaluation of solar flare influences on ionosphere and also detection of high energy particle precipitation into upper and middle atmopshere. Data with new imaging functionality could not be obtained unfortunately due to several unavoidable conditions at radar sites, but this study could still contribute to new science with new SuperDARN capabilities., 25287129
01 Apr. 2013 - 31 Mar. 2019 - 極域電離圏プラズマメソスケール密度構造のカスケード過程の解明
01 Apr. 2010 - 31 Mar. 2015 - International collaborative research of geospace by using EISCAT radar
FUJII Ryoichi; NOZAWA Satonori; MIYAOKA Hiroshi; OGAWA Yasunobu; OYAMA Shin-ichiro; SAKANOI Takeshi; FUJIWARA Hitoshi; MAEDA Sawako; TSUDA Takuo; HIRAHARA Masafumi; YUKIMATSU Akira; HOSOKAWA Keisuke; TANAKA Yoshimasa; TOKUMARU Munetoshi; ABE Takumi; MIYOSHI Yoshizumi; SHIOKAWA Kazuo; WATANABE Shigeto; ONO Takayuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nagoya University, Grant-in-Aid for Scientific Research (B), By using EISCAT radars located in northern Scandinavia and Svalbard together with other radars (MF and meteor) as well as several optical instruments (sodium LIDAR, all-sky imagers, FPI, photometer, narrow TV imagers), we have conducted a wide range of research on the geospace. Over the four years from April 2010 to March 2014, we conducted more than 40 special experiments (SPs) for 865 hours. Part of SPs were made as international collaborative experiments with other associate countries. We have obtained new findings about several topics: Cowling channel, polar cap patch, vertical oscillation of the polar ionosphere, ion-neutral collision frequency, auroral heating, travelling ionospheric disturbances. We have published 57 scientific papers. The EISCAT_3D radar is the next generation IS radar planed by the EISCAT community. We have discussed the EISCAT_3D project with Japanese colleagues as well as foreign colleagues, and have summarized a Japan's science plan using the EISCAT_3D., 22403010
01 Apr. 2010 - 31 Mar. 2014 - Conjugacy of auroras and their relationship to solar activity
SATO NATSUO; YAMAGISHI Hisao; KADOKURA Akira; OGAWA Yasunobu; YUKIMATU Akira; ONO Takayuki; HOSOKAWA Keisuke; TAGUCHI Makoto; OKANO Syoichi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institute of Polar Research, Grant-in-Aid for Scientific Research (B), Syowa Station in Antarctica and stations in Iceland form an ideal set of observatories to study geomagnetically conjugate auroras in the auroral zone. A campaign of conjugate auroral observations using all-sky TV cameras has been carried out during the equinox periods. We examined several types of auroras, e.g., beads aurora, auroral breakup, spirals, and pulsating aurora, checking for similarity and dissimilarity in terms of shapes, movements, and luminosity variations at both observatories. We assumed their generation region and mechanisms. We were also able to trace the temporal movements and displacement of the auroras in the Northern and Southern Hemispheres with a high spatial-temporal resolution. We discussed their conjugate characteristics with reference to solar wind-magnetosphere and magnetosphere-ionosphere coupling processes., 21403007
01 Apr. 2009 - 31 Mar. 2014 - Study of the upper atmosphere dynamics using highly sensitive multi-point optical instruments
SHIOKAWA Kazuo; OTSUKA Yuichi; SAITO Akinori; MIYOSHI Yoshizumi; MATSUOKA Ayako; HIRAHARA Masafumi; HOSOKAWA Keisuke; NOZAWA Satonori; OYAMA Shinichiro; OGAWA Yasunobu; IEDA Akimasa; NISHITANI Nozomu; ISHII Mamoru; KUBOTA Minoru; OGAWA Tadahiko; YAMAMOTO Mamoru
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nagoya University, Grant-in-Aid for Scientific Research (A), We have obtained various interesting results on the dynamical variations of the upper atmosphere at altitudes of 80-300 km using multi-point observation of nighttime airglow by 5 Fabry-Perot interferometers and more than 10 al-sky airglow imagers at Russia, Canada, Japan, Norway, Indonesia, Thailand, and Australia. Outstanding examples of the results are (1) various dynamical variations of medium-scale traveling ionospheric disturbances at subauroral latitudes, (2) evidence of duct propagation of small-scale gravity waves in the mesopause region, (3) evidence of a typhoon-induced small-scale gravity wave propagation to the mesopause region, and (4) relationship of eastward propagation of equatorial plasma bubbles and eastward thermospheric wind., 20244080
08 Apr. 2008 - 31 Mar. 2013 - 光学・電波観測を組み合わせたポーラーパッチの3次元イメージング観測
2011 - 2013 - 磁気圏・電離圏対流がオーロラ爆発に及ぼす影響の解明
2008 - 2010 - Multi-dimensional Simultaneous Observations of the Geospace-Ionosphere Phenomena using Low-Altitude Polar Satellites and Ground-Based Facilities
HIRAHARA Masafumi; ASAMURA Kazushi; YAMAZAKI Atsushi; SHINOHARA Iku; SAKANOI Takeshi; KASABA Yasumasa; OKANO Syoichi; MIYAOKA Hiroshi; KADOKURA Akira; OKADA Masaki; OGAWA Yasunobu; SAITO Akinori; NOZAWA Satonori; SEKI Kanako; SHIOKAWA Kazuo; IEDA Akimasa; KIKUCHI Takashi; OYAMA Shin-ichiro; EBIHARA Yusuke; TAGUCHI Makoto; HOSOKAWA Keisuke; WATARI Shinichi; MURATA Takeshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Tokyo, Grant-in-Aid for Scientific Research (B), A micro-satellite of the Japanese mission was successfully launched from Baikonur Cosmodrome in Kazakhstan on August 23, 2005. We can simultaneously observe spatial distribution and time variation of fine aurora emissions associated with auroral electron precipitation and ionospheric ion outflows with a full pitch-angle coverage and a high-time resolution. Our Reimei team has also started some collaborative observations with EISCAT, all-sky cameras, and SuperDARN. Almost every new moon interval, we have been achieving simultaneous observations with Reimei and the ground-based instruments., 19403011
2007 - 2010 - High-time resolution optical observation of auroras in the Canadian arctic
OGAWA Tadahiko; SHIOKAWA Kazuo; IEDA Akimasa; NISHITANI Nozomu; HOSOKAWA Keisuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), We conduct two campaign observations of high-time resolution all-sky auroral imaging at multi-point stations in the Canadian arctic using 1/30-sec sampled cameras, in addition to the automated routine measurements of monochromatic all-sky cameras. We also combine these observations with the THEMIS satellite measurements. From these observations we obtain fine-scale structures and their development of auroras at the beginning of auroral substorms, as well as detailed characteristics of polar-cap plasma structures., 19403010
2007 - 2010 - Investigation on the Determinative Factors in the Spectral Structure of Thermospheric Gravity Wave Disturbances
SHIBATA Takashi; TOMIZAWA Ichiro; HOSOKAWA Keisuke; SUZUKI Shin
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), HFドップラ法による電離圏擾乱の多地点観測を進め、観測データの相関解析により、中規模AGW擾乱の水平速度分散特性をより詳細に検討した。散逸効果を加味した現実的熱圏大気中での数値解析結果と比較対照することにより、AGWスペクトルの構造を支配する要素の一つとして、波動振幅の鉛直方向特性に関係するマージナル条件が重要であることが示されている。また、電離圏擾乱データに対するバイスペクトル解析によって、熱圏中での非線形AGW3波共鳴の存在とその連鎖の様子を検出することに成功している。, 19540472
2007 - 2009 - Comprehensive research on magnetosphere -ionosphere-thermosphere-mesosphere coupling process using the EISCAT radars and other instruments
FUJII Ryoichi; NOZAWA Satonori; OYAMA Shin-ichiro; OGAWA Yasunobu; EBIHARA Yusuke; MAEDA Sawako; WATANABE Shigeto; FUJIWARA Hitoshi; TAKAHASHI Yukihiro; SAKANOI Takeshi; HIRAHARA Masafumi; ASAMURA Kazushi; HOSOKAWA Keisuke; MOTOBA Tetsuo; KOIZUMI Noriko; KAWAHARA Takuya
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nagoya University, Grant-in-Aid for Scientific Research (B), EISCAT radars are one of the greatest tools in the world for observing ionospheric phenomena in the auroral, polar cusp and cap regions. EISCAT radar systems provide us with essential physical parameters over the polar ionosphere. Solar-Terrestrial Environment Laboratory (STEL) has been playing a central role in promoting a variety of research projects using the ESR and KST radars of the EISCAT Scientific Association. Both STEL and NIPR, in collaboration with researchers across the nation, have conducted about 50 Special Program (SP) experiments such as Magnetosphere-Ionosphere coupling process using simultaneous observations by REIMEI satellite and EISCAT, DELTA-2 rocket campaign, vertical wind in the lower thermosphere, wind dynamics in the lower thermosphere, ion upflow, and aurora phenomena. In the result of these activities, 29 papers have been published for 4 years., 18403010
2006 - 2009 - Understanding of the dynamics of the plasmas in the magnetosphere and polar ionosphere through remote sensing
TAGUCHI Satoshi; HOSOKAWAHOSOKAWA Keisuke; NOSE Masahito; SUZUKI Shin; MURATA Yozo
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), 地球の周辺の宇宙空間には電気を帯びた微粒子が存在しており, 様々な場所でそれぞれ固有の速さで動いている. 本研究では, その微粒子の一部が姿を変えた中性の粒子の運動を検出する撮像のデータを主に用いて, 電気を帯びた微粒子であるイオンの太陽風から磁気圏への直接的な流入, 地球磁気圏の外壁であるマグネトポーズの運動, 電離圏から磁気圏へと上昇するイオンの流れに関して, これまでに知られていない性質を見出した., 18540443
2006 - 2008 - Role of ionospheric process on the conjugate auroral dynamics and intensity
SATO Natsuo; YAMAGISHI Hisao; MIYAOKA Hiroshi; KADOKURA Akira; OKADA Masaki; ONO Takayuki; HOSOKAWA Keisuke; EJIRI Masaki; MOTOBA Tetsuo; TAGUCHI Makoto; EBIHARA Yusuke; TONEGAWA Yutaka; OKANO Shoichi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institute of Polar Research, Grant-in-Aid for Scientific Research (B), オーロラは南北両半球の極域で起こっているが、その形が似ている場合や全く異なる場合がある。南極昭和基地と北極域アイスランドは1 本の磁力線で結ばれた共役点ペアの位置関係にある。この利点を最大限活用してのオーロラの形状や動きを同時観測し、南北半球間の対称性・非対称性の特性を研究してきた。特に、爆発的オーロラ現象のオーロラ・ブレイクアップとその回復期に出現する点滅型の脈動オーロラに注目して観測研究を行なった。交付額, 17403009
2005 - 2008 - 大型短波レーダー観測網を用いた中間圏温度グローバルマップの導出
2005 - 2007 - Study on the characteristics of polar ionosphere, thermosphere and mesosphrere using SuperDARN HF radars
SATO Natsuo; KADOKURA Akira; OGAWA Tadahiko; NISHITANI Nozomu; TAGUCHI Satoshi; KEISUKE Hosokawa
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institute of Polar Research, Grant-in-Aid for Scientific Research (B), The Super Dual Auroral Radar Network (SuperDARN) is a global-scale network for HF radars capable of sensing backscatter from ionospheric irregularities in the E and F-regions of the high-latitude ionosphere. Such HF radar network has been deployed in Arctic and Antarctic regions. SENSU Syowa East and South radars in Antarctica consist of this radar network. The HF radar Doppler velocity information contained in the backscattered signals has combined to yield maps of high-latitude plasma convection and the convection electric filed. Using the SuperDARN network data we studied various large-scale and meso-scale phenomena/dynamics observed in the polar ionosphere, which occur by the processes of the magnetosphere-ionosphere coupling, and produced following results; 1) Polar mesospheric summer echo (PMSE) phenomena has been detected in Antarctic region using the near range echo obtained by the SUNSE Syowa radars and we analyzed their statistical characteristics, 2) Finding new evidences that optical pulsating auroras are associated with the same period E-region electric fluctuations, 3) EISCAT heating experiment has 'conducted in association with Finland SuperDARN radar and EISCAT, and found fine interesting temporal-spatial characteristics, 4) Optical auroras in the Cusp region showed different types for generation region and generation condition, 5) We examined Ionospheric disturbances in conjugate hemispheres during the 23 November 2003 solar eclipse using magnetometer data obtained at Syowa and Dome-Fuji in Antarctica and their conjugate observatories in Iceland, Scandinavia and Greenland together with the SuperDARN BF radars, 7) Stereo-type radar system has been installed at Syowa radar. These scientific results have been presented in the international workshops/meetings and also published to international scientific journals., 16340148
2004 - 2007 - Study of polar ionosphere and magnetosphere dynamics based on SuperDARN time series analysis technique
TSUTSUMI Masaki; HOSOKAWA Keisuke; YUKIMATU Akira
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institute of Polar Research, Grant-in-Aid for Scientific Research (C), In this study we upgraded the SuperDARN time series analysis technique [Yukimatu and Tsutsumi, 2002] by adding new capabilities to improve spatial resolutions, and also developed techniques to observe new targets such as meteors and polar mesosphere summer echoes. 1.Two techniques to improve the range resolution were newly added to the SuperDARN operating software; frequency domain interferometer(FDI) and oversampling. These techniques were first applied to meteor echo observations and proved to be useful for the study of polar mesosphere dynamics. It is notable that this meteor observation can be conducted together with the existing SuperDARN F-region observation and does not affect it at all. Network observation of polar mesosphere region is now being sought. The FDI technique was further applied to CUTLASS SuperDARN radars (Iceland and Finland) to study the minute spatial and time characteristics of irregularities which were generated by the ionosphere heating facility located at Tromso. 2.We started to develop a multi receiver imaging technique using Syowa station SuperDARN radars. A digital receiver was newly added to each of the 20 antenna outputs. Softwares to control these receivers are being developed to study fine structures of ionospheric echoes. 3.Polar mesosphere summer echoes (PMSEs) were studied by developing algorithms to detect them from near range data. Using 15 SuperDARN radars in Arctic and Antarctic regions, the occurrence rates of PMSEs were found to be different between Arctic and Antarctic and also show higher values with increasing latitudes., 16540410
2004 - 2006 - Highly Sensitive Optical Observations of Aurcraand Upper Atmosphere in the Canadian Arctic
OGAWA Tadahiko; SHIOKAWA Kazuo; OTSUKA Yuichi; IEDA Akimasa; NISHITANI Nozomu; HOSOKAWA Keisuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nagoya University, Grant-in-Aid for Scientific Research (B), Two all-sky airglow/aurora imagers were installed at two Canadian stations at Resolute Bay(RSB)and Athabasca observed polar-cap plasma patches almost always(ATH))in 2005, At RSB, we always during southward IMF periods, From two-dimensional cross-correlation analyses, we determined velocity vectors of the patches, which indicates the ionospheric convection vector, that showed high correlation with the IMF-By and -Bz variations. At ATH, we often observed isolated proton arcs and Stable Auroral Red (SAR) arcs, which were located equatorward of the amoral oval The appearance of the isolated proton arcs was highly correlated with the Pc 1 geomagnetic pulsations measured simultaneously at ATH, suggesting interactions between the electromagnetic ion cyclotron (EMK) waves and protons in the vicinity of the plasmapause and the ring current. Similar interactions without waves were also suggested for the SAR arcs, which appeared after the substorm expansion phase even without geomagnetic storm. These observations show promising capability monitor magnetospheric processes from the ground stations, whit would contribute to the future satellite projects such as THEMES, ERG, and Scope/Xscale, 16403007
2004 - 2006 - Study on the Solar Wind-Magnetosphere Interaction Based on Remote Sensing Data From IMAGE Spacecraft
TAGUCHI Satoshi; HOSOKAWA Keisuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), Observations by the Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft show that emission in the direction of the high-latitude magnetosheath is modulated in such a manner that the source shifts equatorward/poleward in the high-latitude sheath. A model based on the distributions of the sheath flux and of the number density of the hydrogen exosphere has explained these characteristics as a result of the motion of the magnetopause having an indentation at the cusp, suggesting a means for monitoring the cusp motion using IMAGE/LENA. Simultaneous observations from IMAGE/LENA and SuperDARN radar have given evidence for the means. Detailed analyses of an event of simultaneous observations from IMAGE and Polar have revealed that the high-latitude sheath emission consists of two parts : the stable emission at the higher-latitudes, and the lower-latitude emission that occurs on and off, and that that the entry of the cusp ions happens in concurrence with the appearance of the lower-latitude LENA emission. This strongly suggests that LENA monitors the entry of the ions in the cusp as well as the cusp indentation, and that the significant flux of the cusp ion entry occurs equatorward of, and separately from the cusp indentation. LENA also sometimes observes an enhanced emission in the direction of the very high-latitude magnetopause. Simultaneous observations from IMAGE/LENA and SuperDARN radar have shown that the LENA emission appears concurrently with the enhancement of the sunward flow of the reverse convection in the ionosphere. This shows that LENA can monitor the ion entry caused by cusp reconnection, and that the reconnection site moves on a time scale of several minutes. The reconnection "spot" mapped on a sphere having a radius of 8 Re shifts by approximately 1 Re over 10 minutes while fluctuating., 15540427
2003 - 2005