工学修士, 電気通信大学

工学博士, 電気通信大学

ULF, ELF, VLF帯自然電磁波,電離層擾乱, 粒子降下, 波動・粒子相互作用

昭和基地、極域、下部電離層擾乱

雷放電

電荷モーメント

雷災害、集中豪雨、竜巻

レッドスプライト

国内落雷電荷量リアルタイムマッピング

シューマン共振現象、ガンマ線フレア

地震予知

電磁波工学

異常気象、世界気候変動

国際宇宙ステーション

GLIMS

中間圏発光現象

プラズマ理工学

ULF,ELF,VLF帯自然電磁波、電離層擾乱、粒子降下、波動・粒子相互作用、

Manufacturing technology (mechanical, electrical/electronic, chemical engineering), Electrical power engineering

Social infrastructure (civil Engineering, architecture, disaster prevention), Disaster prevention engineering

Natural sciences, Space and planetary science

01 Apr. 2009
電気通信大学 電気通信学部, 教授

01 Jun. 2008 - 31 Mar. 2009
国立津山工業高等専門学校 電子制御工学科, 准教授

01 Sep. 2005 - 31 May 2008
シェフィールド大学 自動制御工学科, リサーチアソシエイト

01 Sep. 2003 - 31 Aug. 2005
スウェーデン王立宇宙物理研究所, リサーチアソシエイト

01 Apr. 2001 - 31 Aug. 2003
フランス国立学術研究センター 環境物理化学研究所, リサーチアソシエイト

01 Apr. 1999 - 31 Mar. 2001
宇宙開発事業団 地球観測データ解析システム, 招聘研究員

01 Apr. 1998 - 31 Mar. 1999
電気通信大学 電子通信学部 電子工学科, 助手

01 Apr. 1997 - 31 Mar. 1998
ロシア科学アカデミー応用物理研究所, 客員研究員

Apr. 1994 - Mar. 1997
The University of Electro-Communications, Graduate School, Division of Electro Communications, 電子工学専攻

01 Jul. 2022 - 2030
committee member, International Commission on Atmospheric Electricity (ICAE)

07 Jun. 2018 - 05 Jun. 2024
環境電磁工学研究専門委員, 電子情報通信学会 環境電磁工学研究専門委員会

07 Jun. 2018 - 05 Jun. 2024
専門委員, 電子情報通信学会環境電磁工学研究専門委員会

22 Apr. 2021 - 30 Sep. 2023
委員, 日本学術会議 電気電子工学委員会URSI分科会プラズマ波動小委員会

22 Apr. 2021 - 30 Sep. 2023
幹事, 日本学術会議 電気電子工学委員会URSI分科会

22 Apr. 2021 - 30 Sep. 2023
Designated Associate Member, Science Council of Japan, Government

22 Apr. 2021 - 30 Sep. 2023
特任連携会員, 日本学術会議, Government

22 Apr. 2021 - 30 Sep. 2023
委員, 日本学術会議 電気電子工学委員会URSI分科会電磁波の雑音・障害小委員会, Government

22 Apr. 2021 - 30 Sep. 2023
電気電子工学委員会URSI分科会電磁波の雑音・障害小委員会委員, 日本学術会議 電気電子工学委員会URSI分科会電磁波の雑音・障害小委員会, Government

19 Apr. 2021 - 30 Sep. 2023
Secretary, Japan National Committee of URSI, Society

19 Apr. 2021 - 30 Sep. 2023
主幹事, 電子情報通信学会URSI日本国内委員会, Society

25 Oct. 2022 - 10 Jun. 2023
プログラム委員, 公益社団法人日本地球惑星科学連合プログラム委員会

24 Mar. 2022 - 04 Jul. 2022
日本学術会議連携会員, 日本学術会議, Government

29 Jan. 2015 - 31 Mar. 2022
プラズマ波動小委員会委員, 日本学術会議 電気電子工学委員会 URSI分科会

29 Jan. 2015 - 31 Mar. 2022
委員, 日本学術会議 電気電子工学委員会URSI分科会プラズマ波動小委員会委員

2009 - 2022
運営委員, 日本大気電気学会, Society

01 Dec. 2020 - 10 Jun. 2021
日本地球惑星科学連合プログラム委員会委員, 公益財団法人日本地球惑星科学連合

29 Jan. 2015 - 31 Mar. 2021
電磁波の雑音・障害小委員会委員, 日本学術会議電気電子工学委員会URSI分科会

29 Jan. 2015 - 31 Mar. 2021
委員, 日本学術会議電気電子工学委員会URSI分科会 電磁波の雑音・障害小委員会

2002 - 2021
Working Group (E1 Terrestrial and Planetary Electromagnetic Noise Environment) Co-chair, URSI, Society

01 Dec. 2020
委員, 公益財団法人日本地球惑星科学連合プログラム委員会

01 Dec. 2019 - 30 Nov. 2020
科学研究費委員会専門委員, 日本学術振興会

01 Dec. 2017 - 30 Nov. 2020
専門委員, 日本学術振興会科学研究費委員会

22 Mar. 2018 - 30 Sep. 2020
電磁波の雑音・障害小委員会 委員長, 日本学術会議電気電子工学委員会URSI分科会

22 Mar. 2018 - 30 Sep. 2020
委員長, 日本学術会議電気電子工学委員会URSI分科会電磁波の雑音・障害小委員会

07 Jun. 2018 - 08 Jun. 2020
プラズマ波動小委員会委員, 電子情報通信学会 環境電磁工学研究専門委員会

07 Jun. 2018 - 08 Jun. 2020
委員, 日本学術会議 電気電子工学委員会URSI分科会プラズマ波動小委員会委員

01 Apr. 2017 - 31 Mar. 2020
運営委員, 日本大気電気学会, Society

01 Dec. 2018 - 30 Nov. 2019
科学研究費委員会専門委員, 日本学術振興会

Apr. 2016 - Mar. 2019
実行委員, ICAE2018

01 Dec. 2017 - 30 Nov. 2018
科学研究費委員会専門委員, 日本学術振興会, Others

01 Apr. 2016 - 31 Jul. 2018
運営委員会, 国際大気電気学会

Apr. 2016 - 31 Jul. 2018
プログラム委員長, 国際大気電気学会2018実行委員会

01 Jul. 2016 - 30 Apr. 2017
プログラム委員, 冬季雷シンポジウム

01 Apr. 2015 - 31 Mar. 2017
会計監査委員, 日本大気電気学会, Society

01 Sep. 2014 - 31 May 2015
プログラム委員, 日本大気電気学会, Society

1998 - 1999
選挙管理委員, 日本大気電気学会, Society

Sep. 2012
日本大気電気学会
日本大気電気学会学術研究賞

1996
URSI
URSI（国際電波連合） 若手研究者賞

First Detection of the Powerful Gamma-Ray Burst GRB 221009A by the THEMIS ESA and SST Particle Detectors on 2022 October 9
O. V. Agapitov; M. Balikhin; A. J. Hull; Y. Hobara; V. Angelopoulos; F. S. Mozer
The Astrophysical Journal Letters, American Astronomical Society, 948, 2, L21-L21, 01 May 2023, Abstract

We present the first results study of the effects of the powerful gamma-ray burst GRB 221009A that occurred on 2022 October 9, and was serendipitously recorded by electron and proton detectors on board the four spacecraft of the NASA THEMIS mission. Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars, and, among them, GRB 221009A is so far the brightest burst ever observed due to its enormous energy (E_{γ iso} ≈ 10⁵⁵ erg) and proximity (the redshift is z ≈ 0.1505). The THEMIS mission launched in 2008 was designed to study the plasma processes in the Earth’s magnetosphere and the solar wind. The particle flux measurements from the two inner magnetosphere THEMIS probes, THA and THE, and two outer probes (renamed ARTEMIS after 2010), THB and THC, orbiting the Moon captured the dynamics of GRB 221009A with a high time resolution of 4 (up to 8) measurements per second. This allowed us to resolve the fine structure of the GRB and determine the temporal scales of the two main bursts’ spiky structure, complementing the results from gamma-ray space telescopes and detectors.
Scientific journal

First Detection of Global Ionospheric Disturbances Associated with the Most Powerful Gamma Ray Burst GRB221009A
S. Pal, Y. Hobara, A. Shvets, P. W. Schnoor, M. Hayakawa, and O. Koloskov
Corresponding, Atmosphere, 14, 2, 217, 20 Jan. 2023, Peer-reviwed, False
Scientific journal, English

On the Spatio-Temporal Dependence of Anomalies in the Atmospheric Electric Field Just around the Time of Earthquakes
Y. Hobara; M. Watanabe; R. Miyajima; H. Kikuchi; T.Tsuda; M. Hayakawa
Atmosphere, 13, 1619, 04 Oct. 2022, Peer-reviwed
Scientific journal, English

Multi-Parameter Observations of Seismogenic Phenomena Related to the Tokyo Earthquake (M = 5.9) on 7 October 2021
M. Hayakawa; A. Schekotov; J. Izutsu; S. S. Yang; M. Solovieva; Y. Hobara
Geosciences, 12, 7, 265, 30 Jun. 2022, Peer-reviwed
Scientific journal, English

Spatio-Temporal Distributions of Lightning Stroke Charge Using ELF and Meteorological Data
Y. Hobara; T. Ohashi; T. Shiraishi; K. Shiokawa
Proceedings of the 6th International Conference on Electrical, Control and Computer Engineering InECCE2021, 329-337, 09 Mar. 2022, Peer-reviwed
International conference proceedings, English

Spatio-Temporal Characteristics of Energetic Lightning in Southeast Asia: Preliminary Statistical Results
S. Akama; Y. Hobara; A. Izzani Mohamed; C. Gomes; K. Shiokawa; S.Hirai; H. Kikuchi; M. Stock
Proceedings of the 6th International Conference on Electrical, Control and Computer Engineering InECCE2021, 317-327, 09 Mar. 2022, Peer-reviwed
International conference proceedings, English

Compressive Sensing to Reduce the Number of Elements in a Linear Antenna Array With a Phased Array Weather Radar
Hiroshi Kikuchi; Yasuhide Hobara; Tomoo Ushio
IEEE Transactions on Geoscience and Remote Sensing, 60, 1-10, Feb. 2022, Peer-reviwed, For weather radar, although a phased array system is useful for rapid scanning, its development cost is several times higher than that of radar with a dish-type antenna, and it requires relatively more antenna elements, analog-to-digital converters, and phase shifters. To reduce antenna elements with the devices of phased array systems, array geometry in a random or triangular pattern is often used. However, relatively fewer antenna elements result in observation accuracy degradation due to the increased sidelobe level or the wider beamwidth. We employ compressive sensing (CS) processing [i.e., L1 minimization (L1) and basis pursuit denoising (BPDN)] to reduce the number of antenna elements. We conducted numerical simulations for point and distributed like targets and discussed the observation accuracy using L1 and BPDN. Compared to the estimations made using a full array antenna, where BPDN can be estimated with extremely high accuracy given a 25% reduction in antenna elements, we also applied CS to real measurement data obtained using the PAWR. The BPDN was also very effective for measurement data. The novelty of the study is highlighted in its discussion of the feasibility of applying CS in observation data with the PAWR. The study findings provide a reference for development cost reduction and the mass production of PAWR.
Scientific journal

Validation of X-Band Multiparameter Phased-Array Weather Radar by Comparing Data from Doppler Weather Radar with a Parabolic Dish Antenna, Journal of Atmospheric and Oceanic Technology
K. Asai; H. Kikuchi; T. Ushio; Y. Hobara
Journal of Atmospheric and Oceanic Technology, 38, 9, 1561-1570, 02 Sep. 2021, Peer-reviwed
Scientific journal, English

Adaptive Beamforming Using Steering Vector Correction for Phased-Array Weather Radar
H. Kikuchi; E. Yoshikawa; T. Ushio; Y. Hobara
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Institute of Electrical and Electronics Engineers (IEEE), *, *-8426, 19 Aug. 2021, Peer-reviwed
Scientific journal, English

A Dynamical Model of Equatorial Magnetosonic Waves in the Inner Magnetosphere: A Machine Learning Approac
R. J. Boynton; S. N. Walker; H. Aryan; Y. Hobara; M. A. Balikhin
JGR Space Physics, 126, 6, *, Jun. 2021, Peer-reviwed
Scientific journal, English

Ultra-low frequency (ULF) magnetic field emissions associated with some major earthquakes occurred in Indian Subcontinent
Swati; B. Singh; D. Pundhir; A. K. Sinha; K. M. Rao; A. Guha; Y. Hobara
J. Atmos. Solar-Terr. Phys., 211, *, Dec. 2020, Peer-reviwed
Scientific journal, English

Clutter Reduction for Phased-Array Weather Radar Using Diagonal Capon Beamforming With Neural Networks
H. Kikuchi; E. Yoshikawa; T. Ushio; Y. Hobara
IEEE GEOSCIENCE AND REMOTE SENSING LETTERS, IEEE, 17, 12, 2065-2069, Dec. 2020, Peer-reviwed, The X-band phased-array weather radar (PAWR) operated by the Osaka University, performs a full-volume scan every 30 s within a 60-km range. For the waves received by the array antenna of the PAWR, digital beamforming is used only in the elevation angles. The sidelobes of the beam pattern cause errors in spectral moments in the higher elevation angles because of ground clutter. For clutter reduction, a Capon beamformer techniques with diagonal loading (CPDL) with a neural network (NN) is applied to the PAWR. In comparison with the Fourier transform beamforming method, the effectiveness of the CPDL with NN method for ground clutter reduction is discussed, using numerical simulation, and actual PAWR measurement data. Based on the simulation results and measured data, we established that the CPDL with NN accurately estimates point and distributed scatterers, which simulate ground clutter and precipitation, respectively.
Scientific journal, English

Fractal analysis of Ultra Low Frequency magnetic field emissions observed at Agra associated with two major earthquakes occurred in Pakistan
Swati; B. Singh; D. Pundhir; Y. Hobara
J.Atmos. Elect., 39, 1, 1-15, 15 Jun. 2020, Peer-reviwed
Scientific journal, English

Initial Observations for Precipitation Cores with X-Band Dual Polarized Phased Array Weather Radar
Hiroshi Kikuchi; Taku Suezawa; Tomoo Ushio; Nobuhiro Takahashi; Hiroshi Hanado; Katsuhiro Nakagawa; Masahiko Osada; Tsuyoshi Maesaka; Koyuru Iwanami; Kazuhiro Yoshimi; Fumihiko Mizutani; Masakazu Wada; Yasuhide Hobara
IEEE Transactions on Geoscience and Remote Sensing, 58, 5, 3657-3666, May 2020, Peer-reviwed, © 1980-2012 IEEE. The first X-band dual polarized phased array weather radar (DP-PAWR), which simultaneously transmits pulses of horizontal and vertical polarized radiation, was developed and installed at Saitama University, Japan, in December 2017. The DP-PAWR uses mechanical and electronic scanning at azimuth and elevation angles, respectively. It provides polarimetric precipitation measurements via 3-D volume scanning with an update rate between 10 and 60 s, for a range of up to 80 km. Here, we describe the initial DP-PAWR observation results. To evaluate the DP-PAWR observation accuracy, we compared the observational data with radar variables derived from Parsivel disdrometer data. In comparison with the disdrometer, the relative observation accuracy for the DP-PAWR radar reflectively factor had a standard deviation of 1.1 dB and mean value of 0.4 dB. We also conducted detailed observations of a developing thunderstorm using a specific differential phase (Kdp) column, focusing on the Kdp core during the storm. The Kdp core movements provided useful information about the convection flow during the storm.
Scientific journal

Low latitude VLF radio signal disturbances due to the extremely severe cyclone Fani of May 2019 and associated mesopheric response
S. Pal; S. Sarker; S. K. Midya; S. K. Mondal; Y. Hobara
JGR. Space Physics, 125, 5, 16 Apr. 2020, Peer-reviwed
Scientific journal, English

Simultaneous Study of VLF/ULF Anomalies Associated with Earthquakes in Japan
V. Singh; Y. Hobara
Open Journal of Earthquake of Research, 9, 201-215, Mar. 2020, Peer-reviwed
Scientific journal, English

Multi step ahead prediction of nighttime VLF amplitude signal for low-, mid-And high-latitude paths
H. Santosa; Y. Hobara
2017 32nd General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2017, Institute of Electrical and Electronics Engineers Inc., 2017-, 1-4, 10 Nov. 2017, Peer-reviwed, The electromagnetic field amplitude of the subionospheric Very Low Frequency (VLF) propagation is sensitive to the lower ionospheric conditions. Accordingly, VLF waves have been proposed to study and monitor the lower ionosphere (D/E region). In this paper, the NARXNN (Nonlinear Autoregressive with Exogenous Input Neural Network) is used as a method for predicting the daily nighttime mean amplitude of VLF transmitter signals indicating the ionospheric perturbation around the transmitter-receiver path. The NARXNN has a good accuracy in predicting time series data and thus are more suitable for dynamic modeling. The NARX constructed model, which was built based on daily input variables of various physical parameters with the time interval from 1 January 2011 to 4 February 2013 such as stratospheric and mesospheric temperatures, cosmic rays, total column ozone, F10.7, Kp, AE, and Dst indices. We used the constructed model to predict high-(NLK-CHF), middle-(NPM-CHF) and low-latitude (NWC-CHF) paths. As a result, the constructed models are capable of performing reasonably good 5-day ahead predictions of the daily nighttime of VLF electric field amplitude for NPM-CHF path with the Pearson correlation coefficient (r) of 0.84 and with Root Mean Square Error (RMSE) of 3.12 dB, NLK-CHF (r = 0.80, RMSE = 3.57 dB) and NWC-CHF (r = 0.79, RMSE = 2.60 dB). We conclude that the constructed NARX NN model is capable of predicting the VLF electric field amplitude variation for different latitude paths.
International conference proceedings, English

Sprites identification and their spatial distributions in JEM-GLIMS nadir observations
Mitsuteru Sato; Toru Adachi; Tomoo Ushio; Takeshi Morimoto; Masayuki Kikuchi; Hiroshi Kikuchi; Makoto Suzuki; Atsushi Yamazaki; Yukihiro Takahashi; Ryohei Ishida; Yuji Sakamoto; Kazuya Yoshida; Yasuhide Hobara
TERRESTRIAL ATMOSPHERIC AND OCEANIC SCIENCES, CHINESE GEOSCIENCE UNION, 28, 4, 545-561, Aug. 2017, Peer-reviwed, The Global Lightning and Sprite Measurements on the Japanese Experiment Module (JEM-GLIMS) started continuous nadir observations of lightning and transient luminous events (TLEs) at the International Space Station (ISS) in November 2012 and completed the observations in August 2015. As JEM-GLIMS uses the nadir observation technique, the JEM-GLIMS optical instruments simultaneously measure both incomparably intense lightning emissions and weak sprite emissions. We adopted combined data analytical methods to distinguish between these two types of emissions: (1) a subtraction of the wideband LSI-1 image from the narrowband LSI-2 image, (2) a calculation of the intensity ratio between different photometer channels, and (3) an estimation of the charge moment change (CMC) of the suspected sprite-producing CG discharge. This report presents as a case study one sprite event detected at 19: 50: 40.30580 UT on 28 September 2013 and identified using the above analytical methods. From the results derived from detailed data analyses, we judged that the optical emission measured by LSI-2 is a sprite emission. We carried out the geometry conversion toward the LSI-1 and subtracted images and found that the sprite emission location shifts by 3.5 km from the peak lightning emission location, which agree with the previous reports. The detailed horizontal distributions of sprites and the relationship between the sprite location and the parent lightning location are quantitatively revealed for the first time.
Scientific journal, English

Effects of the major sudden stratospheric warming event of 2009 on the subionospheric very low frequency/low frequency radio signals
S. Pal; Y. Hobara; S. K. Chakrabarti; P. W. Schnoor
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 122, 7, 7555-7566, Jul. 2017, Peer-reviwed, This paper presents effects of the major sudden stratospheric warming (SSW) event of 2009 on the subionospheric very low frequency/low frequency (VLF/LF) radio signals propagating in the Earth-ionosphere waveguide. Signal amplitudes from four transmitters received by VLF/LF radio networks of Germany and Japan corresponding to the major SSW event are investigated for possible anomalies and atmospheric influence on the high- to middle-latitude ionosphere. Significant anomalous increase or decrease of nighttime and daytime amplitudes of VLF/LF signals by approximate to 3-5dB during the SSW event have been found for all propagation paths associated with stratospheric temperature rise at 10hPa level. Increase or decrease in VLF/LF amplitudes during daytime and nighttime is actually due to the modification of the lower ionospheric boundary conditions in terms of electron density and electron-neutral collision frequency profiles and associated modal interference effects between the different propagating waveguide modes during the SSW period. TIMED/SABER mission data are also used to investigate the upper mesospheric conditions over the VLF/LF propagation path during the same time period. We observe a decrease in neutral temperature and an increase in pressure at the height of 75-80km around the peak time of the event. VLF/LF anomalies are correlated and in phase with the stratospheric temperature and mesospheric pressure variation, while minimum of mesospheric cooling shows a 2-3day delay with maximum VLF/LF anomalies. Simulations of VLF/LF diurnal variation are performed using the well-known Long Wave Propagating Capability (LWPC) code within the Earth-ionosphere waveguide to explain the VLF/LF anomalies qualitatively.
Scientific journal, English

One day prediction of nighttime VLF amplitudes using nonlinear autoregression and neural network modeling
H. Santosa; Y. Hobara
RADIO SCIENCE, AMER GEOPHYSICAL UNION, 52, 1, 132-145, Jan. 2017, Peer-reviwed, The electric field amplitude of very low frequency (VLF) transmitter from Hawaii (NPM) has been continuously recorded at Chofu (CHF), Tokyo, Japan. The VLF amplitude variability indicates lower ionospheric perturbation in the D region (60-90 km altitude range) around the NPM-CHF propagation path. We carried out the prediction of daily nighttime mean VLF amplitude by using Nonlinear Autoregressive with Exogenous Input Neural Network (NARX NN). The NARX NN model, which was built based on the daily input variables of various physical parameters such as stratospheric temperature, total column ozone, cosmic rays, Dst, and Kp indices possess good accuracy during the model building. The fitted model was constructed within the training period from 1 January 2011 to 4 February 2013 by using three algorithms, namely, Bayesian Neural Network (BRANN), Levenberg Marquardt Neural Network (LMANN), and Scaled Conjugate Gradient (SCG). The LMANN has the largest Pearson correlation coefficient (r) of 0.94 and smallest root-mean-square error (RMSE) of 1.19 dB. The constructed models by using LMANN were applied to predict the VLF amplitude from 5 February 2013 to 31 December 2013. As a result the one step (1 day) ahead predicted nighttime VLF amplitude has the r of 0.93 and RMSE of 2.25 dB. We conclude that the model built according to the proposed methodology provides good predictions of the electric field amplitude of VLF waves for NPM-CHF (midlatitude) propagation path.
Scientific journal, English

Multi-step Ahead Prediction of Midlatitude Daily Nighttime Subionospheric VLF Signals using NARX NN Modeling
H. Santosa; Y. Hobara; Y. Matsui
The IRAGO conference, *, Nov. 2016, Peer-reviwed
International conference proceedings, English

Identification of sprites in JEM-GLIMS nadir observations and their spatial distributions
M. Sato; T. Adachi; T. Ushio; T. Morimoto; M. Kikuchi; H. Kikuchi; M. Suzuki; A. Yamazaki; Y. Takahashi; R. Ishida; Y. Sakamoto; K. Yoshida; Y. Hobara
Terrestrial, Atmospheric and Oceanic Sciences (TAO), accepted 21 Sep. 2016., 21 Sep. 2016, Peer-reviwed
Scientific journal, English

An overview of VHF lightning observations by digital interferometry from ISS/JEM-GLIMS
Morimoto Takeshi; Kikuchi Hiroshi; Sato Mitsuteru; Ushio Tomoo; Yamazaki Atsushi; Suzuki Makoto; Ishida Ryohei; Sakamoto Yuji; Yoshida Kazuya; Hobara Yasuhide; Sano Takuki; Abe Takumi; Kawasaki Zen-Ichiro
EARTH PLANETS AND SPACE, 68, 15 Aug. 2016, Peer-reviwed

Horizontal distributions of sprites derived from the JEM-GLIMS nadir observations
M. Sato; M. Mihara; T. Adachi; T. Ushio; T. Morimoto; M. Kikuchi; H. Kikuchi; M. Suzuki; A. Yamazaki; Y. Takahashi; U. Inan; I. Linscott; R. Ishida; Y. Sakamoto; K. Yoshida; Y. Hobara
Journal of Geophysical Research: Atmospheres, 8 Apr 2016, DOI: 10.1002/2015JD024311., 08 Apr. 2016, Peer-reviwed
Scientific journal, English

Identifying the occurrence of lightning and transient luminous events by nadir spectrophotometric observation
T. Adachi; M. Sato; T. Ushio; A. Yamazaki; M. Suzuki; M. Kikuchi; Y. Takahashi; U. S. Inan; I. Linscottf; Y. Hobara; H. U. Frey; S. B. Mende; A. B. Chen; R. R. Hsu; K. Kusunoki
J. Atmos. Solar-Terr. Phys., 145, 85-97, Apr. 2016, Peer-reviwed
Scientific journal, English

Mid-latitude atmosphere and ionosphere connection as revealed by very low frequency signals
Sujay Pal; Yasuhide Hobara
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 138, 227-232, Feb. 2016, Peer-reviwed, Quantitative information about the effect of atmospheric influences on the variability of upper mesosphere-lower ionosphere (UMLI) region is not clearly known yet. To investigate the relationship between the lower atmosphere and UMLI region, we compared the amplitude of very low frequency (VLF) signals with the atmospheric parameters such as total column Ozone (TCO) density and stratospheric temperature at various heights for the first time for three different latitudinal regions. We show that the VLF amplitude is strongly correlated with the TCO density, stratospheric temperatures for mid-latitude propagation paths throughout the years. For high and low latitude regions, this correlation between the VLF amplitude and atmospheric parameters is poor and not significant. This study indicates the experimental observation of latitudinal dependence of atmospheric influence on the upper mesosphere. (C) 2015 Elsevier Ltd. All rights reserved.
Scientific journal, English

Reliability of Dual and Triple Frequency Ionosphere-free Linear Combination of GPS for Single Point Positioning
V. Satya Srinivas; Y. Hobara
The IRAGO conference, *, 2016, Peer-reviwed
International conference proceedings, English

Overview and early results of the Global Lightning and Sprite Measurements mission
Sato, M; T. Ushio; T. Morimoto; M. Kikuchi; H. Kikuchi; T. Adachi; M. Suzuki; A. Yamazaki; Y. Takahashi; U. Inan; I. Linscott; R. Ishida; Y. Sakamoto; K. Yoshida; Y. Hobara; T. Sano; T. Abe; M. Nakamura; H. Oda; Z.-I. Kawasaki
J. Geophys. Res. - Atmos., 120, 3822-3851, May 2015, Peer-reviwed
Scientific journal, English

Unexpected Very Low Frequency (VLF) Radio Events Recorded by the Ionospheric Satellite DEMETER
M. Parrot; J. J. Berthelier; J. Blecki; J. Y. Brochot; Y. Hobara; D. Lagoutte; J. P. Lebreton; F. Nemec; T. Onishi; J. L. Pincon; D. Pisa; O. Santolik; J. A. Sauvaud; E. Slominska
SURVEYS IN GEOPHYSICS, SPRINGER, 36, 3, 483-511, May 2015, Peer-reviwed, DEMETER was a low Earth orbiting microsatellite in operation between July 2004 and December 2010. Its scientific objective was the study of ionospheric perturbations in relation to seismic activity and man-made activities. Its payload was designed to measure electromagnetic waves over a large frequency range as well as ionospheric plasma parameters (electron and ion densities, fluxes of energetic charged particles). This paper will show both expected and unusual events recorded by the satellite when it was in operation. These latter events have been selected from the DEMETER database because they are rare or even have never been observed before, because they have a very high intensity, or because they are related to abnormalities of the experiments under particular plasma conditions. Some events are related to man-made radio waves emitted by VLF ground-based transmitters or power line harmonic radiation. Natural waves, such as atypical quasi-periodic emissions or uncommon whistlers, are also shown.
Scientific journal, English

Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study
K. Tatsuta; Y. Hobara; S. Pal; M. Balikhin
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 33, 11, 1457-1467, 2015, Peer-reviwed, We investigate quantitatively the effect of geomagnetic storms on the sub-ionospheric VLF/LF (Very Low Frequency/Low Frequency) propagations for different latitudes based on 2-year nighttime data from Japanese VLF/LF observation network. Three statistical parameters such as average signal amplitude, variability of the signal amplitude, and nighttime fluctuation were calculated daily for 2 years for 16-21 independent VLF/LF transmitter-receiver propagation paths consisting of three transmitters and seven receiving stations. These propagation paths are suitable to simultaneously study high-latitude, low-mid-latitude and mid-latitude D/E-region ionospheric properties. We found that these three statistical parameters indicate significant anomalies exceeding at least 2 times of their standard deviation from the mean value during the geomagnetic storm time period in the high-latitude paths with an occurrence rate of anomaly between 40 and 50% presumably due to the auroral energetic electron precipitation. The mid-latitude and low-mid-latitude paths have a smaller influence from the geomagnetic activity because of a lower occurrence rate of anomalies even during the geomagnetically active time period (from 20 to 30 %). The anomalies except geomagnetic storm periods may be caused by atmospheric and/or lithospheric origins. The statistical occurrence rates of ionospheric anomalies for different latitudinal paths during geomagnetic storm and non-storm time periods are basic and important information not only to identify the space weather effects toward the lower ionosphere depending on the latitudes but also to separate various external physical causes of lower ionospheric disturbances.
Scientific journal, English

Tsunami-driven ionospheric perturbations associated with the 2011 Tohoku earthquake as detected by subionospheric VLF signals
A. Rozhnoi; M. Solovieva; M. Hayakawa; H. Yamaguchi; Y. Hobara; B. Levin; V. Fedun
GEOMATICS NATURAL HAZARDS & RISK, TAYLOR & FRANCIS LTD, 5, 4, 285-292, Dec. 2014, Peer-reviwed, The subionospheric data from a Japanese very low frequency/low frequency (VLF/LF) receiving station at Moshiri, Hokkaido, are used to detect the response of the lower ionosphere to the tsunami triggered by the 2011 Tohoku earthquake. Disturbances in the phase and amplitude of VLF signals propagating from the transmitter in Hawaiian Islands are observed during the tsunami wave passage, and these effects in the ionosphere are compared to the in situ sea-level global positioning system (GPS) measurements near Japan. The frequency of the maximum spectral amplitude both for the VLF and GPS data is found to be in the range of periods of 8-50 min, which is likely to correspond to the period of the internal gravity waves generated by the tsunami.
Scientific journal, English

On the fine structure of dipolarization fronts
M. A. Balikhin; A. Runov; S. N. Walker; M. Gedalin; I. Dandouras; Y. Hobara; A. Fazakerley
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 119, 8, Aug. 2014, Peer-reviwed, Measurements from the closely spaced Cluster spacecraft are used to study the structure of the magnetic and electric fields within the magnetic ramp of dipolarization fronts (DF) observed close to the neutral sheet and the midnight meridian (Y-GSM < 3 R-E). The spacecraft separation was small enough (< 300 km) to treat the magnetic ramp of the DF front as a planar structure as indicated from variance analysis. The finite value of the magnetic field along the minimum variance direction for the events studied indicates that the dipolarization front structure was distinct from a tangential discontinuity. In addition to the main increase of the magnetic field in the maximum variance component, strong oscillations were observed in the intermediate component. The presence of this oscillatory structure results in an expansion of the region in which a change of magnetic pressure occurs, the size of which is typically an ion Larmor radius or greater. This widening is important in maintaining the pressure balance at the edge of the DF. This phenomenon resembles observations of intense current sheets in the magnetotail and also laboratory experiments of current sheet formation, in which a similar widening of the ramp region has been observed. In this paper we argue against the idea that an electron temperature anisotropy, resulting in electron curvature currents, can explain the formation of the oscillatory structures observed at DFs. These oscillations can be explained as eigenmode waves of the plasma that propagate away from the disturbance (DF) that is moving at subsonic speeds. Oscillations observed within the magnetic ramp indicate field-aligned currents that are expected to be associated with DF.
Scientific journal, English

Multi-Point Detection of the Elf Transient Caused by the Gamma Flare of December 27, 2004
A. P. Nickolaenko; A. Yu. Schekotov; M. Hayakawa; Y. Hobara; G. Satori; J. Bor; M. Neska
RADIOPHYSICS AND QUANTUM ELECTRONICS, SPRINGER, 57, 2, 125-140, Jul. 2014, Peer-reviwed, We present the experimental records of the radio pulse related to the gamma burst that took place on December 27, 2004. The records, which are synchronized by GPS time marks, were obtained in the observatories at Moshiri and Onagawa (Japan), Esrange (Sweden), Karimshino (Kamchatka, Russia), Nagycenk (Hungary), and Hornsund (Polish Polar Station Spitzbergen). The data demonstrate exceptional similarity and contain characteristic pulses that correspond to the time of gamma-ray arrival. Processing of the signals shows that along with the time match, the following modeling predictions are confirmed: radio pulses contain a signal at the main frequency of the Schumann resonance, the field source has positive polarity (the current is directed from the ionosphere towards the Earth), the polarization of the horizontal magnetic field of the radio wave is almost linear, and the directions towards the source indicate the epicenter of the gamma-quanta flux collision with the ionosphere. These properties correspond to the concept of the parametric electromagnetic pulse that is produced due to a significant change in the current in the global electric circuit, which is caused by a cosmic gamma-ray flare.
Scientific journal, English

Detection of tsunami-driven phase and amplitude perturbations of subionospheric VLF signals following the 2010 Chile earthquake
A. Rozhnoi; S. Shalimov; M. Solovieva; B. Levin; G. Shevchenko; M. Hayakawa; Y. Hobara; S. N. Walker; V. Fedun
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 119, 6, 5012-5019, Jun. 2014, Peer-reviwed, We report on specific fluctuations in phase and amplitude of VLF signals that correlate both spatially and temporally with the passage of the tsunamis recorded by the Deep-ocean Assessments and Reporting of Tsunamis bottom pressure stations. Measurements from the VLF/LF receiver sited in Petropavlovsk-Kamchatsky and sensor buoys placed throughout the Pacific Ocean at great distances (Hawaii and Japan) from the epicenter are consistent with the hypothesis that the ocean tsunami following the Chile earthquake on 27 February 2010 radiated internal gravity waves which propagated through the lower ionosphere.
Scientific journal, English

X-rays and solar proton event induced changes in the first mode Schumann resonance frequency observed at a low latitude station Agra, India
Birbal Singh; Rajesh Tyagi; Yasuhide Hobara; Masashi Hayakawa
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 113, 113, 1-9, Jun. 2014, Peer-reviwed, Effects of two events of X-ray bursts followed by solar proton events (SPEs) occurred on 22 September, 2011 and 06 July, 2012 on the variation of first mode Schumann resonance (SR) frequency monitored at a low latitude station, Agra (Geograph. lat. 27.2 degrees N, long. 78 degrees E) India are examined. The variation of average first mode SR frequency shows a sudden increase in coincidence with the X-ray bursts and a decrease associated with the peak flux of SPE. The increases in the frequency in the two cases are 8.4% and 10.9% and corresponding decreases are 4.3% and 3.3% respectively. The increases in the frequency are interpreted in terms of growth of ionization in the upper part of D-region ionosphere due to X-ray bursts and decreases during SPE are caused by the high ionization in the lower D-region (altitude about 50-60 km) in the polar region. The variation of SR frequency is observed to be consistent with other observatories at middle and high latitudes. The effects of X-ray flares on the D-region of the ionosphere at low and equatorial latitudes are also examined by analyzing the amplitude data of VLF transmitter signal (NWC, f=19.8 kHz) monitored at Agra. The flare effect observed prior to sun-set hours shows increase of electron density above 60 km in the ionosphere. (C) 2014 Elsevier Ltd. All rights reserved.
Scientific journal, English

Deducing Locations and Charge Moment Changes of Lightning Discharges by ELF Network Observations in Japan
Y. Hobara; T. Inoue; M. Hayakawa; K. Shiokawa
ICAE2014, **, **, **-**, Jun. 2014, Peer-reviwed
International conference proceedings, English

Summer Thunderstorm Associated with Cluster of Blue Jets and Starters in Japan
T.Suzuki; M.Hayakawa; Y.Hobara; K.Kusunoki
ICAE 2014, **, **, **-**, Jun. 2014, Peer-reviwed
International conference proceedings, English

Detection of tsunami-driven phase and amplitude perturbations of subionospheric VLF signals following the 2010 Chile earthquake
A. Rozhnoi; S. Shalimov; M. Solovieva; B. Levin; G. Shevchenko; M. Hayakawa; Y. Hobara; S. N. Walker; V. Fedun
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 119, 6, 5012-5019, Jun. 2014, Peer-reviwed, We report on specific fluctuations in phase and amplitude of VLF signals that correlate both spatially and temporally with the passage of the tsunamis recorded by the Deep-ocean Assessments and Reporting of Tsunamis bottom pressure stations. Measurements from the VLF/LF receiver sited in Petropavlovsk-Kamchatsky and sensor buoys placed throughout the Pacific Ocean at great distances (Hawaii and Japan) from the epicenter are consistent with the hypothesis that the ocean tsunami following the Chile earthquake on 27 February 2010 radiated internal gravity waves which propagated through the lower ionosphere.
Scientific journal, English

The origin of spectral resonance structures of the ionospheric Alfven resonator. Single high-altitude reflection or resonant cavity excitation?
E. Fedorov; A. Schekotov; Y. Hobara; R. Nakamura; N. Yagova; M. Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 119, 4, 3117-3129, Apr. 2014, Peer-reviwed, A common view is that spectral maxima in observed spectral resonance structures (SRS) of ionospheric Alfven resonator (IAR) at frequencies f<5 Hz are the signature of resonance frequencies of the IAR. We have studied not only spectra but also waveforms of magnetic fluctuations at IAR frequencies registered at Moshiri station (Japan) and have found that there exist two kinds of signals. The dominant type of signal is a pair of pulses which is caused by an initial exciting impulse and accompanied by a single reflection from the top boundary of the IAR. In the absence of reflection from the lower ionosphere, such signals are not resonant and hence are not caused by IAR excitation. The minority of cases are trains of three or more pulses separated by a nearly constant time interval reflected from both IAR boundaries. We have found that different kinds of signals in time domain may correspond to similar comb-shaped Fourier spectra. So different kinds of signals in time domain practically cannot be distinguished on the basis of their Fourier spectra. We have calculated waveforms and SRS structures of the magnetic field oscillations generated by a model lightning discharge and IAR resonant frequencies. Calculated IAR resonance frequencies can be in disagreement with those of spectral maxima of pulse trains. Then, an analysis of signal waveforms in time domain is highly required to estimate IAR resonance frequencies.
Scientific journal, English

Surface displacements in Japan before the 11 March 2011 M9.0 Tohoku-Oki earthquake
Chieh-Hung Chen; Strong Wen; Jann-Yenq Liu; Katsumi Hattori; Peng Han; Yasuhide Hobara; Chung-Ho Wang; Ta-Kang Yeh; Horng-Yuan Yen
JOURNAL OF ASIAN EARTH SCIENCES, PERGAMON-ELSEVIER SCIENCE LTD, 80, 165-171, Feb. 2014, Peer-reviwed, Daily resolution data retrieved from the 1243 ground-based Global Positioning System (GPS) stations in Japan are utilized to expose surface displacements before the destructive M9 Tohoku-Oki earthquake (March 11, 2011). Variations in the residual GPS data, in which effects of the long-term plate movements, short-term noise and frequency-dependent variations have been removed through a band-pass filter via the Hilbert-Huang transform, are compared with parameters of the focal mechanism associated with the Tohoku-Oki earthquake for validation. Analytical results show that the southward movements, which were deduced from the residual displacements and agree with the strike of the rupture fault, became evident on the 65th day before the Tohoku-Oki earthquake. This observation suggests that the shear stress played an important role in the seismic incubation period. The westward movements, which are consistent with the angle of the maximum horizontal compressive stress, covered entire japan and formed an impeded area (142 E, 42 degrees N) about 75 km away from the epicenter on the 47th day prior to the earthquake. The horizontal displacements integrated with the vertical movements from the residual GPS data are very useful to construct comprehensive images in diagnosing the surface deformation from destructive earthquakes along the subduction zone. (C) 2013 Elsevier Ltd. All rights reserved.
Scientific journal, English

Estimating the lower ionosphere height and lightning location using multimode "tweek" atmospherics
A. V. Shvets; T. M. Serdiuk; Y. V. Gorishnyaya; Y. Hobara; M. Hayakawa
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 108, 1-9, Feb. 2014, Peer-reviwed, There is proposed a new method of estimating the effective ionospheric height of the Earth-ionosphere waveguide and the propagation distance of tweek-atmospherics. It is based on the compensation of waveguide frequency dispersion of a tweet signal, which enables us to improve the accuracy of deducing the cutoff frequencies, especially in the presence of noise. An approach to solve the inverse problem is suggested that reduces the task of finding both the source range and the waveguide cutoff frequencies by using the multimode characteristics of tweeks to an issue of one-dimensional optimization. Based on the numerical modeling of multimode tweek-atmospherics in the Earth-ionosphere waveguide with exponential vertical conductivity profile of the lower ionosphere, it was shown that the accuracy of estimating the effective waveguide height by the new method is good as about 100-400 m for the first and higher order modes. It then allows us to estimate the parameters of vertical conductivity profile of the lower ionosphere for a wide range of source distances from a few hundred to a few thousand kilometers, as long as two or more tweek harmonics can be detected. Preliminary analysis of experimental tweek records show a decrease of the effective height with increasing the mode number, and the scale height of the exponential vertical conductivity profile for the isotropic lower ionosphere model is estimated to be in a range of 0.4-2.5 km. (C) 2013 Published by Elsevier Ltd.
Scientific journal, English

Detection of tsunami-driven phase and amplitude perturbations of subionospheric VLF signals following the 2010 Chile earthquake
A. Rozhnoi; S. Shalimov; M. Solovieva; B. Levin; G. Shevchenko; M. Hayakawa; Y. Hobara; S. N. Walker; V. Fedun
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 119, 6, 5012-5019, 2014, Peer-reviwed, We report on specific fluctuations in phase and amplitude of VLF signals that correlate both spatially and temporally with the passage of the tsunamis recorded by the Deep-ocean Assessments and Reporting of Tsunamis bottom pressure stations. Measurements from the VLF/LF receiver sited in Petropavlovsk- Kamchatsky and sensor buoys placed throughout the Pacific Ocean at great distances (Hawaii and Japan) from the epicenter are consistent with the hypothesis that the ocean tsunami following the Chile earthquake on 27 February 2010 radiated internal gravity waves which propagated through the lower ionosphere. ©2014. American Geophysical Union. All Rights Reserved.
Scientific journal, English

The origin of spectral resonance structures of the ionospheric Alfvén resonator. Single high-altitude reflection or resonant cavity excitation?
E. Fedorov; A. Schekotov; Y. Hobara; R. Nakamura; N. Yagova; M. Hayakawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 119, 4, 3117-3129, 2014, Peer-reviwed, A common view is that spectral maxima in observed spectral resonance structures (SRS) of ionospheric Alfvén resonator (IAR) at frequencies f<
5 Hz are the signature of resonance frequencies of the IAR. We have studied not only spectra but also waveforms of magnetic fluctuations at IAR frequencies registered at Moshiri station (Japan) and have found that there exist two kinds of signals. The dominant type of signal is a pair of pulses which is caused by an initial exciting impulse and accompanied by a single reflection from the top boundary of the IAR. In the absence of reflection from the lower ionosphere, such signals are not resonant and hence are not caused by IAR excitation. The minority of cases are trains of three or more pulses separated by a nearly constant time interval reflected from both IAR boundaries. We have found that different kinds of signals in time domain may correspond to similar comb-shaped Fourier spectra. So different kinds of signals in time domain practically cannot be distinguished on the basis of their Fourier spectra. We have calculated waveforms and SRS structures of the magnetic field oscillations generated by a model lightning discharge and IAR resonant frequencies. Calculated IAR resonance frequencies can be in disagreement with those of spectral maxima of pulse trains. Then, an analysis of signal waveforms in time domain is highly required to estimate IAR resonance frequencies. Key Points Observed spectra at f <
5 Hz are usually the comb-shaped spectra of 2-3 pulses Comb-shaped spectra are not always the signature of IAR resonance frequencies Calculated IAR response to a lightning coincides with the observed pulse trains ©2014. American Geophysical Union. All Rights Reserved.
Scientific journal, English

Deducing Locations and Electrical properties of Lightning Discharges by ELF Network Observations in Japan
Yasuhide Hobara; Masashi Hayaka; Kazuo Shiokawa
2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS), IEEE, 2014, Peer-reviwed
International conference proceedings, English

Spatio-temporal characteristics of sub-ionospheric perturbations associated with annular solar eclipse over Japan: Network observations and modeling
Daiki Inui; Yasuhide Hobara
2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS), IEEE, 2014, Peer-reviwed, The UEC's VLF/LF transmitter observation network has been operating years in order to monitor the ionospheric perturbations caused by various physical phenomena. A solar eclipse is one of the factors that produce disturbances in the lower ionosphere. In this paper, we analyze VLF amplitude data from our network associated with annular solar eclipse in 2012. Clear temporal dependences of the VLF/LF amplitude were identified at various VLF/LF receivers. Numerical computations of VLF/LF signals with the ionospheric perturbations due to the solar eclipse were carried out by using 2D-FDTD method. As a result, temporal variations of the VLF/LF amplitude are in rather good agreement with those from the numerical modeling.
International conference proceedings, English

Simultaneous observations of ionospheric disturbances from VLF transmitter signals and surface displacements from GPS related to inland earthquakes over Japan
Yasuhde Hobara; Risa Miyake; C. -H. Chen
2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS), IEEE, **, **, NH33B, 2014, Peer-reviwed, Ionospheric anomalies have been reported for years before major seismic activities by using VLF transmitter signals. Although possible generation mechanisms of the precursory perturbations have been proposed such as anomalous electric field and atmospheric waves originated around the future epicenter, the experimental evidence indicating the coupling between the lithospheric activities and overlaying ionosphere before seismic events has not been confirmed.
In this paper we analyze the VLF transmitter amplitude data from UEC's VLF observation network identifying the ionospheric perturbations together with frequency dependent filtered surface displacement data from high density GPS network for inland earthquakes in Japan during several consecutive years to study the LAIC mechanism.
We found that both ionospheric perturbations and surface displacements occurred almost simultaneously about one week before for some of the shallow earthquakes indicative of coupling between the precursory ground movement and relevant ionospheric perturbations. Either ionospheric or GPS anomalies were also found for other earthquakes. We are also going to discuss the significance of types of earthquakes for LAIC mechanism.
International conference proceedings, English

Global Lightning and Sprite Measurements from International Space Station
Tomoo Ushio; Mitsuteru Sato; Takeshi Morimoto; Hiroshi Kikuchi; Makoto Suzuki; Atsushi Yamazaki; Yasuhide Hobara; Toru Adachi
2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS), IEEE, **, **, **-**, 2014, Peer-reviwed, The Global Lightning and sprIte MeasurementS (GLIMS) on the International Space Station (ISS) is a mission to detect and locate optical transient luminous events (TLEs) and its associated lightning simultaneously from the non-sun synchronous orbit, and is scheduled to be launch from Japan in January, 2012 as part of the multi-mission consolidated equipment on Japanese Exposure Module (JEM). Our mission goals are (1) to detect and locate lightning and sprite within storm scale resolution over a large region of the Earth's surface along the orbital track of the ISS without any bias, (2) to clarify the generation mechanism of sprite, and (3) to identify the occurrence conditions of TLEs. To achieve these goals, two CMOS cameras, six Photometers, VLF receiver, and VHF interferometer with two antennas, are installed at the bottom of the module to observe the TLEs as well as causative lighting discharges at nadir direction during day and night time. Though the luminous events so-called sprite, elves and jets have been investigated by numerous researchers all over the world based mainly on the ground observations, some important problems have not been fully understood yet such as generation mechanisms of columniform fine structure and horizontal offset of some sprites from the parent lightning discharges. In the JEM-GLIMS mission, observations from our synchronized sensors are going to shed light on above-mentioned unsolved problems regarding TLEs as well as causative lighting discharges. In this presentation, the scientific background, instrumentation, project summaries and initial observation results are given.
International conference proceedings, English

Ground-based observations of the relations between lightning charge-moment-change and the physical and optical properties of column sprites
Roy Yaniv; Yoav Yair; Colin Price; Jo'zsef Bor; Mitsutero Sato; Yasuhide Hobara; Steve Cummer; Jingbo Li; Adam Devir
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 107, 107, 60-67, Jan. 2014, Peer-reviwed, Optical observations of 66 sprites, using a calibrated commercial CCD camera, were conducted in 20092010 and 2010-2011 winter seasons as part of the ILAN (Imaging of Lightning And Nocturnal flashes) campaign in the vicinity of Israel and the eastern Mediterranean. We looked for correlations between the properties of parent lightning (specifically, the charge moment change; CMC) to the properties of column sprites, such as the measured radiance, the length and the number of column elements in each sprite event. The brightness of sprites positively correlates with the CMC (0.7) and so does the length of sprite elements (0.83). These results are in agreement with previous studies, and support the QE model of sprite generation. (C) 2013 Elsevier Ltd. All rights reserved.
Scientific journal, English

Ionospheric effects of the Mt. Kirishima volcanic eruption as seen from subionospheric VLF observations
A. Rozhnoi; M. Hayakawa; M. Solovieva; Y. Hobara; V. Fedun
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 107, 107, 54-59, Jan. 2014, Peer-reviwed, Data from the Pacific network of VLF receivers have been used to study the response of the lower ionosphere to the January 2011 Mt. Kirishima (South Japan) volcanic eruption. A major explosive eruption occurred on January 27, which was preceded by several small eruptions. Perturbations of nighttime subionospheric VLF signals have been detected on the day of the first small eruption on January 18 (UT) with the maximum observed about 1.5 h after the eruption. The nighttime signal remained disturbed during the subsequent pre-eruptive and eruptive activity of Mt. Kirishima. The daytime perturbations were not observed. The frequency of the maximum spectral amplitude was found to be in the range of periods of 6-30 min, which corresponds to the periods of internal gravity waves. These results suggest that the observed VLF ionospheric effects can possibly be produced by the penetration of gravity waves caused by the volcanic activity into the ionosphere. (C) 2013 Elsevier Ltd. All rights reserved.
Scientific journal, English

Simultaneous study of ULF/VLF anomalies associated with earthquakes occurred in Japan” in session
Y. Hobara
AGU Fall Meeting, **, **, NH33B, Dec. 2013, Peer-reviwed
International conference proceedings, English

The dynamic quasiperpendicular shock: Cluster discoveries
V. Krasnoselskikh; M. Balikhin; S. N. Walker; S. Schwartz; D. Sundkvist; V. Lobzin; M. Gedalin; S. D. Bale; F. Mozer; J. Soucek; Y. Hobara; H. Comisel
Space Science Reviews, 178, 2-4, 535-598, Oct. 2013, Peer-reviwed, The physics of collisionless shocks is a very broad topic which has been studied for more than five decades. However, there are a number of important issues which remain unresolved. The energy repartition amongst particle populations in quasiperpendicular shocks is a multi-scale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. The most important processes take place in the close vicinity of the major magnetic transition or ramp region. The distribution of electromagnetic fields in this region determines the characteristics of ion reflection and thus defines the conditions for ion heating and energy dissipation for supercritical shocks and also the region where an important part of electron heating takes place. In other words, the ramp region determines the main characteristics of energy repartition. All these processes are crucially dependent upon the characteristic spatial scales of the ramp and foot region provided that the shock is stationary. The process of shock formation consists of the steepening of a large amplitude nonlinear wave. At some point in its evolution the steepening is arrested by processes occurring within the shock transition. From the earliest studies of collisionless shocks these processes were identified as nonlinearity, dissipation, and dispersion. Their relative role determines the scales of electric and magnetic fields, and so control the characteristics of processes such as ion reflection, electron heating and particle acceleration. The determination of the scales of the electric and magnetic field is one of the key issues in the physics of collisionless shocks. Moreover, it is well known that under certain conditions shocks manifest a nonstationary dynamic behaviour called reformation. It was suggested that the transition from stationary to nonstationary quasiperiodic dynamics is related to gradients, e.g. scales of the ramp region and its associated whistler waves that form a precursor wave train. This implies that the ramp region should be considered as the source of these waves. All these questions have been studied making use observations from the Cluster satellites. The Cluster project continues to provide a unique viewpoint from which to study the scales of shocks. During its lifetime the inter-satellite distance between the Cluster satellites has varied from 100 km to 10000 km allowing scientists to use the data best adapted for the given scientific objective. The purpose of this review is to address a subset of unresolved problems in collisionless shock physics from experimental point of view making use multi-point observations onboard Cluster satellites. The problems we address are determination of scales of fields and of a scale of electron heating, identification of energy source of precursor wave train, an estimate of the role of anomalous resistivity in energy dissipation process by means of measuring short scale wave fields, and direct observation of reformation process during one single shock front crossing. © 2013 Springer Science+Business Media Dordrecht.
Scientific journal, English

The lower ionospheric perturbation as a precursor to the 11 March 2011 Japan earthquake
M. Hayakawa; A. Rozhnoi; M. Solovieva; Y. Hobara; K. Ohta; A. Schekotov; E. Fedorov
GEOMATICS NATURAL HAZARDS & RISK, TAYLOR & FRANCIS LTD, 4, 3, 275-287, Sep. 2013, Peer-reviwed, It is found that clear lower ionospheric perturbations appeared as a precursor to the 11 March 2011 Japan earthquake. This study is based on the observation of two completely different phenomena: (1) subionospheric very low frequency/low frequency propagation anomaly on the NLK (Seattle, USA)-Chofu propagation path, and (2) depression of magnetospheric ultra low frequency emissions observed on the ground (Kakioka, etc.). But, both effects are suggested to be interpreted by a unified phenomenon of seismo-lower ionospheric perturbation because they occurred on the days of 5 and 6 March, 2011.
Scientific journal, English

Surface displacements from GPS and subionospheric VLF signal perturbations related to major earthquakes over Japan
Y. Hobara; G. Suzuki; C; Chieh-Hung; M. Hayakawa
2013 Asia-Pacific radio sceinece conference, **, Sep. 2013, Peer-reviwed
International conference proceedings, English

Charge moment changes of lightning strokes deduced by ELF Network observations in Japan
Y. Hobara; T. Inoue; R. Nakamura; M. Hayakawa; K. Shiokawa
2013 Asia-Pacific radio sceinece conference, **, Sep. 2013, Peer-reviwed
International conference proceedings, English

The Ionospheric Precursor to the 2011 March 11 Earthquake Based upon Observations Obtained from the Japan-Pacific Subionospheric VLF/LF Network
Masashi Hayakawa; Yasuhide Hobara; Alexander Rozhnoi; Maria Solovieva; Kenji Ohta; Jun Izutsu; Tohru Nakamura; Yasushi Kasahara
TERRESTRIAL ATMOSPHERIC AND OCEANIC SCIENCES, CHINESE GEOSCIENCE UNION, 24, 3, 393-408, Jun. 2013, Peer-reviwed, By using network observation of subionospheric VLF (very low frequency)/LF (low frequency) signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 March 11 Japan earthquake (EQ) which occurred at sea proximate to the Tohoku area on the main island (Honshu) of Japan was an exceptionally huge plate-type EQ. A remarkable anomaly (with a decrease in the nighttime amplitude and also with enhancement in dispersion) was detected on March 5 and 6 along the propagation path from the NLK (Seattle, USA) transmitter to Chofu (together with Kochi and Kasugai). We also have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 along the path from JJI (Miyazaki, Kyushu) to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability. (1) How abnormal is this VLF/LF propagation anomaly? (2) What was the temporal evolution of terminator times? (3) Were there any solar-terrestrial effects (especially the effect from geomagnetic storms) on the VLF/LF propagation anomaly? (4) The effect of any other EQs and foreshock activities on the VLF/LF anomaly? (5) Were there any correlations with other related phenomena? Finally, (6) are there any other examples of a VLF/LF propagation anomaly for oceanic EQs? We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly discussed.
Scientific journal, English

Simultaneous observations of surface displacements from GPS and ionospheric perturbations from VLF transmitter signals around major seismic events in Japan
Y. hobara; G. Suzuki; C. C. Hung; M. Hayakawa
EGU General Assembly 2013, **, Apr. 2013, Peer-reviwed
International conference proceedings, English

Nadir Observations of Lightning and TLEs by JEM-GLIMS
M. Sato; T. Ushio; T. Morimoto; M. Suzuki; A. Yamazaki; M. Kikuchi; Y. Takahashi; I. Umran; L. Ivan; Y. Hobara
EGU General Assembly 2013, --, Apr. 2013, Peer-reviwed
International conference proceedings, English

Nadir Observations of Lightning and TLEs by JEM-GLIMS
M. Sato; T. Ushio; T. Morimoto; M. Suzuki; A. Yamazaki; M. Kikuchi; Y. Takahashi; I. Umran; L. Ivan; Y. Hobara
EGU General Assembly 2013, --, Apr. 2013, Peer-reviwed
International conference proceedings, English

Worldwide detection of elf transient associated with the gamma flare of December 27, 2004
A. Yu Schekotov; A. P. Nickolaenko; M. Hayakawa; Y. Hobara; G. Satori; J. Bor; M. Neska
Telecommunications and Radio Engineering (English translation of Elektrosvyaz and Radiotekhnika), 72, 18, 1695-1718, 2013, Peer-reviwed, We present experimental records containing extremely low frequency (ELF) pulses associated with the gamma ray flare of December 27, 2004. The GPS synchronized records were collected at observatories Moshiri (geographic coordinates 44.37 N
142.24 E), Onagawa (38.43 N
141.48 E), Esrange (67.83 N
21.1 E), Karimshino (52.83 N
158.13 E), Nagycenk (47.6 N
16.7 E), and Hornsund (77.0N
15.5E). Data demonstrate an exceptional similarity and contain characteristic pulses around the occurrence time of gamma flare. Our signal processing showed that in addition to fitting the arrival time of gamma rays, the following model predictions were confirmed: radio pulses contain the lowest Schumann resonance mode, the source polarity was positive, the magnetic field tends to be linearly polarized, and the source bearings correspond to the direction toward the sub-flare point. These properties are in accordance with the concept of a parametric electromagnetic pulse originating from a sizeable modification of the global electric circuit by the cosmic gamma flare. © 2013 by Begell House, Inc.
Scientific journal, English

Observation of surface displacements from GPS analyses before and after the Jiashian earthquake (M=6.4) in Taiwan
Chieh-Hung Chen; Strong Wen; Ta-Kang Yeh; Chung-Ho Wang; Horng-Yuan Yen; Jann-Yenq Liu; Yasuhide Hobara; Peng Han
JOURNAL OF ASIAN EARTH SCIENCES, PERGAMON-ELSEVIER SCIENCE LTD, 62, 662-671, Jan. 2013, Peer-reviwed, A blind thrust fault with a unique strike, which is orthogonal to the strike of most tectonic structures in Taiwan, triggered the Jiashian earthquake on March 4, 2010 (M = 6.4; 22.96 degrees N, 120.70 degrees E). This study utilizes 100 global positioning system stations to examine changes of surface displacements during the Jiashian earthquake. We mitigate effects of short-term noise and long-term plate movements from surface displacement data using a frequency dependent filter via the Hilbert-Huang transform and compute the horizontal azimuth (i.e. GPS-azimuth) using residual data at the NS component relative to residual data at the EW component Analytical results show that orientations of horizontal azimuths were aligned and orthogonal to the strike of the blind thrust fault. Meanwhile, inverse orientations are observed before and after the earthquake that agrees well with the seismic rebound theory. As stress disturbed on strata a few days before the earthquake, an impeded region can be clearly identified by disordered orientations of horizontal azimuths for anticipating the mainshock. These results provide an additional view to explore stress disturbance associated with earthquakes and offer more information to examine diverse models of tectonic evolution in this region. (C) 2012 Elsevier Ltd. All rights reserved.
Scientific journal, English

A note on the correlation of seismo-ionospheric perturbations with ground motions as deduced from F-net seismic obsevations
T. Endo; Y. Kasahara; Y. Hobara; T. Sue; M.Hayakawa
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 33, 1, 69-76, Jan. 2013, Peer-reviwed, The purpose of this paper is to try to find any correlation between the ionospheric perturbation as detected by subionospheric VLF/LF propagation and ground motions as detected by wideband seismic observations (so-called F-net). Two huge earthquakes are chosen for our analysis; (1) Niigata-chuetsu-oki earthquake on July 16, 2007 and (2) Iwate-nairiku-nambu earthquake on June 13, 2008. The AW(acoustic wave, period=1-10 min) and AGW(atmospheric gravity wave, period=10-100 min) components in the ground motions are compared with the ionospheric perturbation. It is found that the ground motions in the AGW and AW ranges are enhanced as compared with the backgrounds when the lower ionosphere is perturbed, which might be a possible source of ionospheric perturbation. Though the number of events is only two, this correlation may lend a support to the atmospheric oscillation hypothesis of the lithosphereionosphere coupling due to some precursory ground effect.
Scientific journal, English

Observation of surface displacements from GPS analyses before and after the Jiashian earthquake (M=6.4) in Taiwan
Chieh-Hung Chen; Strong Wen; Ta-Kang Yeh; Chung-Ho Wang; Horng-Yuan Yen; Jann-Yenq Liu; Yasuhide Hobara; Peng Han
JOURNAL OF ASIAN EARTH SCIENCES, PERGAMON-ELSEVIER SCIENCE LTD, 62, 662-671, Jan. 2013, Peer-reviwed, A blind thrust fault with a unique strike, which is orthogonal to the strike of most tectonic structures in Taiwan, triggered the Jiashian earthquake on March 4, 2010 (M = 6.4; 22.96 degrees N, 120.70 degrees E). This study utilizes 100 global positioning system stations to examine changes of surface displacements during the Jiashian earthquake. We mitigate effects of short-term noise and long-term plate movements from surface displacement data using a frequency dependent filter via the Hilbert-Huang transform and compute the horizontal azimuth (i.e. GPS-azimuth) using residual data at the NS component relative to residual data at the EW component Analytical results show that orientations of horizontal azimuths were aligned and orthogonal to the strike of the blind thrust fault. Meanwhile, inverse orientations are observed before and after the earthquake that agrees well with the seismic rebound theory. As stress disturbed on strata a few days before the earthquake, an impeded region can be clearly identified by disordered orientations of horizontal azimuths for anticipating the mainshock. These results provide an additional view to explore stress disturbance associated with earthquakes and offer more information to examine diverse models of tectonic evolution in this region. (C) 2012 Elsevier Ltd. All rights reserved.
Scientific journal, English

Deducing locations and charge moment changes of lightning discharges by ELF network observations in Japan
Yasuhide Hobara; Takahiro Inoue; Masashi Hayakawa; Kazuo Shiokawa
IEEJ Transactions on Power and Energy, 133, 12, 994-1000, 2013, Peer-reviwed, The electromagnetic radiations from lightning discharges have been intensively studied for a long time in different frequency ranges. Recent observations of electromagnetic radiations from lightning in the ELF (extremely low frequency) frequency range so-called ELF transients are recognized as a powerful tool to obtain one of the most important properties of lightning discharges
the charge moment changes (Qds). In this paper we demonstrate the spatio-temporal distributions of lightning discharges together with their charge moment change (CMC) around Japan by using our newly developed domestic ELF observation network. This is the first time to obtain such type of distribution by using only ELF observations in the spatial scale of Japan (a few thousands km). We found that the obtained lightning source distributions both over the Pacific Ocean and the Sea of Japan are originated from the thunderstorm active regions confirmed by other measurements such as WWLLN. Statistical properties of the charge moment changes indicate that both number and CMC of positive CGs are superior to those of negative CGs. Moreover considerably large CMC with both polarities are identified for the CGs over the Pacific Ocean as well as those with positive polarity over the Sea of Japan. © 2013 The Institute of Electrical Engineers of Japan.
Scientific journal, English

Ionospheric perturbations observed by the low altitude satellite DEMETER and possible relation with seismicity
Y.Hobara; R.Nakamura; M.Suzuki; M.Hayakawa; M.Parrot
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 33, 1, 21-29, 2013, Peer-reviwed, The high-altitude ionospheric perturbations around the equatorial anomalies (EA) are often observed by DEMETER spacecraft on the nighttime orbits. The ionospheric perturbations are recognized as an enhancement of the electric field in the ELF frequency range in the satellite coordinate. Clear perturbations are mostly recognized on the dayside of the satellite orbit and the peak perturbation intensity tends to increase with increasing magnetic latitude based on around 1000 perturbation events observed in the year of 2005. The perturbation intensities are examined in relation with major seismic activities. As a result, most importantly higher perturbation intensity persists for the time periods around the occurrence days of the land earthquakes rather than those for the sea earthquakes and without major earthquakes nearby. However, the difference of the observed perturbation intensity between above-mentioned three cases are rather small due to relatively large variability indicative of the weak correlation of seismicity with the high altitude ionospheric perturbations near EA.
Scientific journal, English

ULF magnetic field depression as a possible precursor to the 2011-3.11 Japan earthquake
A.Schekotov; E.Fedorov; Y.Hobara; M.Hayakawa
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 33, 1, 41-51, 2013, Peer-reviwed, The depression (reduction in amplitude) of ULF magnetic field variations of magnetospheric origin is studied at various distances from the epicenter of the strongest earthquake (EQ) which occurred in Japan on March 11, 2011. For this purpose, we have used the ULF data in Japan observed by fluxgate magnetometers at three places located at distances of ~300 km to ~1300 km from the epicenter of the main shock. The period of data analysis is from December 1, 2010 to May 31, 2011. We have found a sharp increase in depression of the horizontal ULF magnetic field component at the frequency of 0.03 - 0.05 Hz (30-50 mHz) at all of three Japanese observatories (Kakioka, Memambetsu and Kanoya) three days before the first strong foreshock (Mw=7.5) and five days before the main shock (Mw = 9). This peak in depression is found to be several times greater than all previous values, but the depression seems to be most enhanced at Kakioka, the station nearest to the EQ epicenter. So that it is likely that this phenomenon could be a possible precursor to the huge 3.11 EQ.
Scientific journal, English

An evidence on the lithosphere-ionosphere coupling in terms of atmospheric gravity waves on the basis of a combined analysis of surface pressure,ionospheric perturbations and ground-based ULF variations
T. Nakamura; V. Korepanov; Y. Kasahara; Y. Hobara; M. Hayakawa
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 33, 1, 53-68, 2013, Peer-reviwed, One major candidate of lithosphere-atmosphere-ionosphere (LAI) coupling mechanism is through atmospheric oscillations triggered near Earth's surface due to some pre-earthquake (EQ) effect, and this channel has been extensively proved by using meteorological disturbances much more easily treated than pre-EQ effects (Korepanov et al., 2009). In the present paper this channel is challengingly studied, for the first time, for pre-EQ phenomena, and we take a rather strong EQ named Niigata-chuetsu EQ on 23 October, 2004 (with magnitude of 6.8 and with depth of 13 km) for which we already know that the ionospheric perturbation did take place prior to the EQ (Hayakawa et al., 2006). In this paper the LAI coupling has been intensively studied by means of coordinated observational data (surface atmospheric pressure data as an indicator of atmospheric gravity waves (AGWs), our own subionospheric VLF/LF data as a measure of ionospheric perturbations and the ground-based ULF data as a measure to monitor the modulation in the ionospheric dynamic region). The wavelet analyses for these parameters in different spatial regions have all indicated the enhancements of fluctuations in the wave frequency of 10 ~ 100 min (in the frequency range of AGWs). The correlation of wavelet spectra between the atmospheric pressure and VLF/LF amplitude has yielded a high value with the delay of a few hours, while there is nearly no distinct delay of the wavelet spectra between the ionospheric perturbation and the ground-based ULF fluctuation. These observational facts are compared with the theoretical estimation of AGW hypothesis, which may provide a convincing support to the AGW channel of the LAI coupling.
Scientific journal, English

Observation of surface displacements from GPS analyses before and after the Jiashian earthquake (M=6.4) in Taiwan
Chieh-Hung Chen; Strong Wen; Ta-Kang Yeh; Chung-Ho Wang; Horng-Yuan Yen; Jann-Yenq Liu; Yasuhide Hobara; Peng Han
JOURNAL OF ASIAN EARTH SCIENCES, PERGAMON-ELSEVIER SCIENCE LTD, 62, 662-671, Jan. 2013, Peer-reviwed, A blind thrust fault with a unique strike, which is orthogonal to the strike of most tectonic structures in Taiwan, triggered the Jiashian earthquake on March 4, 2010 (M = 6.4; 22.96 degrees N, 120.70 degrees E). This study utilizes 100 global positioning system stations to examine changes of surface displacements during the Jiashian earthquake. We mitigate effects of short-term noise and long-term plate movements from surface displacement data using a frequency dependent filter via the Hilbert-Huang transform and compute the horizontal azimuth (i.e. GPS-azimuth) using residual data at the NS component relative to residual data at the EW component Analytical results show that orientations of horizontal azimuths were aligned and orthogonal to the strike of the blind thrust fault. Meanwhile, inverse orientations are observed before and after the earthquake that agrees well with the seismic rebound theory. As stress disturbed on strata a few days before the earthquake, an impeded region can be clearly identified by disordered orientations of horizontal azimuths for anticipating the mainshock. These results provide an additional view to explore stress disturbance associated with earthquakes and offer more information to examine diverse models of tectonic evolution in this region. (C) 2012 Elsevier Ltd. All rights reserved.
Scientific journal, English

Deducing locations and charge moment changes of lightning discharges by ELF network observations in Japan
Yasuhide Hobara; Takahiro Inoue; Masashi Hayakawa; Kazuo Shiokawa
IEEJ Transactions on Power and Energy, 133, 12, 994-1000, 2013, Peer-reviwed, The electromagnetic radiations from lightning discharges have been intensively studied for a long time in different frequency ranges. Recent observations of electromagnetic radiations from lightning in the ELF (extremely low frequency) frequency range so-called ELF transients are recognized as a powerful tool to obtain one of the most important properties of lightning discharges
the charge moment changes (Qds). In this paper we demonstrate the spatio-temporal distributions of lightning discharges together with their charge moment change (CMC) around Japan by using our newly developed domestic ELF observation network. This is the first time to obtain such type of distribution by using only ELF observations in the spatial scale of Japan (a few thousands km). We found that the obtained lightning source distributions both over the Pacific Ocean and the Sea of Japan are originated from the thunderstorm active regions confirmed by other measurements such as WWLLN. Statistical properties of the charge moment changes indicate that both number and CMC of positive CGs are superior to those of negative CGs. Moreover considerably large CMC with both polarities are identified for the CGs over the Pacific Ocean as well as those with positive polarity over the Sea of Japan. © 2013 The Institute of Electrical Engineers of Japan.
Scientific journal, English

Neural network approach to the prediction of seismic events based on low-frequency signal monitoring of the Kuril-Kamchatka and Japanese regions
Irina Popova; Alexander Rozhnoi; Maria Solovieva; Boris Levin; Masashi Hayakawa; Yasuhide Hobara; Pier Francesco Biagi; Konrad Schwingenschuh
Annals of Geophysics, INGV, 56, 3, *-*, 2013, Peer-reviwed, Very-low-frequency/ low-frequency (VLF/LF) sub-ionospheric radiowave monitoring has been widely used in recent years to analyze earthquake preparatory processes. The connection between earthquakes with M ≥5.5 and nighttime disturbances of signal amplitude and phase has been established. Thus, it is possible to use nighttime anomalies of VLF/LF signals as earthquake precursors. Here, we propose a method for estimation of the VLF/LF signal sensitivity to seismic processes using a neural network approach. We apply the error back-propagation technique based on a three-level perceptron to predict a seismic event. The back-propagation technique involves two main stages to solve the problem
namely, network training, and recognition (the prediction itself). To train a neural network, we first create a so-called 'training set'. The 'teacher' specifies the correspondence between the chosen input and the output data. In the present case, a representative database includes both the LF data received over three years of monitoring at the station in Petropavlovsk-Kamchatsky (2005-2007), and the seismicity parameters of the Kuril-Kamchatka and Japanese regions. At the first stage, the neural network established the relationship between the characteristic features of the LF signal (the mean and dispersion of a phase and an amplitude at nighttime for a few days before a seismic event) and the corresponding level of correlation with a seismic event, or the absence of a seismic event. For the second stage, the trained neural network was applied to predict seismic events from the LF data using twelve time intervals in 2004, 2005, 2006 and 2007. The results of the prediction are discussed. © 2013 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.
Scientific journal, English

Ionospheric perturbations observed by the low altitude satellite DEMETER and possible relation with seismicity
Y. Hobara; R. Nakamura; M. Suzuki; M. Hayakawa; M. Parrot
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 33, 33, 21-29, 2013, Peer-reviwed, The high-altitude ionospheric perturbations around the equatorial anomalies (EA) are often observed by DEMETER spacecraft on the nighttime orbits. The ionospheric perturbations are recognized as an enhancement of the electric field in the ELF frequency range in the satellite coordinate. Clear perturbations are mostly recognized on the dayside of the satellite orbit and the peak perturbation intensity tends to increase with increasing magnetic latitude based on around 1000 perturbation events observed in the year of 2005. The perturbation intensities are examined in relation with major seismic activities. As a result, most importantly higher perturbation intensity persists for the time periods around the occurrence days of the land earthquakes rather than those for the sea earthquakes and without major earthquakes nearby. However, the difference of the observed perturbation intensity between above-mentioned three cases are rather small due to relatively large variability indicative of the weak correlation of seismicity with the high altitude ionospheric perturbations near EA.
Scientific journal, English

ULF magnetic field depression as a possible precursor to the 2011/3.11 Japan earthquake
A. Schekotov; E. Fedorov; Y. Hobara; M. Hayakawa
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 33, 1, 41-51, 2013, Peer-reviwed, The depression (reduction in amplitude) of ULF magnetic field variations of magnetospheric origin is studied at various distances from the epicenter of the strongest earthquake (EQ) which occurred in Japan on March 11, 2011. For this purpose, we have used the ULF data in Japan observed by fluxgate magnetometers at three places located at distances of ~300 km to ~1300 km from the epicenter of the main shock. The period of data analysis is from December 1, 2010 to May 31, 2011. We have found a sharp increase in depression of the horizontal ULF magnetic field component at the frequency of 0.03 - 0.05 Hz (30-50 mHz) at all of three Japanese observatories (Kakioka, Memambetsu and Kanoya) three days before the first strong foreshock (Mw=7.5) and five days before the main shock (Mw = 9). This peak in depression is found to be several times greater than all previous values, but the depression seems to be most enhanced at Kakioka, the station nearest to the EQ epicenter. So that it is likely that this phenomenon could be a possible precursor to the huge 3.11 EQ.
Scientific journal, English

The observation of Doppler shifts of subionospheric LF signal in possible association with earthquakes
M. Hayakawa; Y. Kasahara; T. Endoh; Y. Hobara; S. Asai
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, Sep. 2012, Peer-reviwed, The Doppler-shift observation of LF (f = 60 kHz) subionospheric signal from Saga (Kyushu) (with call sign of JJY) as observed at Chofu (CHF), has been used to investigate the properties of ionospheric perturbations possibly associated with earthquakes(EQs). The period of analysis is seismo-active half a year from January 1, 2009 to June 30, 2009, and six EQs with magnitude greater than 5.0 (in a range from 5.1 to 5.8, which took place within the wave sensitive area of the JJY-CHF path) are dealt with. It is found from the Doppler-shift observation at CHF that the Doppler shifts are really observed and the components in the frequency ranges of AGW (atmospheric gravity wave) and AW (acoustic wave) in the Doppler shifts are clearly enhanced, at least, before each EQ. This observational fact would lend a strong support to the important role of atmospheric oscillation channel in the lithosphere-atmosphere-ionosphere coupling mechanism.
Scientific journal, English

First detection of summer blue jets and starters over Northern Kanto area of Japan: Lightning activity
Tomoyuki Suzuki; Masashi Hayakawa; Yasuhide Hobara; Kenichi Kusunoki
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, A7, Jul. 2012, Peer-reviwed, Numerous summer blue jets and blue starters were observed for the first time over the Northern Kanto area of Japan on 15 August 2008. Sixty jets and starters were observed, and emissions continued intermittently for more than 20 min. Very hig frequency (VHF) and low-frequency (LF) lightning activity and extremely low frequency (ELF) transients associated with these phenomena were analyzed during the 5 s before and after their appearance. We found the following unique characteristics of lightning accompanied by jets/ starters: (1) the interval of emissions was different for jets and starters; (2) the jets were strongly connected with negative cloud-to-ground lightning discharges (-CGs), but starters might have been more affected by intra-cloud discharges (ICs); (3) the number of -CGs and ICs quickly increased just before a jet and showed a significant reduction after the jet; (4) the -CG activities began to decay 0.5 s before a starter, although IC activities were very active +/-1 s of a starter; (5) the charge moment change within +/-1 s of the jets and starters, as calculated from ELF transients associated with CGs, were similar to -200 and similar to -100 C.km, respectively; (6) the lightning discharges with jets/starters are clustered in a limited area of overshooting storm top. These results indicate that the same thunderstorm produced both a jet and a starter. This led us to hypothesize that the emittance of either a jet or starter is dependent on the amount of accumulated positive charge and the electrical activities of the parent storm.
Scientific journal, English

A statistical study of the cross-shock electric potential at low Mach number, quasi-perpendicular bow shock crossings using Cluster data
A. P. Dimmock; M. A. Balikhin; V. V. Krasnoselskikh; S. N. Walker; S. D. Bale; Y. Hobara
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 117, Feb. 2012, Peer-reviwed, The cross-shock electrostatic potential at the front of collision-less shocks plays a key role in the distribution of energy at the shock front. Multipoint measurements such as those provided by the Cluster II mission provide an ideal framework for the study of the cross-shock potential because of their ability to distinguish between temporal and spacial variations at the shock front. We present a statistical study of the cross-shock potential calculated for around 50 crossings of the terrestrial bow shock. The statistical dependency of the normalized (with resect to upstream ion kinetic energy) cross-shock potential (Phi(K)) on the upstream Alfven Mach number is in good agreement with analytical results that predict decrease of Phi(k) with increasing Mach number.
Scientific journal, English

Lightning effects in the mesosphere and ionosphere
M. Hayakawa; Y. Hobara; T. Suzuki
Lightning Electromagnetics, Institution of Engineering and Technology, 611-646, 01 Jan. 2012, Peer-reviwed, This chapter describes luminous phenomena above thunderstorm cloud tops. Three general types of transient luminous events (TLEs) have been so far observed: (1) sprites (red sprites), (2) blue jets (and blue starters) and (3) elves.
In book, English

The effects of lightning on the ionosphere/magnetosphere
Y. Hobara; M. Hayakawa
Lightning Electromagnetics, Institution of Engineering and Technology, 647-685, 01 Jan. 2012, Peer-reviwed, This chapter will deal with the effect of lightning onto the upper atmosphere such as the ionosphere and magnetosphere. There are a few possible effects of lightning on the ionosphere/magnetosphere, but we restrict our attention to the following two phenomena: (1) lightning-induced whistlers and (2) ionospheric Alfven resonators (IARs). The former well-known whistlers are defined generally by signals in the extremely low frequency (ELF) and very low frequency (VLF) bands of causative lightning discharges that travel through the ionospheric/magnetospheric plasma along the Earth’s magnetic field. IARs are characterized by the resonance phenomena in the frequency range below the conventional Schumann resonance. Their morphological characteristics and their interpretation in terms of lightning discharges are presented in this chapter.
In book, English

The ionospheric precursor to the 2011 march 11 earthquake as based on the japan-pacific subionospheric VLF/LF network observation
M. Hayakawa; Y. Hobara; A. Rozhnoi; M. Solovieva; K. Ohta; J. Izutsu; T. Nakamura; Y. Yasuda; H. Yamaguchi; Y. Kasahara
Telecommunications and Radio Engineering (English translation of Elektrosvyaz and Radiotekhnika), 71, 18, 1687-1706, 2012, Peer-reviwed, By using the network observations of sub-ionospheric VLF/LF signals in Japan and Russia, we found a significant ionospheric perturbation prior to the 2011/3/11 Japan earthquake (EQ). A remarkable decrease was detected in the nighttime amplitude and increase in the dispersion on March 5 and 6, on the paths from NLK (Seattle, USA) to Chofu, Kochi and Kasugai. We found also the anomalies in March 1-6 period and minima in the nighttime amplitude on March 3 and 4 on the path JJI (Miyazaki, Kyushu) - Kamchatka, Russia. We describe perturbations and discuss the relevant geophysical environment. Data are compared with perturbations of many inland EQs, and with the spatial scale of similar oceanic Sumatra EQ in 2004. The generation mechanism of ionospheric perturbations is outlined. © 2012 by Begell House, Inc.
Scientific journal, English

ULF magnetic field depression as a possible precursor to the 2011/3.11 Japan earthquake
A. Schekotov; E. Fedorov; Y. Hobara; M. Hayakawa
Telecommunications and Radio Engineering (English translation of Elektrosvyaz and Radiotekhnika), 71, 18, 1707-1718, 2012, Peer-reviwed, The depression (reduction in amplitude) of ULF magnetic field variations of magnetospheric origin is studied at various distances from the epicenter of the strongest earthquake (EQ) which occurred in Japan on March 11, 2011. For this purpose, we have used the ULF data in Japan observed by fluxgate magnetometers at three places located at distances of ~ 300 km to ~ 1300 km from the epicenter of the main shock. The period of data analysis is from December 1, 2010 to May 31, 2011. We have found a sharp increase in depression of the horizontal ULF magnetic field component at the frequency of 0.03 - 0.05 Hz (30-50 mHz) at all of three Japanese observatories (Kakioka, Memambetsu and Kanoya) three days before the first strong foreshock (Mw = 7.5) and five days before the main shock (Mw = 9). This peak in depression is found to be several times greater than all previous values, but the depression seems to be most enhanced at Kakioka, the station nearest to the EQ epicenter. So that it is likely that this phenomenon could be a possible precursor to the huge 3.11 EQ. © 2012 by Begell House, Inc.
Scientific journal, English

The observation of Doppler shifts of subionospheric LF signal in possible association with earthquakes
M. Hayakawa; Y. Kasahara; T. Endoh; Y. Hobara; S. Asai
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 117, 9, 2012, Peer-reviwed, The Doppler-shift observation of LF (f = 60 kHz) subionospheric signal from Saga (Kyushu) (with call sign of JJY) as observed at Chofu (CHF), has been used to investigate the properties of ionospheric perturbations possibly associated with earthquakes(EQs). The period of analysis is seismo-active half a year from January 1, 2009 to June 30, 2009, and six EQs with magnitude greater than 5.0 (in a range from 5.1 to 5.8, which took place within the wave sensitive area of the JJY-CHF path) are dealt with. It is found from the Doppler-shift observation at CHF that the Doppler shifts are really observed and the components in the frequency ranges of AGW (atmospheric gravity wave) and AW (acoustic wave) in the Doppler shifts are clearly enhanced, at least, before each EQ. This observational fact would lend a strong support to the important role of atmospheric oscillation channel in the lithosphere-atmosphere-ionosphere coupling mechanism. ©2012. American Geophysical Union. All Rights Reserved.
Scientific journal, English

A statistical study of the cross-shock electric potential at low Mach number, quasi-perpendicular bow shock crossings using Cluster data
A. P. Dimmock; M. A. Balikhin; V. V. Krasnoselskikh; S. N. Walker; S. D. Bale; Y. Hobara
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 117, 2, 2012, Peer-reviwed, The cross-shock electrostatic potential at the front of collision-less shocks plays a key role in the distribution of energy at the shock front. Multipoint measurements such as those provided by the Cluster II mission provide an ideal framework for the study of the cross-shock potential because of their ability to distinguish between temporal and spacial variations at the shock front. We present a statistical study of the cross-shock potential calculated for around 50 crossings of the terrestrial bow shock. The statistical dependency of the normalized (with resect to upstream ion kinetic energy) cross-shock potential (K) on the upstream Alfvén Mach number is in good agreement with analytical results that predict decrease of k with increasing Mach number. Copyright 2012 by the American Geophysical Union.
Scientific journal, English

Possible precursor to the March 11, 2011, Japan earthquake: ionospheric perturbations as seen by subionospheric very low frequency/low frequency propagation
Masashi Hayakawa; Yasuhide Hobara; Yoshihiro Yasuda; Hiroki Yamaguchi; Kenji Ohta; Jun Izutsu; Tohru Nakamura
ANNALS OF GEOPHYSICS, IST NAZIONALE DI GEOFISICA E VULCANOLOGIA, 55, 1, 95-99, 2012, Peer-reviwed, This study reports on a possible very low frequency/low frequency (VLF/LF) subionospheric precursor to a recent earthquake in Japan. As the epicenter of this large Japanese earthquake on March 11, 2011, was located just on the great-circle path from one of our VLF/LF network stations (Chofu) to the NLK US transmitter, we examined the propagation characteristics mainly associated with the signals from the NLK transmitter, as observed at three of the stations in Japan (Chofu, Kasugai and Kochi). On March 5 and 6, 2011, a remarkable anomaly was found on the path from NLK to Chofu, which is highly likely to have been a precursor to this earthquake. The anomaly in the night-time average amplitude at Chofu was characterized by a serious decrease in the signal that exceeded -4 sigma (sigma: standard deviations). The anomaly was found on the same days on the other propagation paths (from NLK to both Kasugai and Kochi), although it was less enhanced. Finally, this propagation anomaly is extensively discussed with respect to the geomagnetic activity, and we also compare this anomaly with the properties related to the former 2004 Sumatra earthquake that had nearly the same magnitude as this March 11, 2011, earthquake.
Scientific journal, English

The effect of a gamma ray flare on Schumann resonances
A. P. Nickolaenko; I. G. Kudintseva; O. Pechony; M. Hayakawa; Y. Hobara; Y. T. Tanaka
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 30, 9, 1321-1329, 2012, Peer-reviwed, We describe the ionospheric modification by the SGR 1806-20 gamma flare (27 December 2004) seen in the global electromagnetic (Schumann) resonance. The gamma rays lowered the ionosphere over the dayside of the globe and modified the Schumann resonance spectra. We present the extremely low frequency (ELF) data monitored at the Moshiri observatory, Japan (44.365A degrees N, 142.24A degrees E). Records are compared with the expected modifications, which facilitate detection of the simultaneous abrupt change in the dynamic resonance pattern of the experimental record. The gamma flare modified the current of the global electric circuit and thus caused the 'parametric' ELF transient. Model results are compared with observations enabling evaluation of changes in the global electric circuit.
Scientific journal, English

Ionospheric perturbations associated with two huge earthquakes in Japan, using principal component analysis for multiple subionospheric VLF/LF propagation paths
Yuya Ono; Yuichi Ida; Yasushi Kasahara; Yasuhide Hobara; Masashi Hayakawa; Alexander Rozhnoi; Maria Solovieva; Oleg A. Molchanov; Kenji Ohta
ANNALS OF GEOPHYSICS, IST NAZIONALE DI GEOFISICA E VULCANOLOGIA, 55, 1, 138-147, 2012, Peer-reviwed, The presence of ionospheric perturbations in possible association with two huge earthquakes (Noto-hanto peninsula and Niigata-chuetu-oki earthquakes) in 2007 was studied on the basis of a conventional statistical study for a particular propagation path from the JJI transmitter in Miyazaki, Kyushu, to Moshiri in Hokkaido. This is based on automatic routine-based signal processing, in which the trend as the average night-time amplitude is significantly decreased, with almost simultaneous significant enhancement in the night-time fluctuation as the night-time integration of negative fluctuation from the average. It is, however, shown that this routine-based signal analysis sometime suffers from artificial (or man-made) effects. Thus, in this study, we propose an additional use of principal component analysis (PCA) for simultaneous observation of a few VLF/LF propagation paths. With the application of this PCA method to multi-path data, the artificial effects can be reasonably removed, and also only the geophysical effects associated with earthquakes are detected, by focusing mainly on the third principal component. The satisfactory separation of the principal components is made possible by pre-analysis of the VLF data (extraction from the raw data of the average over a whole year). This PCA method enables us to identify the seismogenic effects in association with earthquakes with smaller magnitudes, down to M 5.5 or M 5.0.
Scientific journal, English

The Global Lightning and Sprite Measurement (GLIMS) Mission of the International Space Station - Concept and Overview -
Ushio, T; M. Sato; T. Morimoto; M. Suzuki; H. Kikuchi; A. Yamazaki; Y. Takahashi; Y. Hobara; U. Inan; I. Linscott; Y. Sakamoto; R. Ishida; M. Kikuchi; K. Yoshida; Z. Kawasaki
IEEJ Transactions on Fundamentals and Materials, 131, 12, 971-976, Dec. 2011, Peer-reviwed
Scientific journal, English

Ionospheric perturbations associated with the 2011 3.11 EQ, as seen from the subionospheric VLF/LF network
M.Hayakawa; Y. Hobara; A. Rozhnoi; M. Solovieva
Americal Geophysical Union Fall Meeting, NH22A-05, Dec. 2011, Peer-reviwed
International conference proceedings, English

VLF subionospheric disturbances associated with earthquakes: Observations and numerical modeling
Y. Hobara; M. Iwamoto; K. Ohta; M. Hayakawa
Americal Geophysical Union Fall Meeting, NH23A-1550, Dec. 2011, Peer-reviwed
International conference proceedings, English

Universal and local time variations deduced from simultaneous Schumann resonance records at three widely separated observatories
A. P. Nickolaenko; E. I. Yatsevich; A. V. Shvets; M. Hayakawa; Y. Hobara
RADIO SCIENCE, AMER GEOPHYSICAL UNION, 46, RS5003, Sep. 2011, Peer-reviwed, A technique is applied to experimental Schumann resonance intensity that separates the universal (UT) and local time (LT) variations. Two orthogonal horizontal magnetic field components were recorded simultaneously at the observatories of Moshiri, Japan (44.4 degrees N, 142.2 degrees E), Lehta, Russia (64.4 degrees N, 34 degrees E), and West Greenwich, Rhode Island, United States (41.6 degrees N, 71.6 degrees W). We use the cumulative magnetic field power integrated over the first three Schumann resonance modes. Diurnal variations were averaged over a month for the period from August 1999 to December 2001 at each site. These records were combined to obtain estimates for the UT daily patterns of the global thunderstorm activity. Diurnal variations of particular months repeat year after year, indicating that space-time distributions of global thunderstorms are annually replicated with minor deviations. Another technique, based on geometric averaging of records, was used to obtain alternative estimates of the global thunderstorm intensity. Results acquired with both techniques showed an outstanding similarity.
Scientific journal, English

Ionospheric transmission property deduced from lowaltitude satellite and ground-based observations of lightning ELF waves
Y. Hobara; M. Parrot
International Conference on Atmospheric Electricity 2011, -, Aug. 2011, Peer-reviwed
International conference proceedings, English

Ground-based measurement of the seismo-electromagnetic signals
Y. Hobara; M. Hayakawa
URSI General Assembly and Scientific Symposium of International Union of Radio Science, -, Aug. 2011, Peer-reviwed
International conference proceedings, English

SCHUMANN-RESONANCE RECORDS AT THREE OBSERVATORIES AND ULF UNIVERSAL- AND LOCAL-TIME VARIATIONS
A. P. Nickolaenko; E. I. Yatsevich; A. V. Shvets; M. Hayakawa; Y. Hobara
RADIOPHYSICS AND QUANTUM ELECTRONICS, SPRINGER, 53, 12, 706-716, May 2011, Peer-reviwed, We apply a technique separating the universal- and local-time variations in the integrated Schumann-resonance (SR) intensity to the Schumann-resonance data obtained at three observatories, Moshiri (44.365 degrees N, 142.24 degrees E), Lehta (64.427 degrees N, 33.974 degrees E), and West Greenwich (41.6 degrees N, 71.6 degrees W). Feasibility of this technique for joint data of three observatories was proved by model calculations. It is shown that universal-time variations describe intensity variations in the global thunderstorms.
Scientific journal, English

Observation of Doppler shifts of subionospheric VLF/LF signals and the seismic effect
M. Hayakawa; Y. Kasahara; T. Nakamura; Y. Hobara; S. Asai; T. Inaba
European Geosciences Union, -, Apr. 2011, Peer-reviwed
International conference proceedings, English

Statistical property of the ULF magnetic emissions in relation with Izu Island earthquake swarm in Japan
Y. Hobara; T. Kamoi; M. Hayakawa
European Geosciences Union, -, Apr. 2011, Peer-reviwed
International conference proceedings, English

Detection of transient ELF emission caused by the extremely intense cosmic gamma-ray flare of 27 December 2004
Y. T. Tanaka; M. Hayakawa; Y. Hobara; A. P. Nickolaenko; K. Yamashita; M. Sato; Y. Takahashi; T. Terasawa; T. Takahashi
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 38, L08805, Apr. 2011, Peer-reviwed, We report on the first clear detection of transient Extremely-Low-Frequency (ELF) signal caused by an extremely intense cosmic gamma-ray flare. On 2004 December 27, the brightest gamma-ray flare ever recorded was observed by numerous satellites. A transient ELF emission observed at Moshiri and Onagawa in Japan exactly coincided with the peak time of the flare, and its wide pulse width of similar to 40 ms disfavors the possibility of lightning origin. Furthermore, the two horizontal components of ELF magnetic field data recorded at Esrange in Sweden showed clear transient Schumann resonance waveforms. The source direction determined by the Lissajous method roughly corresponds to the subflare point. The chance probability that a sprite occurs within 30 ms of the peak flare time is similar to 0.025%, which again clearly excludes the sprite origin. Thus, a bright cosmic gamma-ray flare is a new source of transient ELF radio signals observed on the Earth, although the emission mechanism needs to be clarified in future. Citation: Tanaka, Y. T., M. Hayakawa, Y. Hobara, A. P. Nickolaenko, K. Yamashita, M. Sato, Y. Takahashi, T. Terasawa, and T. Takahashi (2011), Detection of transient ELF emission caused by the extremely intense cosmic gamma-ray flare of 27 December 2004, Geophys. Res. Lett., 38, L08805, doi: 10.1029/2011GL047008.
Scientific journal, English

Measurement of Doppler shifts of short-distance subionospheric LF transmitter signals and seismic effects
S. Asai; S. Yamamoto; Y. Kasahara; Y. Hobara; T. Inaba; M. Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 116, A2, Feb. 2011, Peer-reviwed, The presence of ionospheric perturbations in possible association with earthquakes (EQs) and their characteristics have been extensively investigated by means of subionospheric VLF/LF propagation. As a possible generation mechanism of those perturbations, we have proposed the atmospheric gravity wave (AGW) (period = 10-100 min) channel as being most plausible on the basis of a lot of indirect evidence including the enhancement of AGW fluctuation in the subionospheric data before an EQ. In order to provide the "direct" support to this hypothesis, we have made, in this paper, the first attempt of observing Doppler shifts of short-distance subionospheric signals from a Japanese LF transmitter JJY (40 kHz) at a few stations in the Tokyo area. As a preliminary analysis, the Doppler shift data from JJY to a station, Machida (distance = 230 km) during five months in 2008 have been analyzed, which has indicated significant enhancements of Doppler shifts in the AGW range for two EQs and a further statistical correlation of Doppler shift in the AGW range with large EQs. Finally the mechanism of lithosphere-atmosphere-ionosphere coupling is discussed.
Scientific journal, English

IMPACT OF A GAMMA-RAY BURST ON THE SCHUMANN RESONANCE
A. P. Nickolaenko; I. G. Kudintseva; O. Pechonaya; M. Hayakawa; T. Nakamura; Ya. Hobara; Ya. Tanaka
RADIOPHYSICS AND QUANTUM ELECTRONICS, SPRINGER, 53, 9-10, 542-556, Feb. 2011, Peer-reviwed, We compare the experimental and simulated data on the impact of an extragalactic gamma-ray burst of December 27, 2004 on the global electromagnetic resonance. It is known from measurements of the signals of ultralong-wave radio stations that the ionizing radiation descended the ionosphere over the dayside hemisphere by 20 km. Such a disturbance should change the eigenfrequencies of the Earth-ionosphere cavity and affect the shape of the observed spectrum of extremely low-frequency Earth's radio noise. The results of observations and modeling of the Schumann-resonance variation under the action of a gamma-ray burst are compared. We employ two models. In the simpler one, the ionospheric disturbance is averaged over the entire globe. The second model allows for the day-night nonuniformity. It is shown that both models yield similar predictions and the effect little depends on the day-night nonuniformity. Since the ionosphere carries the positive electric charge, its vertical displacement causes a current which serves as a "parametric" impulse source of the electromagnetic field. The global size of the source results in that the pulse contains only the lower Schumann-resonance frequency. The extremely low-frequency pulse coincides in time with the gamma-ray burst arrival. The results of observations in the Moshiri observatory (Japan) at the time of a gamma-ray burst, which are compared with the calculation for this observatory are presented. It is shown that both a modification of the Schumann resonance sonogram and a parametric extremely low-frequency radio pulse have been detected in the record.
Scientific journal, English

Measurement of Doppler shifts of short-distance subionospheric LF transmitter signals and seismic effects
S. Asai; S. Yamamoto; Y. Kasahara; Y. Hobara; T. Inaba; M. Hayakawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 116, 2, 2011, Peer-reviwed, The presence of ionospheric perturbations in possible association with earthquakes (EQs) and their characteristics have been extensively investigated by means of subionospheric VLF/LF propagation. As a possible generation mechanism of those perturbations, we have proposed the atmospheric gravity wave (AGW) (period = 10-100 min) channel as being most plausible on the basis of a lot of indirect evidence including the enhancement of AGW fluctuation in the subionospheric data before an EQ. In order to provide the "direct" support to this hypothesis, we have made, in this paper, the first attempt of observing Doppler shifts of short-distance subionospheric signals from a Japanese LF transmitter JJY (40 kHz) at a few stations in the Tokyo area. As a preliminary analysis, the Doppler shift data from JJY to a station, Machida (distance = 230 km) during five months in 2008 have been analyzed, which has indicated significant enhancements of Doppler shifts in the AGW range for two EQs and a further statistical correlation of Doppler shift in the AGW range with large EQs. Finally the mechanism of lithosphere-atmosphere-ionosphere coupling is discussed. Copyright 2011 by the American Geophysical Union.
Scientific journal, English

TLE producing ionospheric disturbances: Observation and numerical modeling
Y. Hobara; M. Iwamoto; K. Ohta; T. Otsuyama; M. Hayakawa
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, -, 2011, Peer-reviwed, This paper reports on the direct comparison between experimental and numerical results of the ionospheric disturbances associated with red sprites in the mesosphere. The ionospheric disturbances due to the sprite ionization column is observed by a continuous monitoring of the amplitude and phase of distant VLF transmitter signals at several locations in Japan, whilst the numerical computation to calculate the spatio-temporal dependence of the observed VLF waves is performed by using a two-dimensional finite-difference time-domain (FDTD) method. As a result, the observed maximum scattered amplitude and phase changes are in close agreement with the numerical results both for carrot and column sprites. The distance variation of the scattered amplitude from the numerical simulation is found to strongly depend on the spatial dimension of the sprite ionization column due to the different scattering mechanisms. The forward scattering amplitude is significantly larger than back scattering amplitude for the carrot sprite indicating the nature of Rayleigh scattering, while both backward and forward scatterings are comparable for a column sprite showing the nature of Mie scattering. © 2011 IEEE.
International conference proceedings, English

Comparison of three methods for the estimation of cross-shock electric potential using Cluster data
A. P. Dimmock; M. A. Balikhin; Y. Hobara
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 29, 5, 815-822, 2011, Peer-reviwed, Cluster four point measurements provide a comprehensive dataset for the separation of temporal and spatial variations, which is crucial for the calculation of the cross shock electrostatic potential using electric field measurements. While Cluster is probably the most suited among present and past spacecraft missions to provide such a separation at the terrestrial bow shock, it is far from ideal for a study of the cross shock potential, since only 2 components of the electric field are measured in the spacecraft spin plane. The present paper is devoted to the comparison of 3 different techniques that can be used to estimate the potential with this limitation. The first technique is the estimate taking only into account the projection of the measured components onto the shock normal. The second uses the ideal MHD condition E . B = 0 to estimate the third electric field component. The last method is based on the structure of the electric field in the Normal Incidence Frame (NIF) for which only the potential component along the shock normal and the motional electric field exist. All 3 approaches are used to estimate the potential for a single crossing of the terrestrial bow shock that took place on the 31 March 2001. Surprisingly all three methods lead to the same order of magnitude for the cross shock potential. It is argued that the third method must lead to more reliable results. The effect of the shock normal inaccuracy is investigated for this particular shock crossing. The resulting electrostatic potential appears too high in comparison with the theoretical results for low Mach number shocks. This shows the variability of the potential, interpreted in the frame of the non-stationary shock model.
Scientific journal, English

Determination of the ionospheric transmission loss of the low frequency EM waves by simultaneous measurements of satellite and ground-based experiments
Y. Hobara; M. Parrot
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, -, 2011, Peer-reviwed, Propagation characteristics of the low frequency electromagnetic waves in the ionosphere are experimentally derived using simultaneous measurements of electromagnetic waves from intensive lightning by French DEMETER satellite and ground-based observations. The transient waveforms generated by worldwide intensive lightning in ELF range are continuously monitored by multi-component measurements in Moshiri, Hokkaido, Japan. Corresponding lightning locations and their electric properties are also derived from the ELF measurement whilst the low altitude satellite (DEMETER) successfully detects electromagnetic pulses over the same lightning sources penetrated through the ionosphere. Direct comparison of ELF transient waves observed by the satellite with the ground experiment gives the unique opportunity to derive the experimental ionospheric property such as an ionospheric transmission loss. The ionospheric transmission loss is obtained for different latitudes and local times by calculating Poynting flux at the lightning and above the ionosphere, and these results are compared with the theoretical calculations by using full-wave numerical method. As a result, the ionospheric penetration loss increases with decreasing the magnetic latitude and with increasing wave frequency. The penetration loss is much larger in daytime rather than night time. The experimentally obtained results are in good agreement with those from theoretical calculations. © 2011 IEEE.
International conference proceedings, English

TLE producing ionospheric disturbances: Observation and numerical modeling
Y. Hobara; M. Iwamoto; K. Ohta; T. Otsuyama; M. Hayakawa
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, -, 2011, Peer-reviwed, This paper reports on the direct comparison between experimental and numerical results of the ionospheric disturbances associated with red sprites in the mesosphere. The ionospheric disturbances due to the sprite ionization column is observed by a continuous monitoring of the amplitude and phase of distant VLF transmitter signals at several locations in Japan, whilst the numerical computation to calculate the spatio-temporal dependence of the observed VLF waves is performed by using a two-dimensional finite-difference time-domain (FDTD) method. As a result, the observed maximum scattered amplitude and phase changes are in close agreement with the numerical results both for carrot and column sprites. The distance variation of the scattered amplitude from the numerical simulation is found to strongly depend on the spatial dimension of the sprite ionization column due to the different scattering mechanisms. The forward scattering amplitude is significantly larger than back scattering amplitude for the carrot sprite indicating the nature of Rayleigh scattering, while both backward and forward scatterings are comparable for a column sprite showing the nature of Mie scattering. © 2011 IEEE.
International conference proceedings, English

Statistical analysis of the ULF magnetic field data during earthquake swarm
Y. Hobara; T. Kamoi; M. Hayakawa
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, -, 2011, Peer-reviwed, In this paper, we intend to extract the statistical properties of seismo-ULF signatures and to address their physical mechanism. The statistical properties (i.e. cumulative probability distribution function) are calculated by using each half-hour period in a number of frequency bands ranging from 1mHz to 2Hz for the time period of about three years around Izu Island earthquake swarm. The statistical analysis has been performed during the year of the swarm, one year before and after the swarm. As a result, the remarkable change in the shape of cumulative probability distribution starts about one month before the swarm particularly at the frequency band of 6.7mHz to 0.01Hz. After the swarm, the statistical distribution returns to the original distribution. For other two years (before and after the swarm), the cumulative probability distribution does not show systematic dependence as is seen for the year of the swarm, which indicates that the observed changes of the distribution is due to the swarm. © 2011 IEEE.
International conference proceedings, English

Ionospheric perturbations in possible association with the 2010 Haiti earthquake, as based on medium-distance subionospheric VLF propagation data
M. Hayakawa; J. P. Raulin; Y. Kasahara; F. C. P. Bertoni; Y. Hobara; W. Guevara-Day
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, COPERNICUS GESELLSCHAFT MBH, 11, 2, 513-518, 2011, Peer-reviwed, Ionospheric perturbations in possible association with the 2010 Haiti earthquake occurred on 12 January 2010 (with a magnitude of 7.0 and depth of 10 km) are investigated on the basis of subionospheric propagation data from the NAA transmitter on the east coast of the USA to a VLF receiving station in Peru. The local nighttime VLF amplitude data are extensively investigated during the period from the beginning of October 2009 to the end of March 2010, in which the trend (nighttime average amplitude), dispersion and nighttime fluctuation are analysed. It is found that a clear precursory ionosphere perturbation is detected just around New Years day of 2010, about 12 days before the main shock, which is characterised by the simultaneous decrease in the trend and the increases in dispersion and nighttime fluctuation. An additional finding might be the presence of the effect of the Earth's tide one and two months before the main shock, which can only be seen for a huge EQ.
Scientific journal, English

Recent studies of Schumann resonance and ELF transients, in “Lightning: Properties, Formation and Types
M. Hayakawa; A. P. Nickolaenko; A. V. Shvets; Y. Hobara
Ed. by M. D. Wood, Nova Sci. Pub., 39-71, 2011, Peer-reviwed
Scientific journal, English

A study on global temperature and thunderstorm activity by using the data of Schumann resonance observed at Nakatsugawa, Japan
Y. Hobara; T. Harada; K. Ohta; M. Sekiguchi; M. Hayakawa
J. Atmos. Electr., 31, 2, 111-119, 2011, Peer-reviwed
Scientific journal, English

Atmospheric gravity waves as a possible candidate for seismo-ionospheric perturbations
M. Hayakawa; Y. Kasahara; T. Nakamura; Y. Hobara; A. Rozhnoi; M. Solovieva; O. A. Molchanov; V. Korepanov
J. Atmos. Electr., 31, 2, 129-140, 2011, Peer-reviwed
Scientific journal, English

Seismogenic effects in the ELF Schumann resonance band
Masashi Hayakawa; Yasuhide Hobara; Kenji Ohta; Jun Izutsu; Alexander P. Nickolaenko; Valery Sorokin
IEEJ Transactions on Fundamentals and Materials, 131, 9, 684-690, 2011, Peer-reviwed, The purpose of this paper is to review the seismogenic effects in the ELF (extremely low frequency) Schumann resonance (SR) band. Two interesting phenomena have been recently observed in this ELF SR band. The first is the enhancement of the SR third or fourth harmonic prior to a large earthquake (EQ), and the second is the excitation of SR-like line emissions possibly related with large EQs. The first phenomenon was initially found as the enhancement of the SR fourth harmonic in Japan, in possible association with the famous 1999 Chi-chi EQ in Taiwan. This was further statistically confirmed on the basis of data during several years and was additionally confirmed by further observations at a different place in Japan. The second SR-like line emissions have been detected in Japan in possible association with two huge EQs in Japan. The frequencies of those line emissions are likely to be shifted from the conventional SR harmonics by a significant amount of 1∼2 Hz, but their temporal variation seems to suggest a close relationship with the conventional SRs. Together with the explanation of the observational evidence of those two phenomena, we provide the plausible theoretical explanation of those phenomena. The first anomaly is interpreted in terms of the wave interference due to the significant difference in propagation length between the direct signal from the American lightning source and that scattered by the seismo-ionospheric perturbations above the epicenters of EQs in Taiwan. The second phenomenon is recently interpreted in terms of the ground detection of gyrotropic waves in the ionospheric dynamo region, being excited by the seismogenic noises from below in the ELF SR band. © 2011 The Institute of Electrical Engineers of Japan.
Scientific journal, English

The ultra-low-frequency magnetic disturbances associated with earthquakes
M. Hayakawa; Y. Hobara; K. Ohta; K. Hattori
Earthquake Science, 24, 6, 523-534, 2011, Peer-reviwed
Scientific journal, English

On the correlation between ionospheric perturbations as detected by subionospheric VLF/LF signals and earthquakes as defined by seismic intensity
M. Hayakawaa; Y. Kasaharaa; T. Nakamuraa; Y. Hobarab; A.Rozhnoic; M. Solovievad; O.A. Molchanov
American Geophysical Union Fall Meeting, -, Dec. 2010, Peer-reviwed
International conference proceedings, English

Variations of the global lightning distribution revealed from three-station Schumann resonance measurements
A. V. Shvets; Y. Hobara; M. Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, Dec. 2010, Peer-reviwed, Schumann resonance (SR) observations performed simultaneously by a global network consisting of three stations (Lekhta (Karelia, Russia), Moshiri (Hokkaido, Japan), and West Greenwich (Rhode Island, United States)) during almost 1 year were used for mapping world thunderstorm activity. A two-stage inverse problem is solved for locating lightning sources distributed over the Earth's surface from the SR background signals. The first stage consists of inversions of the SR magnetic field power spectra to the distributions of lightning intensity by distance relative to an observation point. The obtained distance profiles of intensity of sources are used as tomographic projections for reconstructing a spatial distribution of sources in the second stage. We have suggested the use of source distance profiles obtained from the spectra of outputs of two orthogonal magnetic antennas operating at each observatory as separate tomographic projections. It is shown that the implementation of additional information on the azimuthal distribution of sources, provided by angular selectivity of magnetic sensors, significantly improves the quality of global lightning mapping under the condition of a limited number of observation stations. Maps of the global lightning distributions constructed by the result of inversions of SR spectra show that the most active regions vary zonally on the seasonal time scale and meridionally on the diurnal time scale being connected mainly with continental areas in the tropics.
Scientific journal, English

Statistical study of the quasi-perpendicular shock ramp widths
Y. Hobara; M. Balikhin; V. Krasnoselskikh; M. Gedalin; H. Yamagishi
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, A11, Nov. 2010, Peer-reviwed, The width of the collisionless shock front is one of the key shock parameters. The width of the main shock transition layer is related to the nature of the collisionless process that balances nonlinearity and therefore leads to the formation of the shock itself. The shock width determines how the incoming plasma particles interact with the macroscopic fields within the front and, therefore, the processes that result in the energy redistribution at the front. Cluster and Themis measurements at the quasi-perpendicular part of the terrestrial bow shock are used to study the spatial scale of the magnetic ramp. It is shown that statistically the ramp spatial scale decreases with the increase of the shock Mach number. This decrease of the shock scale together with previously observed whistler packets in the foot of supercritical quasi-perpendicular shock indicates that it is the dispersion that determines the size of magnetic ramp even for supercritical shocks.
Scientific journal, English

Statistical study of the ionospheric turbulence linked to energetic seismic activities observed by DEMETER
Y. Hobara; M. Suzuki; M Hayakawa; M. Parrot
IWSE-AS 2010, -, Nov. 2010, Peer-reviwed
International conference proceedings, English

Interpretation in terms of gyrotropic waves of Schumann-resonance-like line emissions observed at Nakatsugawa in possible association with nearby Japanese earthquakes
M. Hayakawa; K. Ohta; V. M. Sorokin; A. K. Yaschenko; J. Izutsu; Y. Hobara; A. P. Nickolaenko
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 72, 17, 1292-1298, Nov. 2010, Peer-reviwed, The observation of ULF/ELF electromagnetic waves in the frequency range below 50 Hz has been continued at Nakatsugawa (in the Gifu prefecture), Japan since 1998. This paper summarizes anomalous Schumann resonance (SR) phenomena and SR-like line emissions observed at Nakatsugawa in possible association with recent nearby earthquakes (EQs) (the 2004 Mid-Niigata prefecture and the 2007 Noto-Hanto (peninsula) EQs), which have been already described in detail by Ohta etal. (2009). The intensity of particular modes of SR increased before these large EQs and the excitation of other anomalous SR-like line emissions also existed at the frequency shifted by about 2 Hz from the typical SR modes. Since temporal changes of the anomalous SR modes and line emissions are synchronous in time, there might be a possibility that the line emission is a consequence of the anomalous SR. In this paper we propose an interpretation of those anomalous phenomena in terms of excitation of gyrotropic waves due to input wave from below with a band from 15 to 20 Hz as an exciter. The theoretical computational results seem to be generally consistent with the observational finding. (C) 2010 Elsevier Ltd. All rights reserved.
Scientific journal, English

FIRST VERY LOW FREQUENCY DETECTION OF SHORT REPEATED BURSTS FROM MAGNETAR SGR J1550-5418
Y. T. Tanaka; Jean-Pierre Raulin; Fernando C. P. Bertoni; P. R. Fagundes; J. Chau; N. J. Schuch; M. Hayakawa; Y. Hobara; T. Terasawa; T. Takahashi
ASTROPHYSICAL JOURNAL LETTERS, IOP PUBLISHING LTD, 721, 1, L24-L27, Sep. 2010, Peer-reviwed, We report on the first detection of ionospheric disturbances caused by short repeated gamma-ray bursts from the magnetar SGR J1550-5418. Very low frequency (VLF) radio wave data obtained in South America clearly show sudden amplitude and phase changes at the corresponding times of eight soft gamma-ray repeater bursts. Maximum amplitude and phase changes of the VLF signals appear to be correlated with the gamma-ray fluence. On the other hand, VLF recovery timescales do not show any significant correlation with the fluence, possibly suggesting that the bursts' spectra are not similar to each other. In summary, Earth's ionosphere can be used as a very large gamma-ray detector and the VLF observations provide us with a new method to monitor high-energy astrophysical phenomena without interruption such as Earth occultation.
Scientific journal, English

A statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric VLF/LF propagation and earthquakes
M. Hayakawa; Y. Kasahara; T. Nakamura; F. Muto; T. Horie; S. Maekawa; Y. Hobara; A. A. Rozhnoi; M. Solovieva; O. A. Molchanov
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, A9, Sep. 2010, Peer-reviwed, The subionospheric VLF/LF propagation is extensively used to investigate the lower ionospheric perturbation in possible association with earthquakes. An extensive period of data over 7 yr from January 2001 to December 2007 and a combination of different propagation paths in and around Japan are used to examine the statistical correlation between the VLF/LF propagation anomaly (average nighttime amplitude, dispersion, and nighttime fluctuation) and earthquakes with magnitude >6.0. It is then found that the propagation anomaly exceeding the 2s (standard deviation) criterion indicating the presence of ionospheric perturbation is significantly correlated with earthquakes with shallow depth (<40 km). Finally, the mechanism of seismoionospheric perturbations is discussed.
Scientific journal, English

Characteristics of the low frequency EM waves in the ionosphere by simultaneous measurements of DEMETER satellite and ground-based experiment
Y. Hobara; S. Watahiki; M. Hayakawa; M. Parrot
Asia-Pacific Radio Science Conference, -, Sep. 2010, Peer-reviwed
International conference proceedings, English

On the correlation between ionospheric perturbations as detected by subionospheric VLF/LF signals and earthquakes as characterized by seismic intensity
M. Hayakawa; Y. Kasahara; T. Nakamura; Y. Hobara; A. Rozhnoi; M. Solovieva; O. A. Molchanov
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 72, 13, 982-987, Aug. 2010, Peer-reviwed, The long-term data during seven years from January 2001 to December 2007, as observed by the Pacific VLF/LF network consisting of several Japanese stations and one station in Kamchatka, are extensively utilized to perform a statistical correlation study between the lower ionospheric perturbations as detected by subionospheric propagation and earthquakes (EQs). In this paper, we adopt a physical parameter, the maximum seismicity intensity observed (I) to define the strength of an EQ unlike the previously and conventionally used EQ magnitude and depth, which is a combined effect of EQ magnitude and depth, together with the Earth's surface information and geological condition around the EQ epicenter. After considering EQs only take place on the land because of the use of seismicity and by using the superimposed epoch analysis, it is found for the larger EQs with I from 5 to 7 (we feel serious trembling and we expect serious damage) that the most important VLF/LF parameter, trend (nighttime average amplitude), shows a definite decrease about 10 days before the EQ by exceeding 2 sigma (sigma: standard deviation) criterion: the dispersion shows a maximum about 10 days before the EQ but not exceeding 2 sigma line and finally the nighttime fluctuation shows an enhancement about 10 days before the EQ (with exceeding the 2 sigma level). A definite statistical correlation is confirmed between the ionospheric perturbations and I when I is strong enough in a range from 5 to 7. Whereas, there is no significant correlation between the two when I is in a range from 3 to 4. Finally, together with the corresponding results for EQs in the sea, but close to the land, these results are discussed in the light of lithosphere-ionosphere coupling mechanism. (C) 2010 Elsevier Ltd. All rights reserved.
Scientific journal, English

Q-Bursts: Natural ELF Radio Transients
A. P. Nickolaenko; M. Hayakawa; Y. Hobara
SURVEYS IN GEOPHYSICS, SPRINGER, 31, 4, 409-425, Jul. 2010, Peer-reviwed, We overview resonance spectra and present analytical expressions for the waveforms of natural extremely low frequency transient events (Q-bursts). It is shown that model and observed waveforms are similar when a wideband receiver is used at a place with low level of industrial interference. We also describe how to detect a natural ELF transient signal embedded in the man-made noise by using the singular spectral analysis.
Scientific journal, English

A comparison of different source location methods for ELF transients by using the parent lightning discharges with known positions
T. Nakamura; M. Sekiguchi; Y. Hobara; M. Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 115, Jun. 2010, Peer-reviwed, Different kinds of direction finding methods (azimuth and range determinations) have been proposed so far in order to locate ELF transients. As for the azimuth determination, we have used the Lissajous method and goniometer and Poynting vector methods, which are found to be not so much different. The biggest problem is the range (or source-to-observer distance) estimation, which is principally based on the use of wave impedance. By using the known positions of parent lightning discharges during the European sprite campaign, we have compared different methods ((1) cross-correlation over a wide frequency range between the measured and theoretical wave impedances, (2) the use of peak frequency in the observed wave impedance, (3) Jones and Kemp method (the use of maxima and minima in the frequency spectrum of wave impedance), (4) the use of oscillation frequency in the wave impedance variation), and it is found that the best one is the use of Jones and Kemp method with an error of 0.33 Mm for the nine events with sufficient S/N ratio from the analyzed 11 events. This has been based on the FFT analysis. However, for the remaining two events with small time separation, we have tried the use of wavelet analysis, which improved the range determination significantly. Finally, we recommend a combined use of Jones and Kemp method and wavelet analysis for locating ELF transients.
Scientific journal, English

Ionospheric turbulence associated with energetic earthquakes observed by a low-altitude satellite
Y. Hobara; M. Suzuki; M. Hayakawa; M. Parrot
2010 Western Pacific Geophysics Meeting, -, Jun. 2010, Peer-reviwed
International conference proceedings, English

Statistical study of the ionospheric turbulence linked to energetic seismic activities observed by a low-altitude satellite
Y. Hobara; M. Suzuki; M. Hayakawa; M. Parrot
EGU General Assembly, -, May 2010
International conference proceedings, English

Reception of ELF transmitter signals at Moshiri, Japan, and their propagation characteristics
M. Yano; Y. Ida; Y. Hobara; M. Hayakawa; A. P. Nickolaenko
RADIO SCIENCE, AMER GEOPHYSICAL UNION, 45, RS1009, doi: 10, 1029/2009RS004224, Feb. 2010, Peer-reviwed, Measurements are described of 82 Hz radio signals arriving from the Russian ELF transmitter located on the Kola Peninsula, Russia. We used two orthogonal calibrated horizontal magnetic field sensors and a vertical electric antenna at the Moshiri observatory, Hokkaido (geographic coordinates; 44.4 degrees N, 142.2 degrees E). Several propagation characteristics were studied: (1) signal amplitude and its variations on diurnal and seasonal scales, (2) phase difference between the two horizontal magnetic field components (wave polarization), and (3) wave arrival angle. The amplitude detected was compared with early published data, showing a good agreement. We estimated the source current moment of the transmitter by comparing our experimental amplitude with theoretical computations. This 82 Hz signal field is found to be linearly polarized, which allowed for the goniometric finding of source bearing. The arrival azimuth is consistent with the geometry of the experiment.
Scientific journal, English

Variations of the global lightning distribution revealed from three-station Schumann resonance measurements
A. V. Shvets; Y. Hobara; M. Hayakawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 12, 2010, Peer-reviwed, Schumann resonance (SR) observations performed simultaneously by a global network consisting of three stations (Lekhta (Karelia, Russia), Moshiri (Hokkaido, Japan), and West Greenwich (Rhode Island, United States)) during almost 1 year were used for mapping world thunderstorm activity. A two-stage inverse problem is solved for locating lightning sources distributed over the Earth's surface from the SR background signals. The first stage consists of inversions of the SR magnetic field power spectra to the distributions of lightning intensity by distance relative to an observation point. The obtained distance profiles of intensity of sources are used as tomographic projections for reconstructing a spatial distribution of sources in the second stage. We have suggested the use of source distance profiles obtained from the spectra of outputs of two orthogonal magnetic antennas operating at each observatory as separate tomographic projections. It is shown that the implementation of additional information on the azimuthal distribution of sources, provided by angular selectivity of magnetic sensors, significantly improves the quality of global lightning mapping under the condition of a limited number of observation stations. Maps of the global lightning distributions constructed by the result of inversions of SR spectra show that the most active regions vary zonally on the seasonal time scale and meridionally on the diurnal time scale being connected mainly with continental areas in the tropics. Copyright 2010 by the American Geophysical Union.
Scientific journal, English

Statistical study of the quasi-perpendicular shock ramp widths
Y. Hobara; M. Balikhin; V. Krasnoselskikh; M. Gedalin; H. Yamagishi
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 11, 2010, Peer-reviwed, The width of the collisionless shock front is one of the key shock parameters. The width of the main shock transition layer is related to the nature of the collisionless process that balances nonlinearity and therefore leads to the formation of the shock itself. The shock width determines how the incoming plasma particles interact with the macroscopic fields within the front and, therefore, the processes that result in the energy redistribution at the front. Cluster and Themis measurements at the quasi-perpendicular part of the terrestrial bow shock are used to study the spatial scale of the magnetic ramp. It is shown that statistically the ramp spatial scale decreases with the increase of the shock Mach number. This decrease of the shock scale together with previously observed whistler packets in the foot of supercritical quasi-perpendicular shock indicates that it is the dispersion that determines the size of magnetic ramp even for supercritical shocks. Copyright 2010 by the American Geophysical Union.
Scientific journal, English

VLF subionospheric disturbances and ELF transients associated with TLEs: observations and modelling
Y. Hobara; M. Hayakawa; H. Fujii; K. Ohta
PROPAGATION EFFECTS OF VERY LOW FREQUENCY RADIO WAVES, AMER INST PHYSICS, 1286, 158-+, 2010, Peer-reviwed, This paper reports on the direct comparison between experimental and numerical results of the ionospheric perturbation associated with red sprites in the mesosphere. The ionospheric perturbation due to the sprite ionization column is observed by a continuous monitoring of the amplitude and phase of distant VLF transmitter signals at several locations in Japan, whilst the numerical computation to calculate the spatio temporal dependence of the observed VLF waves is performed by using a two-dimensional finite-difference time-domain (FDTD) method. As a result, the observed maximum scattered amplitude and phase changes are in close agreement with the numerical results for a carrot sprite. The distance variation of the scattered amplitude from the numerical simulation is found to strongly depend on the spatial dimension of the sprite ionization column due to the different scattering mechanisms. The forward scattering amplitude is significantly larger than that for back scattering for the carrot sprite indicating the nature of Mie scattering, while both backward and forward scatterings are comparable for a column sprite showing the nature of Rayleigh scattering.
International conference proceedings, English

VLF subionospheric disturbances and ELF transients associated with TLEs: observations and modelling
Y. Hobara; M. Hayakawa; H. Fujii; K. Ohta
PROPAGATION EFFECTS OF VERY LOW FREQUENCY RADIO WAVES, AMER INST PHYSICS, 1286, 158, 158-+, 2010, Peer-reviwed, This paper reports on the direct comparison between experimental and numerical results of the ionospheric perturbation associated with red sprites in the mesosphere. The ionospheric perturbation due to the sprite ionization column is observed by a continuous monitoring of the amplitude and phase of distant VLF transmitter signals at several locations in Japan, whilst the numerical computation to calculate the spatio temporal dependence of the observed VLF waves is performed by using a two-dimensional finite-difference time-domain (FDTD) method. As a result, the observed maximum scattered amplitude and phase changes are in close agreement with the numerical results for a carrot sprite. The distance variation of the scattered amplitude from the numerical simulation is found to strongly depend on the spatial dimension of the sprite ionization column due to the different scattering mechanisms. The forward scattering amplitude is significantly larger than that for back scattering for the carrot sprite indicating the nature of Mie scattering, while both backward and forward scatterings are comparable for a column sprite showing the nature of Rayleigh scattering.
International conference proceedings, English

Acomparison of different source location methods forELFtransients by using the parent lightning discharges with known positions
T. Nakamura; M. Sekiguchi; Y. Hobara; M. Hayakawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 6, -, 2010, Peer-reviwed, Different kinds of direction finding methods (azimuth and range determinations) have been proposed so far in order to locate ELF transients. As for the azimuth determination, we have used the Lissajous method and goniometer and Poynting vector methods, which are found to be not so much different. The biggest problem is the range (or source-to-observer distance) estimation, which is principally based on the use of wave impedance. By using the known positions of parent lightning discharges during the European sprite campaign, we have compared different methods ((1) cross-correlation over a wide frequency range between the measured and theoretical wave impedances, (2) the use of peak frequency in the observed wave impedance, (3) Jones and Kemp method (the use of maxima and minima in the frequency spectrum of wave impedance), (4) the use of oscillation frequency in the wave impedance variation), and it is found that the best one is the use of Jones and Kemp method with an error of 0.33 Mm for the nine events with sufficient S/N ratio from the analyzed 11 events. This has been based on the FFT analysis. However, for the remaining two events with small time separation, we have tried the use of wavelet analysis, which improved the range determination significantly. Finally, we recommend a combined use of Jones and Kemp method and wavelet analysis for locating ELF transients. Copyright © 2010 by the American Geophysical Union.
Scientific journal, English

Ground-based detection of sprites and their parent lightning flashes over Africa during the 2006 AMMA campaign
E. R. Williams; W. A. Lyons; Y. Hobara; V. C. Mushtak; N. Asencio; R. Boldi; J. Bor; S. A. Cummer; E. Greenberg; M. Hayakawa; R. H. Holzworth; V. Kotroni; J. Li; C. Morales; T. E. Nelson; C. Price; B. Russell; M. Sato; G. Satori; K. Shirahata; Y. Takahashi; K. Yamashita
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, WILEY-BLACKWELL, 136, 257-271, Jan. 2010, Peer-reviwed, Sprites have been detected in video camera observations from Niger over mesoscale convective systems in Nigeria during the 2006 AMMA (African Monsoon Multidisciplinary Analysis) campaign The parent lightning flashes have been detected by multiple Extremely Low Frequency (ELF) receiving stations worldwide The recorded charge moments of the patent lightning flashes are often in excellent agreement between different receiving sites, and are furthermore consistent with conventional dielectric breakdown in the mesosphere as the origin of the sprites Analysis of the polarization of the horizontal magnetic field at the distant receivers provides evidence that the departure from linear magnetic polarization at ELF is caused primarily by the clay night asymmetry of the Earth-ionosphere cavity Copyright (C) 2009 Royal Meteorological Society
Scientific journal, English

Subionospheric VLF/LF Probing of Ionospheric Perturbations Associated with Earthquakes: A Possibility of Earthquake Prediction.
M. Hayakawa; T. Horie; F. Muto. Y; Kasahara; K. Ohta; J. Y. Liu; Y. Hobara
SICE JCMSI, The Society of Instrument and Control Engineers, 3, 1, 10-14, 2010, Peer-reviwed, The VLF (Very Low Frequency) / LF (Low Frequency) receiving network has been established in Japan, which is composed of seven observing stations (Moshiri (Hokkaido), Chofu (Tokyo, UEC, University of Electro-Communications), Tateyama (Chiba), Shimizu (Shizuoka), Kasugai (Aichi), Maizuru (Kyoto) and Kochi (Kochi)), and three additional foreign stations have been established in Kamchatka, Taiwan and Indonesia. At each station we observe simultaneously several VLF/LF transmitter signals (two Japanese transmitters with call signals fo JJY (Fukushima), JJI (Miyazaki)), and foreign VLF transmitters (NWC (Western Australia, Australia), NPM (Hawaii, USA), NLK (Washington, USA)). This Japanese VLF/LF network is used to study the ionospheric perturbations associated with earthquakes, and we present two recent results; (1) a statistical result on the correlation between VLF/LF propagation anomalies and earthquakes, and (2) the latest results during the last six months on the two particular propagation paths; JJY-Moshiri and JJY-Taiwan. Then, we discuss the correlation of ionospheric perturbations with earthquakes in the sense of a possibility of earthquake prediction by means of VLF propagation anomalies.
Scientific journal, English

The ionospheric perturbations associated with Asian earthquakes as seen from the subionospheric propagation from NWC to Japanese stations
Y. Kasahara; F. Muto; Y. Hobara; M. Hayakawa
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, COPERNICUS GESELLSCHAFT MBH, 10, 3, 581-588, 2010, Peer-reviwed, Huge five earthquakes with magnitude greater than 6.0 took place in Asia (include Philippines, Indonesia, etc.) during the period from the beginning of August 2008 to the end of Junuary 2009, and the corresponding data of subionospheric VLF propagation between the NWC transmitter (Australia, 19.8 kHz) and a few Japanese stations (distance 6 similar to 8 Mm) are examined. As the result of our analysis by means of (1) trend (average nighttime amplitude), (2) dispersion, (3) nighttime fluctuation, and (4) atmospheric gravity wave enhancement, three earthquakes from the five taking place within the fifth Frenel zone are found to have accompanied a precursory signature in VLF propagation. On the other hand, there were observed no such precursory signatures for the remaing two earthquakes. One is too deep (> 400 km) and another is too distant from the great-circle path. These characteristics of seismo-ionospheric perturbations would be of essential importance in studying the spatial/temporal properties of seismo-ionospheric perturbations for medium-distance propagation.
Scientific journal, English

Fractal analysis of subionospheric LF propagation data and consideration of the lithosphere-atmosphere-ionosphere coupling
T. Imamura; Y. Ida; Y. Kasahara; T. Nakamura; Y. Hobara; M. Hayakawa
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, COPERNICUS GESELLSCHAFT MBH, 10, 4, 901-906, 2010, Peer-reviwed, Fractal analysis has been applied to the local nighttime data of subionospheric LF propagation, and the fractal dimension is estimated every day in the two distinct frequency ranges (AW: acoustic wave and AGW: atmospheric gravity wave). The data during several years are analyzed for the propagation paths from the Japanese transmitter of JJY to Moshiri (Hokkaido) and to Kochi. As the result of analysis, we come to the conclusion that when we pay attention to the period just around the earthquake, we sometimes detect some significant increases in the fractal dimension either in AW or AGW range. This indicates that the self - organization effect prior to an earthquake in the lithosphere, might be seen even in the lower ionosphere, probably in terms of atmospheric oscillation effect.
Scientific journal, English

Current status of seismo-electromagnetics for short-term earthquake prediction
Masashi Hayakawa; Yasuhide Hobara
GEOMATICS NATURAL HAZARDS & RISK, TAYLOR & FRANCIS LTD, 1, 2, 115-155, 2010, Peer-reviwed, Short-term (timescale of hours, days and weeks) earthquake (EQ) prediction is of essential importance to mitigate EQ disasters. Short-term EQ prediction has so far been based on seismic measurements (i.e. mechanical observation of crustal movements), but it was concluded in Japan about 10 years ago that EQ prediction is impossible by means of the mechanical method. Hence, there has been an increased interest and a lot of progress in non-seismic measurement during the last decade. A new approach was developed where electromagnetic measurements provide microscopic information on the lithosphere. The present paper is intended to give a history of short-term EQ prediction, and also we hope that this paper reviews the current status of a new science field, 'seismo-electromagnetics'. We make a general review of different phenomena taking place in the lithosphere, atmosphere and the ionosphere, but we pay more attention to the subjects of our preference including lithospheric ultra low frequency (ULF) electromagnetic emissions, and seismo-ionospheric perturbations.
Scientific journal, English

A statistical study on the AGW modulations in subionospheric VLF/LF propagation data and consideration of the generation mechanism of seismo-ionospheric perturbations
Y. Kasahara; T. Nakamura; Y. Hobara; M. Hayakawa; A. Rozhnoi; M. Solovieva; O.A. Molchanov
J. Atmos. Electr., Society of Atmospheric Electricity of Japan, 30, 2, 103-112, 2010, Peer-reviwed, Though there have been several papers suggesting the important role of atmospheric gravity waves (AGWs) in the generation mechanism of seismo-ionospheric perturbations, no reports have appeared on the statistical study of the AGW effect. Based on the data over nine years and for many propagation paths in and around Japan, this paper presents the first statistical result on the role of AGW in seismo-ionospheric effects. The conclusion by means of superimposed epoch analysis is that the AGW modulation (fluctuation) is rather enhanced about 10 days only for shallow (depth ‹ 40km) earthquakes, but its significance level is just close to the conventional 2σ (σ : standard deviation) level. So that, we can conceive that the AGW channel is the most dominant hypothesis for seismo- ionospheric perturbations, but an alternative channel such as chemical (+ electric field) channel is also operative either simultaneously for an EQ or may be dominant for a small number of earthquakes.
Scientific journal, English

地球周辺での電磁ノイズの計測と地球環境の監視
早川正士; 芳原容英
電子情報通信学会 論文誌B, 93-B, 11, 1495-1503, 2010, Peer-reviwed
Scientific journal, Japanese

A statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric VLF/LF propagation and earthquakes
M. Hayakawa; Y. Kasahara; T. Nakamura; F. Muto; T. Horie; S. Maekawa; Y. Hobara; A. A. Rozhnoi; M. Solovieva; O. A. Molchanov
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 115, 9, -, 2010, Peer-reviwed, The subionospheric VLF/LF propagation is extensively used to investigate the lower ionospheric perturbation in possible association with earthquakes. An extensive period of data over 7 yr from January 2001 to December 2007 and a combination of different propagation paths in and around Japan are used to examine the statistical correlation between the VLF/LF propagation anomaly (average nighttime amplitude, dispersion, and nighttime fluctuation) and earthquakes with magnitude >
6.0. It is then found that the propagation anomaly exceeding the 2 (standard deviation) criterion indicating the presence of ionospheric perturbation is significantly correlated with earthquakes with shallow depth (<
40 km). Finally, the mechanism of seismoionospheric perturbations is discussed. © Copyright 2010 by the American Geophysical Union.
Scientific journal, English

A study of the morphology of winter sprites in the Hokuriku area of Japan in relation to cloud charge height
K. Myokei; Y. Matsudo; T. Asano; T. Suzuki; Y. Hobara; K. Michimoto; M. Hayakawa
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 71, 5, 597-602, Apr. 2009, Peer-reviwed, Continuous observations of sprites in the Hokuriku area of Japan were performed from two optical sites during the three winter periods. The purpose of this observation is to study the major effect in the appearance of sprites and in determining the morphology of sprites (columns or carrots). Detailed analysis is performed based on the estimation of the height of -10 degrees C at the time of sprite occurrence. When the height of -10 degrees C is lower than 1800m, the occurrence of sprites is infrequent, and the dominant shape is column. Then when it is increased (1800-3000 m), a new situation takes place, namely the occurrence of sprites is very enhanced and more spectacular shapes like carrots tend to be frequently observed in addition to column sprites. These sprite characteristics are first compared with those of parent lightning in the Hokuriku area and with our latest computer simulations on sprite initiation. (C) 2009 Elsevier Ltd. All rights reserved.
Scientific journal, English

Further study on the role of atmospheric gravity waves on the seismo-ionospheric perturbations as detected by subionospheric VLF/LF propagation
F. Muto; Y. Kasahara; Y. Hobara; M. Hayakawa; A. Rozhnoi; M. Solovieva; O. A. Molchanov
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, COPERNICUS GESELLSCHAFT MBH, 9, 4, 1111-1118, 2009, Peer-reviwed, As the target earthquake we have taken a huge earthquake (EQ) named Miyagi-oki earthquake on 16 August 2005 (with magnitude of 7.2) and we have analyzed the 4 month period including the date of this EQ. In addition to our previous analysis on the nighttime average amplitude (trend) and nighttime fluctuation, we have proposed the use of fluctuation power spectra in the frequency rage of atmospheric gravity waves (period=10 min to 100 min) as a third parameter of subionospheric VLF/LF propagation characteristics. Then it is found that this third parameter would be of additional importance in confirming the presence of seismoionospheric perturbations. Finally, we have discovered an important role of lunar tidal effect in the VLF/LF data, which appears one and two months before this large EQ.
Scientific journal, English

Morphology of winter sprites in the Hokuriku area of Japan: Monthly variation and dependence on air temperature
K. Myokei; Y. Matsudo; T. Asano; M. Sekiguchi; T. Suzuki; Y. Hobara; M. Hayakawa
J. Atmos. Electr., 29, 1, 23-34, 2009, Peer-reviwed
Scientific journal, English

Sprites over Africa during the AMMA with Multiple Electromagnetic Detections of Their Parent Lightning Flashes
Y. Hobara; K. Shirahata; E. Williams; V. Mushtak; W. Lyons; the AMMA ELF Team
EGU General Assembly, -, 2009, Peer-reviwed
International conference proceedings, English

Simultaneous measurements of lightning-generated ELF waves by low-altitude satellite and ground-based experiment
Y. Hobara; T. Uchida; T. Nakamura; M. Hayakawa; M. Parrot
EGU General Assembly, -, 2009, Peer-reviwed
International conference proceedings, English

Global distribution and characteristics of intense lightning discharges as deduced from ELF transients observed at Moshiri (Japan)
K. Yamashita; T. Otsuyama; Y. Hobara; M. Sekiguchi; Y. Matsudo; M. Hayakawa; V. Korepanov
J. Atmos. Electr., 29, 71-80, 2009, Peer-reviwed
Scientific journal, English

Comparison of the variations in the intensity of global electromagnetic resonance and ground surface temperature
A. P. Nickolaenko; M. Hayakawa; M. Sekiguchi; Y. Hobara
RADIOPHYSICS AND QUANTUM ELECTRONICS, SPRINGER, 51, 12, 931-945, Dec. 2008, Peer-reviwed, We compare the dynamics of the intensity of the global electromagnetic (Schumann) resonance monitored in Japan with the global ground surface temperature (GST) over the period from November 1998 to May 2002. It is shown that the Schumann resonance (SR) intensity varies coherently with the ground surface temperature at mid-latitudes: the relevant cross-correlation coefficient exceeds 0.8. The linear correlation of data decreases with a decreasing latitude interval. We applied the principal component analysis (PCA) to distinguish inter-annual trends (anomalies) in the records from the periodic annual and semi-annual variations. The annual component of the SR intensity behaves similarly to the mid-latitude GST, while the inter-annual variations in the electromagnetic data are similar to those of the GST in the tropics. The regression analysis allowed us to obtain the analytical expressions relating the SR intensity with both the mid-latitude and low-latitude GST. Application of these equations allowed us to retrieve the observed SR pattern from the ground surface temperature and to "reconstruct" the variations in the tropical GST from recorded SR intensity.
Scientific journal, English

Cluster observations of electrostatic solitary waves near the Earth's bow shock
Y. Hobara; S. N. Walker; M. Balikhin; O. A. Pokhotelov; M. Gedalin; V. Krasnoselskikh; M. Hayakawa; M. Andre; M. Dunlop; H. Reme; A. Fazakerley
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 113, A5, May 2008, Peer-reviwed, Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wave structures such as wave propagation vector, propagation velocity, scale-size and potential amplitude. Two classes of waves are observed. Bipolar solitary waves typically propagate in the solar wind direction toward the shock but at a significant angle from the ambient magnetic field. Unipolar/tripolar solitary waves tend to propagate along the ambient magnetic field. The wave amplitude-scale size relation is similar to that obtained for similar structures observed in the auroral zone. The structures lie in the theoretically allowed region in width-amplitude space to be consistent with the BGK ion holes. Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wave structures such as wave propagation vector, propagation velocity, scale-size and potential amplitude. Two classes of waves are observed. Bipolar solitary waves typically propagate in the solar wind direction toward the shock but at a significant angle to the ambient magnetic field in contrast to most previous studies which assume parallel propagation to the ambient magnetic field. In contrast, unipolar/tripolar solitary waves tend to propagate along the ambient magnetic field. The wave amplitude-scale size relation is similar to that obtained for structures observed in the auroral zone. The structures lie in the theoretically allowed region in width-amplitude space to be consistent with the BGK (Bernstein-Greene-Kruskal) ion holes. The two classes of observed solitary waves may greatly influence the ambient plasma dynamics around the shock. The bipolar solitary waves do not exhibit a large net potential difference but may still play an important role in plasma thermalisation by particle scattering. Unipolar/tripolar solitary waves exhibit a remarkable net potential difference that may be responsible for the plasma energisation along the ambient magnetic field.
Scientific journal, English

Nonlinear dynamics of foreshock structures: Application of nonlinear autoregressive moving average with exogenous inputs model to Cluster data
D. Zhu; M. A. Balikhin; M. Gedalin; H. Alleyne; S. A. Billings; Y. Hobara; V. Krasnosel'skikh; M. W. Dunlop; M. Ruderman
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 113, A4, Apr. 2008, Peer-reviwed, Nonlinear processes identification techniques based on multi-input nonlinear autoregressive moving average with exogenous inputs model has been applied to four-point Cluster measurements in order to study nonlinear processes that take place in the terrestrial foreshock. It is shown that both quadratic and cubic processes are involved in the evolution of shocklets in particular in the steepening of their leading edge and generation of whistler precursor. Nonlinear processes do not play an essential role in the dynamics and propagation of small-amplitude whistler packets. However, for large-amplitude wave packets, cubic processes lead to the considerable modification of apparent propagation velocity.
Scientific journal, English

Lower hybrid waves at the shock front: a reassessment
S. N. Walker; M. A. Balikhin; H. St. C. K. Alleyne; Y. Hobara; M. Andre; M. W. Dunlop
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 26, 3, 699-707, 2008, Peer-reviwed, The primary process occur-ring at a collisionless shock is the redistribution of the bulk upstream energy into other degrees of freedom. One part of this process results in the acceleration of electrons at the shock front. Accelerated electrons are observed at the terrestrial and other planetary shocks, comets, and their effects are observed in astrophysical phenomena such as supernova remnants and jets in the form of X-ray bremsstrahlung radiation. One of the physical models for electron acceleration at supercritical shocks is based on low-hybrid turbulence due to the presence of reflected ions in the foot region. Since lower hybrid waves propagate almost perpendicular to the magnetic field they can be simultaneously in resonance with both the unmagnetised ions (omega=V(i)k(perpendicular to)) and magnetised electrons (omega=V(e)k(parallel to)). In this paper, Cluster observations of the electric field are used to study the occurrence of lower hybrid waves in the front of the terrestrial bow shock. It is shown that the lower hybrid waves exist as isolated wave packets. However, the very low level of the observed lower hybrid turbulence is too small to impart significant energisation to the electron population.
Scientific journal, English

Optical and radio probing of lightning-associated phenomena in the atmosphere and ionosphere
T. Asano; Y. Matsudo; T. Suzuki; Y. Hobara; M. Hayakawa
2008 PROCEEDINGS OF SICE ANNUAL CONFERENCE, VOLS 1-7, IEEE, 1604-+, 2008, Peer-reviwed, The monitoring and/or sounding of lightning discharges and their associated phenomea (mesospheric optical emissions etc.) has been performed by radio and optical measurements. We pay attention to the winter lightning in the Hokuriku area (Japan Sea side) of Japan, because it is extremely important to investigate whether lighting discharges in the Hokuriku. area (whole spatial scale is relatively small in comparison with the conventional summer lightning in the US) could trigger the mesospheric optical emissions. The optical observation of those mesospheric emissions and the corresponding radio sounding by ELF and VHF radio waves of their parent lightning, have been reported. observing systems are firstly presented, and our latest observational facts on the mesospheric emissions in the Hokuriku area, their parent lightning and some computer simulations on the sprite initiation, are presented.
International conference proceedings, English

Diurnal and seasonal variations in the Schumann resonance parameters at Moshiri
M. Sekiguchi; Y. Hobara; M. Hayakawa
J. Atmos. Electr., 28, 1, 1-10, 2008, Peer-reviwed
Scientific journal, English

Mode identification of terrestrial ULF waves observed by Cluster: A case study
Y. Hobara; S. N. Walker; M. Dunlop; M. Balikhin; O. A. Pokhotelov; H. Nilsson; H. Reme
PLANETARY AND SPACE SCIENCE, PERGAMON-ELSEVIER SCIENCE LTD, 55, 15, 2257-2260, Dec. 2007, Peer-reviwed, Using multipoint measurements from the Cluster mission wave identification techniques are applied to observations of ULF waves made in the terrestrial foreshock with the aim of identifying the modes and properties of the waves taking into account the effects of a high beta plasma. The wave properties in the spacecraft and plasma rest frames are experimentally derived using minimum variance analysis. Two waves with periods of 30 and 3 s dominate the dynamic frequency spectrum. The results indicate that these waves propagate in the fast magnetosonic and Alfven/Ion Cyclotron modes, respectively. Both waves propagate in the upstream direction in the plasma rest frame but are convected downstream in the spacecraft frame. The measured wave properties in the plasma rest frame are in good agreement with those obtained from the theoretical kinetic dispersion relation taking into account the effects of different plasma beta. The dispersion results show a rather significant deviation from fluid model, especially when high beta plasma conditions occur. These experimentally derived foreshock ULF wave properties are in good agreement with previous results but when the effects of a high beta plasma are considered it is not as straight forward to choose the correct wave mode branch. (c) 2007 Elsevier Ltd. All rights reserved.
Scientific journal, English

Characteristics of terrestrial foreshock ULF waves: Cluster observations
Y. Hobara; S. N. Walker; M. Balikhin; O. A. Pokhotelov; M. Dunlop; H. Nilsson; H. Reme
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 112, A7, Jul. 2007, Peer-reviwed, [1] ULF waves in the terrestrial foreshock observed simultaneously by the four Cluster satellites were analyzed to identify the plasma wave modes and to study the effect of plasma beta on the intrinsic wave properties. The wave properties in the spacecraft and solar wind frames, such as the wave frequency, total wave number, phase speed, and wave polarization, are experimentally derived using the minimum variance analysis (MVA) for the case study and the phase differencing (MVA-free) technique for the statistical study. Both studies indicate that the waves with a 30 s period propagate in the upstream direction at a finite angle with respect to the background magnetic field in the plasma rest frame but are then convected downstream in the spacecraft frame. It is shown that these waves propagate in the fast magnetosonic mode. A similar analysis of the 3 s period waves shows them to be propagating in the upstream direction in the Alfven/ion cyclotron mode. The measured wave properties in the plasma rest frame are in good agreement with theoretical kinetic dispersion relation with a different plasma beta, which has rather significant deviation from fluid model especially for the high plasma beta. In conclusion it is found that the experimentally derived foreshock ULF wave properties are basically in good agreement with previous results but the effect of plasma beta is indispensable to choose the correct wave mode branch especially for the high plasma beta condition.
Scientific journal, English

Cluster observations of electrostatic solitary waves near the Earth’s bow shock
Y. Hobara; S. N. Walker; M. Balikhin; O. A. Pokhotelov; M. Andre; M. Dunlop; H. Reme
General Assembly of European Geophysical Union, -, 2007, Peer-reviwed
International conference proceedings, English

Mesoscale lightning in West African squall lines and its global detection with ELF measurements
Y. Hobara; E. Williams; R. Boldi; G. Satori; J. Bor; W. Lyons; T. Nelson; M. Hayakawa; N. Nathou; B. Russell
General Assembly of European Geophysical Union, -, 2007, Peer-reviwed
International conference proceedings, English

Cluster observations of scales in the quasi-perpendicular collisionless shocks
H. Alleyne; Y. Hobara; M. Balikhin; S. Walker; O. Pokhotelov; M. Dunlop; H. Reme
American Geophysical Union Fall Meeting, -, 2007, Peer-reviwed
International conference proceedings, English

ELF Q-bursts from African squall lines
Y. Hobara; E. Williams; V. Mushtak; R. Boldi; M. Hayakawa; K. Yamashita; W. Lyons; B. Russell; G. Satori; J. Bor; C. Price; E. Greenberg; R. Holzworth
American Geophysical Union Fall Meeting, -, 2007, Peer-reviwed
International conference proceedings, English

Electrostatic solitary waves in the vicinity of the terrestrial bow shock
Y. Hobara; S. Walker; M. Balikhin; M. Gedalin; V. Krasnoselskikh; M. Hayakawa; M. Andre; M. Dunlop; H. Reme; A. Fazakerley
American Geophysical Union Fall Meeting, -, 2007, Peer-reviwed
International conference proceedings, English

Lightning flashes conducive to the production and escape of gamma radiation to space
Earle Williams; R. Boldi; J. Bór; G. Sátori; C. Price; E. Greenberg; Y. Takahashi; K. Yamamoto; Y. Matsudo; Y. Hobara; M. Hayakawa; T. Chronis; E. Anagnostou; D. M. Smith; L. Lopez
Journal of Geophysical Research Atmospheres, Blackwell Publishing Ltd, 111, 16, 27 Aug. 2006, Peer-reviwed, Gamma radiation observed in space has been associated with lightning flashes in thunderstorms. These special flashes do not appear to be the large and energetic positive ground flashes that also produce sprites. Considerations of gamma ray attenuation in air indicate that such flashes may not produce gamma radiation at sufficient altitude to enable their escape to space. High-altitude intracloud lightning, most prevalent in the tropics where the tropopause is also high, may be a necessary source. Copyright 2006 by the American Geophysical Union.
Scientific journal, English

Lightning flashes conducive to the production and escape of gamma radiation to space
E. Williams; R. Boldi; J. Bor; G. Satori; C. Price; E. Greenberg; Y. Takahashi; K. Yamamoto; Y. Matsudo; Y. Hobara; M. Hayakawa; T. Chronis; E. Anagnostou; D. M. Smith; L. Lopez
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, AMER GEOPHYSICAL UNION, 111, D16, Aug. 2006, Peer-reviwed, [ 1] Gamma radiation observed in space has been associated with lightning flashes in thunderstorms. These special flashes do not appear to be the large and energetic positive ground flashes that also produce sprites. Considerations of gamma ray attenuation in air indicate that such flashes may not produce gamma radiation at sufficient altitude to enable their escape to space. High-altitude intracloud lightning, most prevalent in the tropics where the tropopause is also high, may be a necessary source.
Scientific journal, English

Sprite-attributed infrasonic chirps - their detection, occurrence and properties between 1994 and 2004
Ludwik Liszka; Yasuhide Hobara
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 68, 11, 1179-1188, Jul. 2006, Peer-reviwed, During the last 10 years, infrasonic chirps in the frequency range 0.5-8 Hz were occasionally observed by arrays belonging to the Swedish Infrasonic Network (SIN). These chirps have been attributed to certain types of thunderstorm activity associated with the high-altitude discharges, sprites [Liszka, L., 2004. On the possible infrasound generation by sprites, Journal of Low Frequency Noise, Vibration and Active Control 23, 85-93]. A method for automatic detection of chirps in the recorded data has been developed and applied to 10 years of data from two arrays belonging to the SIN: Jamton and Lycksele. The temporal and directional distribution of the phenomenon is described. Also, long-term variability and possible relation to the solar cycle is studied. (C) 2006 Elsevier Ltd. All rights reserved.
Scientific journal, English

The DEMETER Science Mission Centre
D Lagoutte; JY Brochot; D de Carvalho; F Elie; F Harivelo; Y Hobara; L Madrias; M Parrot; JL Pincon; JJ Berthelier; D Peschard; E Seran; M Gangloff; JA Sauvaud; JP Lebreton; S Stverak; P Travnicek; J Grygorczukf; J Slominski; R Wronowski; S Barbier; P Bernard; A Gaboriaud; JM Wallut
PLANETARY AND SPACE SCIENCE, PERGAMON-ELSEVIER SCIENCE LTD, 54, 5, 428-440, Apr. 2006, Peer-reviwed, The DEMETER Scientific Mission Centre (SMC) has been developed and is operated by the Laboratoire de Physique et Chimie de l'Environnement (LPCE). The SMC commands the instruments of the scientific payload, collects and distributes DEMETER data and associated products to the DEMETER international community.
The SMC has been designed to maximize scientific return and to reduce development and exploitation costs for the DEMETER project. This paper describes the SMC's data processing system, data server and methods of payload operation, and presents associated hardware and software architectures. (c) 2006 Elsevier Ltd. All rights reserved.
Scientific journal, English

Location and electrical properties of sprite-producing lightning from a single elf site
Yasuhide Hobara; M. Hayakawa; E. Williams; R. Boldi; E. Downes
SPRITES, ELVES AND INTENSE LIGHTNING DISCHARGES, SPRINGER, 225, 211-+, 2006, Peer-reviwed, Recently discovered TLEs (Transient Luminous Events) such as red sprites and elves provided a great opportunity to revisit the electromagnetic waves in the lower ELF (Extremely Low Frequency) region known as the Schumann resonances (SR). The resonance behavior is afforded by the low attenuation experienced by electromagnetic waves in this frequency range. Since TLEs are caused by energetic lightning with abundant energy in this range, these so-called ELF transients can be analyzed on a global basis from single measurement stations. In particular, the geographical location and the vertical charge moment of the lightning flash may be determined remotely. In this chapter, we aim at providing readers with an overview of electromagnetic waves from lightning in the SR frequency band. Then we introduce the technique to determine the location and demonstrate the global mapping of lightning for different thresholds of charge moment change based on the ELF transient observations in Rhode Island, USA. Meteorological interpretations of the global maps are also provided. Furthermore the sprite-producing winter lightning activity is characterized in Hokuriku by using the ELF field site in Moshiri, Japan. The generation condition for winter sprites and their coupling to the tropospheric lightning and to the ionosphere are also presented.
International conference proceedings, English

Characteristics of the sprite parent winter thundercloud with positive single flash in Hokuriku, Japan (a case study on 14th December 2001)
Tomoyuki Suzuki; Masashi Hayakawa; Yasuhide Hobara; Koichiro Michimoto; Takashi Hanada
IEEJ Transactions on Fundamentals and Materials, 126, 2, 78-83, 2006, Peer-reviwed, The sprite campaign was conducted by the sprite research group of University of Electro-Communications (UEC) during the winter of 2001/2002. On 14th December 2001, nine sprites were observed from Shimizu in Shizuoka and ELF transients were measured at Moshiri in Hokkaido. One of the sprites was also observed by the weather radar and the field mill network around the Komatsu Air Base. The sprite parent thunderclouds associated with the positive cloud-to-ground flash (+CG) were investigated with special reference to their electrical and meteorological characteristics. The results are summarized as follows
(1) The sprite parent thundercloud was very small (horizontal scale is at most 30 km) and the sprite was generated by a single flash when the thunderclouds were dissipating just after the maximum activity. (2) The sprite parent +CG occurred under the stratiform region of the thunderclouds. (3) Before the sprite causative +CG occurred, very large positive charge and negative one were found in and over the thundercloud by the analysis of sequential field mill observation.
Scientific journal, English

Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study
H. Nilsson; M. Waara; S. Arvelius; O. Marghitu; M. Bouhram; Y. Hobara; M. Yamauchi; R. Lundin; H. Reme; J. -A. Sauvaud; I. Dandouras; A. Balogh; L. M. Kistler; B. Klecker; C. W. Carlson; M. B. Bavassano-Cattaneo; A. Korth
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 24, 3, 1099-1112, 2006, Peer-reviwed, The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment. data for both hydrogen ions (HI) and oxygen ions (O+) from 3 years (2001-2003) of spring orbits (January to May) have been used. The altitudes covered were mainly in the range 5-12 RE geocentric distance. It was found that O+ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O+ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O+ parallel bulk velocities in excess of 60 km s(-1) were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O+ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H+ and O+ was found to typically be close to the same throughout the observation interval when the H+ bulk velocity was calculated for all pitch-angles. When the H+ bulk velocity was calculated for upward moving particles only the H+ parallel bulk velocity was typically higher than that of O+. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O+ ions dominates. The thermal velocity of O+ was always well below that of H+. Thus perpendicular energization that is more effective for O+ takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel acceleration. In particular centrifugal acceleration of the outflowing ions, which may provide the same parallel velocity increase to the two ion species and a two-stream interaction are discussed in the context of the measurements.
Scientific journal, English

Evidence on a link between the intensity of Schumann resonance and global surface temperature
M. Sekiguchi; M. Hayakawa; A. P. Nickolaenko; Y. Hobara
ANNALES GEOPHYSICAE, COPERNICUS PUBLICATIONS, 24, 7, 1809-1817, 2006, Peer-reviwed, A correlation is investigated between the intensity of the global electromagnetic oscillations (Schumann resonance) with the planetary surface temperature. The electromagnetic signal was monitored at Moshiri (Japan), and temperature data were taken from surface meteorological observations. The series covers the period from November 1998 to May 2002. The Schumann resonance intensity is found to vary coherently with the global ground temperature in the latitude interval from 45 degrees S to 45 degrees N: the relevant cross-correlation coefficient reaches the value of 0.9. It slightly increases when the high-latitude temperature is incorporated. Correspondence among the data decreases when we reduce the latitude interval, which indicates the important role of the middle-latitude lightning in the Schumann resonance oscillations. We apply the principal component (or singular spectral) analysis to the electromagnetic and temperature records to extract annual, semiannual, and interannual variations. The principal component analysis (PCA) clarifies the links between electromagnetic records and meteorological data.
Scientific journal, English

Intensity of Schumann resonance oscillations and the ground surface temperature
M. Hayakawa; M. Sekiguchi; Y. Hobara; A. P. Nickolaenko
J. Atmos. Electr., 26, 79-93, 2006, Peer-reviwed
Scientific journal, English

Mode identification of terrestrial foreshock ULF waves observaed by Cluster
Y. Hobara; S. N. Walker; M. Balikhin; M. Dunlop; O. A. Pokhotelov; H. Nilsson; H. Reme
Dynamical Process in Space Plasmas, -, 2006, Peer-reviwed
International conference proceedings, English

Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study
H. Nilsson; M. Waara; S. Arvelius; O. Marghitu; M. Bouhram; Y. Hobara; M. Yamauchi; R. Lundin; H. Reme; J. -A. Sauvaud; I. Dandouras; A. Balogh; L. M. Kistler; B. Klecker; C. W. Carlson; M. B. Bavassano-Cattaneo; A. Korth
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 24, 3, 1099-1112, 2006, Peer-reviwed, The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment. data for both hydrogen ions (HI) and oxygen ions (O+) from 3 years (2001-2003) of spring orbits (January to May) have been used. The altitudes covered were mainly in the range 5-12 RE geocentric distance. It was found that O+ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O+ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O+ parallel bulk velocities in excess of 60 km s(-1) were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O+ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H+ and O+ was found to typically be close to the same throughout the observation interval when the H+ bulk velocity was calculated for all pitch-angles. When the H+ bulk velocity was calculated for upward moving particles only the H+ parallel bulk velocity was typically higher than that of O+. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O+ ions dominates. The thermal velocity of O+ was always well below that of H+. Thus perpendicular energization that is more effective for O+ takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel acceleration. In particular centrifugal acceleration of the outflowing ions, which may provide the same parallel velocity increase to the two ion species and a two-stream interaction are discussed in the context of the measurements.
Scientific journal, English

Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study
H. Nilsson; M. Waara; S. Arvelius; O. Marghitu; M. Bouhram; Y. Hobara; M. Yamauchi; R. Lundin; H. Reme; J. -A. Sauvaud; I. Dandouras; A. Balogh; L. M. Kistler; B. Klecker; C. W. Carlson; M. B. Bavassano-Cattaneo; A. Korth
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 24, 3, 1099-1112, 2006, Peer-reviwed, The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment. data for both hydrogen ions (HI) and oxygen ions (O+) from 3 years (2001-2003) of spring orbits (January to May) have been used. The altitudes covered were mainly in the range 5-12 RE geocentric distance. It was found that O+ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O+ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O+ parallel bulk velocities in excess of 60 km s(-1) were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O+ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H+ and O+ was found to typically be close to the same throughout the observation interval when the H+ bulk velocity was calculated for all pitch-angles. When the H+ bulk velocity was calculated for upward moving particles only the H+ parallel bulk velocity was typically higher than that of O+. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O+ ions dominates. The thermal velocity of O+ was always well below that of H+. Thus perpendicular energization that is more effective for O+ takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel acceleration. In particular centrifugal acceleration of the outflowing ions, which may provide the same parallel velocity increase to the two ion species and a two-stream interaction are discussed in the context of the measurements.
Scientific journal, English

Ionospheric perturbations linked to a very powerful seismic event
Y Hobara; M Parrot
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 67, 7, 677-685, May 2005, Peer-reviwed, Ionospheric anomalies in association with the powerful Hachinohe earthquake (M = 8.3) are derived using foF2 (F2 layer 0-mode critical frequency) records from worldwide ionospheric stations. The results show that meaningful decreases in foF2 are identified only at several ionospheric stations near the epicenter, indicating that the anomalies extend to about 1500 km from the epicenter. These anomalies are observed a couple of days before and/or after the main shock and the duration of each anomaly is one-day. The anomalies occur predominantly during daytime. © 2005 Elsevier Ltd. All rights reserved.
Scientific journal, English

Cluster observations and theoretical identification of broadband waves in the auroral region
M Backrud-Ivgren; G Stenberg; M Andre; M Morooka; Y Hobara; S Joko; K Ronnmark; N Cornilleau-Wehrlin; A Fazakerley; H Reme
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 23, 12, 3739-3752, 2005, Peer-reviwed, Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves), while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV) plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.
Scientific journal, English

Statistics of high-altitude and high-latitude O+ ion outflows observed by Cluster/CIS
S Arvelius; M Yamauchi; H Nilsson; R Lundin; Y Hobara; H Reme; MB Bavassano-Cattaneo; G Paschmann; A Korth; LM Kistler; GK Parks
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 23, 5, 1909-1916, 2005, Peer-reviwed, The persistent outflows of O+ ions observed by the Cluster CIS/CODIF instrument were studied statistically in the high-altitude (from 3 up to I I RE) and high-latitude (from 70 to similar to 90 deg invariant latitude, ILAT) polar region. The principal results are: (1) Outflowing O+ ions with more than 1 keV are observed above 10 R-E geocentric distance and above 85 deg ILAT location; (2) at 6-8 R-E geocentric distance, the latitudinal distribution of O+ ion outflow is consistent with velocity filter dispersion from a source equatorward and below the spacecraft (e.g. the cusp/cleft); (3) however, at 8-12 R-E geocentric distance the distribution of O+ outflows cannot be explained by velocity filter only. The results suggest that additional energization or acceleration processes for outflowing O+ ions occur at high altitudes and high latitudes in the dayside polar region.
Scientific journal, English

New ELF observation system at Moshiri, Japan, and assessments of acquired data
Y. Ando; P. Maltsev; A. Sukhynyuk; T. Goto; T. Yamauchi; Y. Hobara; M. Sekiguchi; Y. Ikegami; M. Sera; V. Korepanov; M. Hayakawa
J. Atmos. Electr., 25, 1, 29-39, 2005, Peer-reviwed
Scientific journal, English

Low-latitude ionospheric turbulence observed by Aureol-3 satellite
Y Hobara; F Lefeuvre; M Parrot; OA Molchanov
ANNALES GEOPHYSICAE, EUROPEAN GEOSCIENCES UNION, 23, 4, 1259-1270, 2005, Peer-reviwed, Using PSD (Power Spectral Density) data on electron density and electric field variations observed on board Aureol-3 satellite at low-to-mid-latitude ionosphere we analyze a scale distribution of the ionospheric turbulence in a form k(--alpha), where k is the wave number and a is the spectral index. At first, high-resolution data in the near-equator region for several orbits have been processed. In this case the frequency range is from 6 Hz to 100 Hz (corresponding spatial scales from 80 m to 1.3 km), each power spectrum obeys a single power law fairly well, and the mean spectral indices are rather stable with alpha(N)=2.2 +/- 0.3 and alpha(E)=1.8 +/- 0.2, for the density and electric field, respectively. Then we produce a statistical study of 96 electric field bursts in the frequency range 10-100 Hz from low-time resolution data (filter bank envelope). These bursts concentrate on the side of the Equatorial Anomaly crest (geomagnetic latitude 30-10). Spectral indices of the bursts vary in the interval alpha(E)=2.0-2.5 but are fairly stable in seasons and local times. The electric field power of the burst has rather a large variability but has a relative increase in mean values for the summer and winter, as well as the daytime. The effect of major seismic activities toward the ionospheric turbulence is not conclusive either for the refractive index or for the electric field power. However, the mean value for the electric field power of bursts during seismic periods is larger than that for non seismic periods, and the statistical difference of the mean values is rather significant.
Scientific journal, English

Multi-spacecraft determination of wave characteristics near the proton gyrofrequency in high-altitude cusp
D Sundkvist; A Vaivads; M Andre; JE Wahlund; Y Hobara; S Joko; VV Krasnoselskikh; YV Bogdanova; SC Buchert; N Cornilleau-Wehrlin; A Fazakerley; JO Hall; H Reme; G Stenberg
ANNALES GEOPHYSICAE, COPERNICUS GESELLSCHAFT MBH, 23, 3, 983-995, 2005, Peer-reviwed, We present a detailed study of waves with frequencies near the proton gyrofrequency in the high-altitude cusp for northward IMF as observed by the Cluster spacecraft. Waves in this regime can be important for energization of ions and electrons and for energy transfer between different plasma populations. These waves are present in the entire cusp with the highest amplitudes being associated with localized regions of downward precipitating ions, most probably originating from the reconnection site at the magnetopause. The Poynting flux carried by these waves is downward/upward at frequencies below/above the proton gyrofrequency, which is consistent with the waves being generated near the local proton gyrofrequency in an extended region along the flux tube. We suggest that the waves can be generated by the precipitating ions that show shell-like distributions. There is no clear polarization of the perpendicular wave components with respect to the background magnetic field, while the waves are polarized in a parallel-perpendicular plane. The coherence length is of the order of one ion-gyroradius in the direction perpendicular to the ambient magnetic field and a few times larger or more in the parallel direction. The perpendicular phase velocity was found to be of the order of 100 km/s, an order of magnitude lower than the local Alfven speed. The perpendicular wavelength is of the order of a few proton gyroradius or less. Based on our multi-spacecraft observations we conclude that the waves cannot be ion-whistlers, while we suggest that the waves can belong to the kinetic Alfven branch below the proton gyrofrequency f(cp) and be described as non-potential ion-cyclotron waves (electromagnetic ion-Bernstein waves) above. Linear wave growth calculations using kinetic code show considerable wave growth of non-potential ion cyclotron waves at wavelengths agreeing with observations. Inhomogeneities in the plasma on the order of the ion-gyroradius suggests that inhomogeneous (drift) or nonlinear effects or both of these should be taken into account.
Scientific journal, English

Cluster observations of high altitude oxygen outflow burst and associated wave activities
Y. Hobara; H. Nilsson; S. Arvelius; R. Lundin; D. Sundkvist; M. Andre; N. Cornilleau-Wehrlin
General assembly of European Geophysical Union, -, 2005, Peer-reviwed
International conference proceedings, English

Sprite-attributed infrasonic chirps – their detection, occurrence and properties between 1994 and 2004
L. Liszka; Y. Hobara
IAGA, -, 2005, Peer-reviwed
International conference proceedings, English

Cluster observations of high altitude oxiygen outflow burst and associated wave activities
Y. Hobara; H. Nilsson; S. Arvelius; R. Lundin; D. Sundkvist; M. Andre; N. Cornilleau-Wehrlin
IAGA, -, 2005, Peer-reviwed
International conference proceedings, English

Cluster observations of high altitude oxygen outflow burst and associated wave activities
Y. Hobara; H. Nilsson; S. Arvelius; R. Lundin; D. Sundkvist; M. Andre; N. Cornilleau-Wehrlin; A. Balogh; S. C. Buchert; H. Reme; J.-A. Sauvaud
EISCAT Workshop, -, 2005, Peer-reviwed
International conference proceedings, English

Observation of sprites over the Sea of Japan and conditions for lightning-induced sprites in winter
M Hayakawa; T Nakamura; Y Hobara; E Williams
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 109, A1, Jan. 2004, Peer-reviwed, [1] We have succeeded in observing sprites for winter lightning in the Hokuriku area ( Japan Sea side) of Japan in the winter of 2001/2002. The optical results on 3 days are compared with the corresponding characteristics of parent ( causative) lightning with particular attention to the significant differences between Hokuriku winter lightning and the more widely studied continental lightning. Despite significant differences with Hokuriku winter lightning, we have found nearly the same sprite properties as already observed in the U. S. continent with a significant difference ( simpler shape for Hokuriku winter sprite). Then, we have also discussed the criteria for sprite occurrence. Specifically, two similar criteria are found: ( 1) cloud-to-ground discharges of positive polarity and ( 2) the presence of a certain threshold in vertical charge moment ( 200 - 300 C km) ( roughly consistent with that for the U. S. continent). Mesoscale convective systems are not necessary to store the charge necessary for sprites, but the parent Hokuriku winter clouds are substantially smaller than the minimum scale for sprite occurrence in the continental lightning; however, it is larger in area than ordinary summer thunderclouds. However, there may exit another condition such as clustering or self-organizing effect of thunderclouds for sprite production.
Scientific journal, English

Links of Schumann resonance intensity with average global land temperature
M. Sekiguchi; M. Hayakawa; Y. Hobara; A. Nickolaenko; E. Williams
Radio Physics and Electronics, 9, 2, 383-391, 2004, Peer-reviwed
Scientific journal

Characteristics of ULF magnetic anomaly before earthquakes
Y Hobara; HC Koons; JL Roeder; K Yumoto; A Hayakawa
PHYSICS AND CHEMISTRY OF THE EARTH, PERGAMON-ELSEVIER SCIENCE LTD, 29, 4-9, 437-444, 2004, Peer-reviwed, We analyze the ULF magnetic field emissions observed at three different field sites. Large seismic events occurred near each station. Temporal dependence of the polarization ratio (ratio of horizontal to vertical magnetic field components) has been calculated in the frequency range between 1.17 mHz and 0.5 Hz with longer than 2-year data for each event. Two of three seismic events were associated with anomalous change in the polarization ratio. Remarkable similarities were found in the ratio between these two different seismic events: (1) The ratio has a significant increase about 1 month before the earthquake (about two times larger than usual level), (2) the increase is seen in the nighttime period (22-02 LT). The frequency range of increase in the ratio depends on the earthquake (0.01-0.022 Hz for the Izu Island earthquake swarms and 0.05-0.1 Hz for the Guam earthquake). Calculated ratio based on the simple theoretical model has a good agreement with observed values for these two earthquakes. (C) 2004 Elsevier Ltd. All rights reserved.
Scientific journal, English

Summary report of NASDA's earthquake remote sensing frontier project
M Hayakawa; OA Molchanov
PHYSICS AND CHEMISTRY OF THE EARTH, PERGAMON-ELSEVIER SCIENCE LTD, 29, 4-9, 617-625, 2004, Peer-reviwed, After the disastrous Kobe earthquake, the former Science and Technology Agency (STA) of Japanese Government proposed the Integrated Earthquake Frontier Project. Within the framework of this project, two institutions (RIKEN and NASDA (National Space Development Agency of Japan)) were asked to carry out over five years a feasibility study of the use of electromagnetic phenomena in short-term earthquake prediction. Since 1996 the RIKEN group has been engaged in the study of earth current and related phenomena. Meanwhile, under the NASDA project named "Earthquake Remote Sensing Frontier Project", we performed an overall study of seismo-electromagnetic phenomena occurring not only in the lithosphere, but also in the atmosphere and ionosphere. Our five-year study has yielded that the seismic effect expresses itself not only in the lithosphere (such as by ULF electromagnetic emissions, acoustic emissions etc.), but also in the atmosphere and ionosphere (by means of pre-existing transmitter signals). Most importantly, we find convincing evidence for seismo-ionospheric perturbations on the basis of subionospheric VLF/LF signals. We have established a new challenging science field, "Litho sphere-atmosphere-ionosphere coupling" or "Electromagnetics in the coupled lithosphere-atmosphere-ionosphere system". The study of this coupling would contribute to the scientific short-term earthquake prediction. (C) 2004 Elsevier Ltd. All rights reserved.
Scientific journal, English

Localized waves near proton gyrofrequency in high-altitude cusp: Novel results from Cluster multi-spacecraft observations
D. Sundkvist; A. Vaivads; J. E. Wahlund; M. Andre; J. O. Hall; Y. V. Bogdanova; S. Buchert; N. Cornilleau-Wehrlin; Y. Hobara; G. Stenberg
General Assembly of European Geophysical Union, -, 2004, Peer-reviwed
International conference proceedings, English

Comparative study of ULF emissions associated with large earthquakes
Y. Hobara; H. C. Koons; J. L. Roeder; K. Yumoto; M. Hayakawa
General Assembly of European Geophysical Union, -, 2004, Peer-reviwed
International conference proceedings, English

High altitude oxygen outflow observed by cluster satellites: Energization and subsequent wave activities
Y. Hobara; H. Nilsson; S. Joko; R. Lundin; D. Sundkvist; M. Andre; N. Cornilleau-Wehrlin
General Assembly of European Geophysical Union, -, 2004, Peer-reviwed
International conference proceedings, English

Phase-bunching effects in triggered VLF emissions: Antenna effect
VY Trakhtengerts; AG Demekhov; Y Hobara; M Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 108, A4, Apr. 2003, Peer-reviwed, [1] We consider the effect of initial phase bunching of energetic electrons on the generation of triggered ELF/VLF emissions in the magnetosphere. The electrons interacted with the primary whistler wave packet form a phase-bunched beam in the velocity space, which serves as a traveling-wave antenna emitting secondary waves. We calculate this antenna field and study its spectral and amplitude characteristics. It is shown that under the typical magnetospheric conditions, the secondary wave field is by about an order of magnitude smaller than the primary wave field. Therefore this antenna field is significant as the seed wave which is further amplified by the same beam via the cyclotron resonant mechanism. The frequency band of the antenna effect is of the order of 100 Hz near the primary-wave frequency. This is consistent with the observed frequency shift of triggered emissions.
Scientific journal, English

Phase-bunching effects in triggered VLF emissions: Antenna effect
V. Y. Trakhtengerts; A. G. Demekhov; Y. Hobara; M. Hayakawa
Journal of Geophysical Research: Space Physics, Blackwell Publishing Ltd, 108, 4, 2003, Peer-reviwed, We consider the effect of initial phase bunching of energetic electrons on the generation of triggered ELF/VLF emissions in the magnetosphere. The electrons interacted with the primary whistler wave packet form a phase-bunched beam in the velocity space, which serves as a traveling-wave antenna emitting secondary waves. We calculate this antenna field and study its spectral and amplitude characteristics. It is shown that under the typical magnetospheric conditions, the secondary wave field is by about an order of magnitude smaller than the primary wave field. Therefore this antenna field is significant as the seed wave which is further amplified by the same beam via the cyclotron resonant mechanism. The frequency band of the antenna effect is of the order of 100 Hz near the primary-wave frequency. This is consistent with the observed frequency shift of triggered lemissions. Copyright 2003 by the American Geophysical Union.
Scientific journal, English

Observation of sprites over the Sea of Japan and conditions for lightning-induced sprites in winter
M Hayakawa; T Nakamura; Y Hobara; E Williams
ASIA-PACIFIC CONFERENCE ON ENVIRONMENTAL ELECTROMAGNETICS, CEEM'2003, PROCEEDINGS, PUBLISHING HOUSE BEIJING UNIV POSTS & TELECOMMUNICATIONS, 533-535, 2003, Peer-reviwed, We have succeeded in observing sprites for winter lightning in the Hokuriku area (Japan Sea side) of Japan in the winter of 2001/2002. The optical results on three days are compared with the corresponding characteristics of parent (causative) lightning with particular attention to the significant differences between Hokuriku winter lightning and the more widely studied continental lightning. Despite significant differences with Hokuriku winter lightning. We have found nearly the same sprite properties as already observed in the U.S. continent with a significant difference (simpler shape for Hokuriku winter sprite). Then, we have also discussed the criteria for sprite occurrence. Specifically, two similar criteria are found: (1) cloud-to-ground discharges of positive polarity and (2) the presence of a certain threshold in vertical charge moment(2000-300C (.) km) (roughly consistent with that for the U.S. continent). Mesoscale convective systems are not necessary to store the charge necessary for sprites, but the parent Hokuriku winter clouds are substantially smaller than the minimum scale for sprite occurrence in the continental lightning, but it is larger in area than ordinary summer thunderclouds. However there may exit another condition such as clustering or self-organizing effect of thunderclouds for sprite production.
International conference proceedings, English

Lightning discharges in association with mesospheric tles and their effect to the lower ionosphere
Y. Hobara; M. Hayakawa; K. Ohta; H. Fukunishi
Advances in Polar Upper Atmospheric Research, National Institute of Polar Research, 17, 30-47, 2003, Peer-reviwed, A quantitative and statistical analysis was performed using data from coordinated measurements consisting of ELF waves, VLF subionospheric disturbances and lightning discharges associated with transient luminous events(TLEs). These TLEs(sprites and elves) were observed during winter lightning storms over the Sea of Japan in the winter of 1998/99. A clear, straightforward relationship was found between the charge moment of the parent discharge, calculated from ELF(f<15Hz) transients, and the ionospheric disturbances, with a correlation coefficient of 0.97 independent of the type of TLEs; this suggests significant atmosphere-mesosphere-ionosphere coupling and implies that a large quasi-electrostatic(QE) field change occurring above lightning discharges with TLEs plays a significant role in modifying the electrical properties of the lower ionosphere. Sprites tend to be associated with large ionospheric disturbancs(-13〜+ 4.6dB, compared with the unperturbed waves) and a large charge moment(260-875Ckm), whereas a relatively large lightning peak current(+223〜+ 470kA,)(or a slow-tail amplitude) leading to a strong electromagnetic pulse(EMP) but with a rather small ionospheric disturbances seems to be necessary to initiate elves.
Scientific journal, English

Variability of sporadic E-layer semi transparency (f(o)E(s) - f(b)E(s)) with magnitude and distance from earthquake epicenters to vertical sounding stations
E. V. Liperovskaya; O. A. Pokhotelov; Y. Hobara; M. Parrot
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, COPERNICUS GESELLSCHAFT MBH, 3, 3-4, 279-284, 2003, Peer-reviwed, Variations of the E-s- layer semi transparency coefficient were analyzed for more than 100 earthquakes with magnitudes M > 4 and depths h < 100 km. Data of mid latitude vertical sounding stations (Kokubunji, Akita, and Yamagawa) have been used for several decades before and after earthquake occurrences. The semi-transparency coefficient of E-s-layer X = ( f(o)E(s) - f(b)E(s))/fbEs can characterize, for thin layers, the presence of small scale plasma turbulence. It is shown that the turbulence level decreases by similar to 10% during three days before earthquakes probably due to the heating of the atmosphere. On the contrary, the turbulence level increases by the same value from one to three days after the shocks. For earthquakes with magnitudes M > 5 the effect exists at distances up to 300 km from the epicenters. The effect could also exist for weak ( M similar to 4) and shallow (depth < 50 km) earthquakes at a distance smaller than 200 km from the epicenters.
Scientific journal, English

ELF transients and ionospheric disturbances in association with sprites and elves
Y. Hobara; M. Hayakawa; K. Ohta; H. Fukunishi; E. R. Williams
The 12th International Conference on Atmospheric Electricity, 307-316, 2003, Peer-reviwed
International conference proceedings, English

Ionospheric turbulence associated with seismic activity from Aureol-3 satellite data
Y. Hobara; M. Parrot; F. Lefeuvre; O.A. Molchanov
EGS-AGU-EUG Joint Assembly, -, 2003, Peer-reviwed
International conference proceedings, English

Optical phenomena in association with lightning and various related phenomena
M. Hayakawa; T. Otsuyama; Y. Hobara; T. Nakamura
Applied Optics, 2, 14-21, 2002, Peer-reviwed
Scientific journal, Japanese

ULF/ELF observation in Seikoshi, Japan, and the precursory signal for recent large seismic events
Y. Hobara; H. C. Koons; J. L. Roeder; M. Hayakawa
URSI 2002 General Assembly, -, 2002, Peer-reviwed
International conference proceedings, English

Global mapping of lightning activity by using a single station based on ELF transients observed in Japan
Y. Hobara; M. Hayakawa; E. R. Williams
URSI 2002 General Assembly, -, 2002, Peer-reviwed
International conference proceedings, English

Ionospheric perturbation in association with seismic activity, a statistical study
Y. Hobara; M. Parrot
URSI 2002 General Assembly, -, 2002, Peer-reviwed
International conference proceedings, English

Interrelation between ELF transients and ionospheric disturbances in association with sprites and elves
Y. Hobara; M. Hayakawa; K. Ohta; H. Fukunishi; E. R. Williams
URSI 2002 General Assembly, -, 2002, Peer-reviwed
International conference proceedings, English

A role of the second-order cyclotron resonance effect in a self-consistent approach to triggered VLF emissions
VY Trakhtengerts; Y Hobara; AG Demekhov; M Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 106, A3, 3897-3904, Mar. 2001, Peer-reviwed, A role of the second-order cyclotron resonance effect in the self-consistent approach to the problem of triggered ELF/VLF emissions is estimated. The self-consistency includes the calculation of energetic electron beams produced by a quasimonochromatic whistler wave packet and the analysis of secondary whistler wave generation by this beam with the magnetic field inhomogeneity taken into account. The theory allows one to estimate the maximum amplification of the secondary waves, as well as the dynamic frequency spectrum of a triggered emission. A simple computer program has been realized to find dynamic spectrograms of triggered VLF signals in particular cases with realistic dependences of electron beam velocity and geomagnetic field on the spatial coordinate and time. The main and general conclusions are summarized as follows: (1) The second-order cyclotron resonance effects give an important contribution to the formation of the dynamic frequency spectrum of triggered ELF/VLF emissions. (2) The short pump whistler wave packets (with pulse durations 0.5-0.7 s in our case) generate fallers, while the long packets (pulse durations 0.9-1.3 s) generate predominantly rising tones. (3) There are critical maximal and minimal values for the pump wave pulse duration, when triggered emissions are not generated in the absence of an external electron beam.
Scientific journal, English

Interrelation between ELF transients and ionospheric disturbances in association with sprites and elves
Y Hobara; N Iwasaki; T Hayashida; M Hayakawa; K Ohta; H Fukunishi
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 28, 5, 935-938, Mar. 2001, Peer-reviwed, Red sprites and elves were observed in Japan during the winter of 1998/99 in Hokuriku region by the group of Tohoku Univ. [Fukunishi et al., EOS, 80(46), F217, 1999]. We analyze quantitatively the results from coordinated measurement consisting of ELF transients, VLF subionopheric disturbances and lightning discharges associated with the optical events. We find the clear straightforward relationship between charge transfer of the parent discharge calculated from ELF (f<15 Hz) and the ionospheric disturbances regardless of the types of optical events indicating significant atmosphere-mesosphere-ionosphere coupling. Sprites tend to associate with a large ionospheric disturbance (-13<similar to>+4.6 dB) with a large charge transfer (52 similar to 175 C), whereas a large lightning peak current (+223 similar to +470 kA) (or slow-tail amplitude) leading to the strong EMP is necessary to initiate elves, but with rather small ionospheric disturbances.
Scientific journal, English

Cyclotron amplification of whistler waves by nonstationary electron beams in an inhomogeneous magnetic field
AG Demekhov; VY Trakhtengerts; Y Hobara; M Hayakawa
PHYSICS OF PLASMAS, AMER INST PHYSICS, 7, 12, 5153-5158, Dec. 2000, Peer-reviwed, The linear amplification of whistler waves with varying frequency by beams of energetic electrons in the inhomogeneous magnetic field is studied. Rigorous treatment developed by Trakhtengerts et al. [Phys Plasmas 6, 692 (1999)] for the distribution function with a steplike deformation over parallel velocities is applied here for the delta -like distribution which is appropriate for triggered emissions. The formalism developed enables one to determine the one-hop amplification of a wavelet with variable frequency and the "optimal" spatio-temporal variation of the frequency corresponding to the maximum amplification; we show this variation to coincide with the so-called second-order cyclotron resonance condition, similarly to the case of the steplike distribution. The results allow one to compare the dependence of the maximum amplification on characteristic parameters of a plasma in the magnetic trap for smooth, steplike, and beamlike distributions. (C) 2000 American Institute of Physics. [S1070-664X(00)00712-6].
Scientific journal, English

Formation of electron beams by the interaction of a whistler wave packet with radiation belt electrons
Y Hobara; VY Trakhtengerts; AG Demekhov; M Hayakawa
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 62, 7, 541-552, May 2000, Peer-reviwed, The purpose of this paper is to discuss the properties of electron beams formed by cyclotron interactions between radiation belt electrons and a quasi-monochromatic whistler wave packet from a ground-based VLF transmitter. The beams are formed due to trapping of the electrons at the forward edge of the wave packet, their acceleration inside the wave packet, the escape of the accelerated electrons from the moving backward edge of the wave packet, and their following free motion in an inhomogeneous magnetic field. A combination of these processes provides the main features of the spatial-temporal evolution of the beams which are investigated both analytically and numerically. It is shown that one or two beams can appear at one point at the same time, and that the density of the beams increases during their expansion. Motion of the pumping wave packet in the inhomogeneous magnetic field provides the variations of the initial velocity and position of the beam injection which change the spatial and temporal gradients of the parallel velocity of the beam, in contrast with the case of the pure adiabatic motion of an individual electron. Such a behaviour can be significant for the generation of secondary emissions. Numerical calculations demonstrate a wide variety of the spatio-temporal patterns of the beam parallel velocity depending on the plasma and wave packet parameters. It is shown that the most significant parameters which determine the beam characteristics are the wave packet length about the equator, its group velocity, and the initial energy and pitch angle of the electrons. (C) 2000 Elsevier Science Ltd. All rights reserved.
Scientific journal, English

New ELF observation site in Moshiri, Hokkaido Japan, and the results of preliminary data analysis
Y. Hobara; N. Iwasaki; T. Hayashida; N. Tsuchiya; E. R. Williams; M. Sera; Y. Ikegami; M. Hayakawa
J. Atmos. Electr., 20, 99-109, 2000, Peer-reviwed
Scientific journal, English

Wide-band ULF/ELF magnetic field measurement in Seikoshi, Izu Japan, and some results from preliminary data analysis in relation with seismic activity
Y. Hobara; H. Yamaguchi; T. Watanabe; Y. Akinaga; H. C. Koons; J. L. Roeder; M. Hayakawa
J. Atmos. Electr., 20, 111-121, 2000, Peer-reviwed
Scientific journal, English

Long-term periodical variations in global lightning activity deduced from the Schumann resonance monitoring
AP Nickolaenko; R Hayakawa; Y Hobara
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, AMER GEOPHYSICAL UNION, 104, D22, 27585-27591, Nov. 1999, Peer-reviwed, We deduce temporal variations of the level of global lightning activity from the long-term Schumann resonance (SR) monitoring performed at the Tottori observatory (35.5 degrees N, 134.33 degrees E). The continuous analog records of the horizontal magnetic field cover the period from August 1967 to November 1970. The data show that temporal changes of the SR amplitudes vary considerably from day to day. Meanwhile, the regular diurnal and longer-scale variations appear after averaging. We found annual, and semiannual components in variations of global thunderstorm activity between 1967 and 1970. Comparison with the long-term SR records made recently in Europe allows us to demonstrate the similarity and stability of the global thunderstorm variations on a seasonal scale. Simultaneously, it revealed a contribution from winter thunderstorms in the Japan Sea to the Tottori SR records.
Scientific journal, English

Beam-plasma instability in inhomogeneous magnetic field and second order cyclotron resonance effects
VY Trakhtengerts; Y Hobara; AG Demekhov; M Hayakawa
PHYSICS OF PLASMAS, AMER INST PHYSICS, 6, 3, 692-698, Mar. 1999, Peer-reviwed, A new analytical approach to cyclotron instability of electron beams with sharp gradients in velocity space (step-like distribution function) is developed taking into account magnetic field inhomogeneity and nonstationary behavior of the electron beam velocity. Under these conditions, the conventional hydrodynamic instability of such beams is drastically modified and second order resonance effects become important. It is shown that the optimal conditions for the instability occur for nonstationary quasimonochromatic wavelets whose frequency changes in time. The theory developed permits one to estimate the wave amplification and spatio-temporal characteristics of these wavelets. (C) 1999 American Institute of Physics. [S1070-664X(99)02003-0].
Scientific journal, English

Whistler cyclotron instability and second order cyclotron resonance effects in the magnetosphere
VY Trakhtengerts; Y Hobara; AG Demekhov; M Hayakawa
MICROSCOPIC PROCESSES IN SPACE PLASMAS AND THEIR ROLE IN MACROSCALE PHENOMENA, PERGAMON PRESS LTD, 24, 1, 35-42, 1999, Peer-reviwed, A new analytical approach to cyclotron instability of electron beams with sharp gradients in velocity space (step-like or delta distribution function) is developed taking into account magnetic field inhomogeneity and non-stationary behavior of the electron beam velocity. Under these conditions, the conventional hydrodynamic instability of such beams is drastically modified and second order resonance effects become important. It is shown that the optimal conditions for the instability occur for a non-stationary quasi-monochromatic wavelets whose frequency changes in time. The theory developed permits to estimate the wave amplification and spatiotemporal characteristics of these wavelets. The results obtained are important for interpretation of VLF/ELF triggered and chorus emissions. (C) 1999 COSPAR. Published by Elsevier Science Ltd.
Scientific journal, English

Cyclotron amplification of whistler waves
Y Hobara; VY Trakhtengerts; AG Demekhov; M Hayakawa
MICROSCOPIC PROCESSES IN SPACE PLASMAS AND THEIR ROLE IN MACROSCALE PHENOMENA, PERGAMON PRESS LTD, 24, 1, 95-98, 1999, Peer-reviwed, Cyclotron wave-particle interactions in the case of well-organized distributions of energetic electrons in ag inhomogeneous magnetic field are studied. Step and delta function distributions of field-aligned velocity are considered. The one-hop amplification of whistler waves is calculated analytically and by numerical computation. In rigorous approach, taking into account the third-order term in the spatial dependence of the electron phase with respect to the wave, some new features of the one-hop amplification rate Gamma as function of frequency and electron beam parameters are obtained. Gamma exhibits a quasi-periodic structure as function of frequency or characteristic electron parallel velocity. For the step-like distribution it remains positive. For the delta-function it changes sign. The dependence of Gamma on the total energy, characteristic parallel velocity, position of the injection point inn relation to the equator, and dispersion in parallel velocity of energetic electrons such as is discussed. (C) 1999 COSPAR. Published by Elsevier Science Ltd.
Scientific journal, English

Formation of electron beams under the interaction of a whistler wave packet with the radiation belt electrons
Y Hobara; VY Trakhtengerts; AG Demekhov; M Hayakawa
ACTIVE EXPERIMENTS IN SPACE PLASMAS, PERGAMON PRESS LTD, 24, 8, 1007-1010, 1999, Peer-reviwed, The purpose of this paper is to discuss the properties of electron beams formed by cyclotron interaction between radiation belt electrons and a quasi-monochromatic whistler wave packet from a ground-based VLF transmitter. Those electron beams are thought to be the source of triggered ELF/VLF emissions as secondary whistler waves. The beams are formed due to trapping of electrons at the forward front of the wave packet, their acceleration inside the packet, escape of the accelerated electrons from the moving backward front of the packet, and their following free motion in an inhomogeneous magnetic field. Combination of these processes provides the main features of the spatial-temporal evolution of the beams which are investigated analytically and numerically. Movement of the pumping wave packet in the inhomogeneous magnetic field provides the variations of the initial velocity and position of the beam injection which change the spatial and temporal gradients of the parallel velocity of the beam opposite direction to a pure adiabatic motion. Such a behavior can be significant for the generation of secondary emissions. (C) 1999 COSPAR. Published by Elsevier Science Ltd.
Scientific journal, English

Self-consistent theory of triggered VLF emissions: An analytical approach
VY Trakhtengerts; Y Hobara; AG Demekhov; M Hayakawa
ACTIVE EXPERIMENTS IN SPACE PLASMAS, PERGAMON PRESS LTD, 24, 8, 1011-1014, 1999, Peer-reviwed, The sell-consistent analytical approach to the problem of triggered ELF/VLF emissions is developed. The self-consistency includes calculation of energetic electron beams produced by a quasimonochromatic whistler wave packet from a around based VLF transmitter and analysis of secondary whistler wave generation by this beam, taking into account the second order cyclotron resonance effects. The theory permits estimation of the maximum amplification of the secondary waves as well as dynamical frequency spectrum of triggered emission. A simple computer program has been developed to find the dynamic spectrogram of triggered VLF signals with spatial and temporal dependences of electron beam velocity and geomagnetic field. (C) 1999 COSPAR. Published by Elsevier Science Ltd.
Scientific journal, English

Cyclotron amplification of whistler waves by electron beams in an inhomogeneous magnetic field
Y Hobara; VY Trakhtengerts; AG Demekhov; M Hayakawa
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 103, A9, 20449-20458, Sep. 1998, Peer-reviwed, Cyclotron wave-particle interactions in the case of well-organized distributions of energetic electrons under an inhomogeneous magnetic field are studied. Step-like and delta function distributions over the field-aligned velocity are considered. The one-hop amplification of whistler waves is calculated by simple analytical solution and numerical computation based on strict approach. The strict consideration, taking into account third-order expansion of the spatial dependence of the electron phase with respect to the wave, reveals some new important features of the one-hop amplification Gamma as a function of frequency and electron beam parameters. The main result is that Gamma exhibits a quasi-periodic structure as a function of wave frequency or characteristic electron parallel velocity, remaining always positive in the case of the step-like distribution but being sign alternative for delta-function. Dependence of Gamma on the parameters of energetic electrons such as their total energy: characteristic parallel velocity, position of the injection point in relation to the equator, and dispersion in parallel velocity is discussed.
Scientific journal, English

Schumann resonance and global lightning activity
AP Nickolaenko; M Hayakawa; Y Hobara
1998 INTERNATIONAL CONFERENCE ON MATHEMATICAL METHODS IN ELECTROMAGNETIC THEORY, VOLS 1 AND 2, IEEE, 296-297, 1998, Peer-reviwed, Temporal variations of the global lightning activity, are deduced from the long-term Schumann resonance (SA) continuous records. The intensities of the horizontal magnetic field component of the first, second, and third SR modes were monitored at the Tottori observatory (35.5 degrees N and 134.33 degrees E). Variations of the effective source-observer distance were estimated from the data using the ratios between intensities of individual SR modes. This allowed us to compensate for the source motion in respect to the observatory and extract from the records the average diurnal variations of the global lightning activity itself: The procedure: had been done for every month within the observation period. The results show that estimates for the effective distances between the field-site and the global centers of the lightning activity remain very stable. Simultaneously, the temporal changes of the fields monitored and of the relevant global lightning activity derived front the records demonstrate substantial variability.
International conference proceedings, English

On estimating the amplitude of Jovian whistlers observed by Voyager 1 and implications concerning lightning
Y Hobara; S Kanemaru; M Hayakawa; DA Gurnett
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 102, A4, 7115-7125, Apr. 1997, Peer-reviwed, In this paper we extensively reexamine the amplitude of many whistlers detected by the Voyager 1 and try to deduce information about the causative lightning discharges with the use of our ray-tracing computations taking into account the amplitude. As a result; we have derived the frequency spectra and mean radiation power of the causative lightning discharges and have also applied statistical method to the analysis. We can summarize our findings in the following. The average power flux spectral density of the whistlers falls in a range from 10(-12.7)V(2)m(-2)Hz(-1) to 10(-11.0)V(2)m(-2)Hz(-1). We calculated the total decrease of the whistler amplitude from the bottom of the ionosphere toward the spacecraft, as a range from about 30 to 40 dB. One of the strongest estimated lightning events exhibits a frequency dependence comparable to the terrestrial one; but its peak frequency seems to be similar to the upward current strokes on the Earth. Moreover, the rather smooth profile obtained implies a small possibility of the presence of stratified layers in the Jovian ionosphere. Other events possibly have features similar to those of the terrestrial return strokes. We calculated the mean radiation power per flash of the lightning in the Jovian atmosphere for a 1-kHz bandwidth over 60 ms, as a range from the order of 10(2) to 10(5) W. The probability distribution of the radiation power in Jupiter is found to follow a lognormal distribution, just as in the terrestrial case.
Scientific journal, English

Ducted propagation of lightning - generated whistlers in the Jovian magnetosphere
Y. Hobara; M. Hayakawa
J. Atmos. Electr, 17, 17, 33-45, 1997, Peer-reviwed
Scientific journal, English

Temporal variations of the global lightning activity deduced from the Schumann resonance data
AP Nickolaenko; M Hayakawa; Y Hobara
JOURNAL OF ATMOSPHERIC AND TERRESTRIAL PHYSICS, PERGAMON-ELSEVIER SCIENCE LTD, 58, 15, 1699-1709, Nov. 1996, Peer-reviwed, Temporal variations of the global lightning activity were deduced from long-term Schumann resonance (SR) continuous records. The intensities of the horizontal magnetic field component in the vicinity of the first, second, and third SR modes were monitored at Tottori observatory (35.5 degrees N, 134.33 degrees E) from 1968. Variations of the effective source-observer distance were estimated using the ratios of the intensities of individual modes. This allowed us to obtain average diurnal variations of the global lightning activity for each month over a one-year period. The results show that the distances estimated between the field-site and the effective source are very stable, while the temporal changes of the fields and the global lightning intensity derived demonstrate substantial variability. Copyright (C) 1996 Elsevier Science Ltd
Scientific journal, English

Diurnal variations of the global thunderstorm activity deduced from the Schumann resonance records
AP Nickolaenko; M Hayakawa; Y Hobara
ELECTROMAGNETIC COMPATIBILITY 1996 - THIRTEENTH INTERNATIONAL WROCLAW SYMPOSIUM, INSTITUTE TELECOMMUNICATIONS, 617-618, 1996, Peer-reviwed
International conference proceedings, English

Characteristics of mid-latitude ducts deduced by direction finding of whistlers with nose extension method.
嶋直樹; 太田健次; 北川智美; 芳原容英; 永井由佳; 早川正士
Trans. IEICE, The Institute of Electronics, Information and Communication Engineers, J79-B-II, 9, 549-556, 1996, Peer-reviwed, 中緯度ホイスラの伝搬特性,特に中緯度ホイスラダクトの諸特性を1994年8月ニュージーランド・ドニーデン(磁気緯度53.1°S : L=2.78 (Lは観測点を通る磁力線が赤道面と遭遇する地球中心からの高度を地球半径で割った値) )および1989年8月オーストラリア・セドナ(磁気緯度44.0°S : L=1.93)における約2週間にわたるホイスラ観測(水平磁界2成分,垂直電界1成分の波形観測)に基づいて調査した.多数のホイスラに対する電磁界3成分による偏波解析を行い,それぞれの観測地点上空の電離層を透過したホイスラを同定した.これらのホイスラの磁気圏伝搬路(Ln)はソース・イクステンション法を用いることによりL_n=2.84±0.06(ドニーデン),2.41±0+22(セドナ)と評価された.これらは,それぞれの観測地点上空の電離層(高度150km)のL値(L_=2.85:ドニーデン, L_=1.98:セドナ)と比べて,ドニーデンの場合はほぼ同じ,セドナの場合は0.43だけ小さいことが判明した.このことからドニーデンの場合では,従来のStrangewaysらが求めた中緯度におけるダクト伝搬ホイスラの特性とは異なり,ダクトが電離層高度まで伸びていると考えられる.しかしながら,セドナの場合はStrangewaysらの結果とほぼ一致する.これらのことはダクト構造の緯度および時間依存性を示唆しているものと考えられる.また,セドナにおける観測事実を説明するため上昇および下降ホイスラに対する種々のレイトレーシングを行った結果,セドナにて観測されたホイスラダクトの終端高度は3,500〜6,500kmであること,エンハンスメント因子は数パーセント以上であることなどがわかった.
Scientific journal, Japanese

URL

PROPAGATION CHARACTERISTICS OF WHISTLER WAVES IN THE JOVIAN IONOSPHERE AND MAGNETOSPHERE
Y HOBARA; OA MOLCHANOV; M HAYAKAWA; K OHTA
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, AMER GEOPHYSICAL UNION, 100, A12, 23523-23531, Dec. 1995, Peer-reviwed, The purpose of this paper is to carry out extensive reexamination of the propagation characteristics of unducted whistlers in the Jovian magnetosphere, In addition to the previous work on the dispersion of whistlers, our emphasis is placed on the detailed study of their amplitude variations in order to investigate the plasma structure of the magnetosphere and characteristics of causative lightlling discharges, The two-dimensional ray-tracing computations are used as before to investigate magnetospheric whistler propagation paths, but with the first attempt of estimating the whole attenuation factors (polarization effect, focusing/defocusing and interactive damping (Landau and cyclotron)). The total attenuation due to three effects is estimated, which is compared with the amplitude of whistlers observed by the Voyager spacecraft, The following conclusions are reached. (1) Some bias in magnetospheric plasma density is required to explain the high-frequency cutoff of whistlers: (2) the magnetospheric temperature is about 20 eV for the interpretation of low-frequency cutoff of whistlers, and (3) estimated total radiated power per flash is about 4.5 x 10(6) W(0 similar to 20 kHz) on the assumption of unducted propagation and nearly the same even in the case of ducted propagation.
Scientific journal, English

METHOD OF MODELING OF VLF WAVE-PROPAGATION IN THE EARTHS MAGNETOSPHERE AND UPPER IONOSPHERE
OA MOLCHANOV; OA MALTSEVA; M HAYAKAWA; Y HOBARA
RADIO SCIENCE, AMER GEOPHYSICAL UNION, 30, 5, 1597-1611, Sep. 1995, Peer-reviwed, A method of ray tracing (RT) with amplitude variations for simulating VLF wave propagation in a weakly inhomogeneous upper ionosphere and magnetosphere is discussed in detail. This ray tracing plus amplitude (RTA) technique is different from the existing ones in the selection of the most complete model with all its plasma parameters dependent on geomagnetic activity, allowance of thermal correction to the refractive index, and calculations of amplitude factors (coefficients of focusing-defocusing, polarization, and linear amplification-attenuation). The presented examples of calculations show that the introduction of the above new elements in the RT technique makes it possible to clarify the wave propagation properties and to account for numerous experimental phenomena.
Scientific journal, English

TRANSMISSION CHARACTERISTICS OF VLF ELF RADIO-WAVES THROUGH THE JOVIAN IONOSPHERE
K NAGAI; K OHTA; Y HOBARA; M HAYAKAWA
GEOPHYSICAL RESEARCH LETTERS, AMER GEOPHYSICAL UNION, 20, 22, 2435-2438, Nov. 1993, Peer-reviwed, The propagation characteristics of whistler-mode waves through the plausible profiles of the Jovian ionosphere have been investigated by means of full-wave numerical computations. There were three different profiles examined in detail: an irregular profile based on Pioneer measurements, a more-idealized smoother profile, and a smooth profile with a low-altitude ledge. The whistler transmission losses for the Pioneer profiles with several ledges are found to be extremely large in a wide frequency range from 1 to 10 kHz at both day and night, even at a high magnetic latitude. The latitudinal dependence of the transmission loss for the smooth electron density profiles corresponding approximately to the lower edge of the Pioneer profiles, is estimated such that the loss at magnetic latitude greater than 50-degrees is less than 10 dB at night and day. But the transmission loss exhibits a dramatic increase with the decrease in latitude from 30-degrees approximately 40-degrees, especially at higher frequency and at day. The presence of a possible ledge in the bottom ionosphere is found to result in an oscillatory behaviour of transmission loss due to the development of a standing wave pattern between relative density maxima. The possible utilization of these theoretical characteristics is suggested to study the coupling of lightning energy to whistlers in the Jovian magnetosphere and also lightning properties from the whistler observations by future deep spacecrafts.
Scientific journal, English

気象用二重フェーズドアレイ気象レーダとLF帯雷放電装置を用いた雲内粒子と放電過程の時系列変化
鹿倉周太郎; 菊池博史; 芳原容英; 吉川英一; 中村佳敬; 森本健志; 牛尾知雄
2023, 大気電気学会誌(Web), 17, 1, 1882-0549, 202302222914407911

Global distributions of lightning electrical energy estimated by optical observations from International Space Station
R. Kitamura; Y. Hobara; M. Sato; Y. Takahashi; T. Adachi; T. Ushio; M. Suzuki
© 2019 URSI. All rights reserved. Recent study by [1] demonstrates the remarkable similarity between the time series of lightning optical irradiance observed by high speed photometric observations in GLIMS (Global LIghtning and sprite MeasurementS on JEMEF) mission installed in the International Space Station (ISS) and current moment change estimated by groundbased ELF magnetic field measurement based on 169 lightning strokes around Japan, which also indicates the high correlation between integrated irradiance and charge moment change (Qds)., 01 Mar. 2019, 2019 URSI Asia-Pacific Radio Science Conference, AP-RASC 2019, 85068603795

国際宇宙ステーションGLIMSミッションにより観測された雷発光強度を用いた雷の電気的特性導出に関する研究
鈴木克徳; 柿沼遠方; 芳原容英; 佐藤光輝; 高橋幸弘; 足立透; 牛尾知雄; 河崎善一郎; 森本健志; 山崎敦; 鈴木睦; LINSCOTT I. R; INAN U. S
15 Nov. 2017, 大気電気学会誌, 11, 1, 102‐103, Japanese, 1882-0549, 201802261615117198

An overview of VHF lightning observations by digital interferometry from ISS/JEM-GLIMS
Takeshi Morimoto; Hiroshi Kikuchi; Mitsuteru Sato; Tomoo Ushio; Atsushi Yamazaki; Makoto Suzuki; Ryohei Ishida; Yuji Sakamoto; Kazuya Yoshida; Yasuhide Hobara; Takuki Sano; Takumi Abe; Zen Ichiro Kawasaki
© 2016 The Author(s). The Global Lightning and sprIte MeasurementS (GLIMS) mission has been conducted at the Exposed Facility of Japanese Experiment Module (JEM-EF) of the International Space Station for more than 30 months. This paper focuses on an electromagnetic (EM) payload of JEM-GLIMS mission, the very high frequency (VHF) broadband digital InTerFerometer (VITF). The JEM-GLIMS mission is designed to conduct comprehensive observations with both EM and optical payloads for lightning activities and related transient luminous events. Its nominal operation continued from November 2012 to December 2014. The extended operation followed for eight months. Through the operation period, the VITF collected more than two million VHF EM waveforms in almost 18,700 datasets. The number of VITF observations synchronized with optical signal is 8049. Active VHF radiations are detected in about 70 % of optical observations without obvious regional or seasonal dependency. Estimations of the EM direction-of-arrival (DOA) are attempted using the broadband digital interferometry. Some results agree with the optical observations, even though DOA estimation is problematic because of a very short antenna baseline and multiple pulses over a short time period, namely burst-type EM waveforms. The world's first lightning observations by means of space-borne VHF interferometry are achieved in this mission. This paper summarizes VITF instruments, the recorded VHF EM signals, and the results of DOA estimations by means of digital interferometry as a preliminary report after termination of the mission., 01 Dec. 2016, Earth, Planets and Space, 68, 1, Book review, 1343-8832, 1880-5981, 84983085442

GLIMSミッションにより観測された雷放電の発光面積・強度とその電気的特性に関する研究
柿沼遠方; 芳原容英; 牛尾知雄; 河崎善一郎; 森本健志; 佐藤光輝; 山崎敦; 鈴木睦
10 Apr. 2016, 大気電気学会誌, 10, 1, 52‐53, Japanese, 1882-0549, 201602260705513609

日本の将来のためにできること アカデミックの現場から
芳原 容英
稲城市, 2016, 稲城市生涯学習課 梨のしおり, *, Japanese, Others

JEM‐GLIMSミッションにより観測された雷発光現象と落雷電荷モーメントとの関係
柿沼遠方; 芳原容英; 牛尾知雄; 河崎善一郎; 森本健志; 佐藤光輝; 山崎敦; 鈴木睦
20 Apr. 2015, 大気電気学会誌, 9, 1, 132-133, Japanese, 1882-0549, 201502223828182410

国際宇宙ステーションGLIMSミッションにより観測されたホイスラを用いた電離層F層の電子密度推定
鈴木克徳; 柿沼遠方; 芳原容英; LINSCOTT I.R; INAN U.S; 佐藤光輝; 高橋幸弘; 牛尾知雄; 河崎善一郎; 森本健志; 山崎敦; 鈴木睦
20 Apr. 2015, 大気電気学会誌, 9, 1, 92-93, Japanese, 1882-0549, 201502296887711343

国際宇宙ステーションからの雷放電と高高度発光現象の観測
牛尾知雄; 佐藤光輝; 鈴木睦; 森本健志; 菊池博史; 菊池雅行; 足立透; 山崎敦; 高橋幸弘; INAN U.; LINSCOTT I.; 石田良平; 坂本祐二; 吉田和哉; 芳原容英; 阿部琢己; 中村正人; 織田裕久
2015, 日本気象学会大会講演予稿集, 108, 201502220137143909

国際宇宙ステーションGLIMSミッションにより観測された雷発光とホイスラを用いた電離層F層の電子密度推定
鈴木克徳; 柿沼遠方; 芳原容英; LINSCOTT Ivan; INAN Umran; 佐藤光輝; 高橋幸弘; 牛尾知雄; 河崎善一郎; 森本健志; 山崎敦; 鈴木睦
2015, 日本地球惑星科学連合大会予稿集(Web), 2015, ROMBUNNO.PEM11‐12 (WEB ONLY), Japanese, 201702229130999610

雷放電の国際宇宙ステーション搭載GLIMSミッション及び地上同時観測による大気圏・電離圏結合に関する研究
柿沼遠方; 芳原容英; 牛尾知雄; 河崎善一郎; 森本健志; 佐藤光輝; 山崎敦; 鈴木睦
18 Apr. 2014, 大気電気学会誌, 8, 1, 145-146, Japanese, 1882-0549, 201402285809424894

P320 衛星光学観測に基づく雷放電特性の導出(ポスターセッション)
足立 透; 佐藤 光輝; 牛尾 知雄; 山崎 敦; 鈴木 睦; 菊池 雅行; 高橋 幸弘; Inan Umran; Linscott Ivan; 芳原 容英; Cohen M. B.; Lu G.; Cummer S. A.; Hsu R. R.; Chen A. B.; Frey H. U.
日本気象学会, 2014, 大会講演予講集, 105, 296-296, Japanese, 110009846752, AA11552241

地震に伴う電離層擾乱の発生機構に関する研究 : 大気振動説の計算機シミュレーション
遠藤 貴士; 芳原 容英; 松村 充; 早川 正士
26 Apr. 2013, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 7, 1, 75-76, Japanese, 1882-0549, 10031170131, AA12292204

ELF帯トランジェント観測及びLF帯落雷標定ネットワークを用いた日本周辺落雷の時空間分布と電気的特性
中村 遼平; 芳原 容英; 塩川 和夫
26 Apr. 2013, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 7, 1, 91-92, Japanese, 1882-0549, 10031170139, AA12292204

高密度VLF帯送信電波観測ネットワークを用いた大地電離層擾乱に関する研究
奥埜 竜一; 芳原 容英; 岩本 真彦; 飯沼 恒一; 山田 一雅; 嶋 直樹; 塩川 和夫
26 Apr. 2013, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 7, 1, 54-55, Japanese, 1882-0549, 10031170120, AA12292204

北海道母子里で観測された地震に先行するELF帯磁場放射とULF帯磁場減少に関する研究
安江 剛広; 芳原 容英; 早川 正士; SCHEKOTOV A. Y.
26 Apr. 2013, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 7, 1, 152-153, Japanese, 1882-0549, 10031170171, AA12292204

B118 JEM-GLIMSによる宇宙からの雷・超高層放電の多波長観測(竜巻・雷,口頭発表)
足立 透; 佐藤 光輝; 牛尾 知雄; 山崎 敦; 鈴木 睦; 菊池 雅行; 高橋 幸弘; Inan Umran; Linscott Ivan; 芳原 容英
日本気象学会, 2013, 大会講演予講集, 104, 79-79, Japanese, 110009801349, AA11552241

国際宇宙ステーションからの雷放電とスプライトの国際共同観測
牛尾 知雄; 森本 健志; 佐藤 光輝; 鈴木 睦; 山崎 敦; 芳原 容英; 菊地 雅行; 高橋 幸弘; 石田 良平; 坂本 祐二; 吉田 和哉; 阿部 琢美; 河崎 善一郎
15 Nov. 2012, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 6, 2, 82, Japanese, 1882-0549, 10031128631, AA12292204

ELFトランジェント及びLF帯落雷標定ネットワークを用いた日本周辺落雷の電気的特性
中村 遼平; 芳原 容英; 塩川 和夫; 早川 正士
15 Nov. 2012, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 6, 2, 76-77, Japanese, 1882-0549, 10031128628, AA12292204

国際宇宙ステーションからの雷放電とスプライトの国際共同観測
牛尾知雄; 森本健志; 佐藤光輝; 鈴木睦; 山崎敦; 芳原容英; 菊地雅行; 高橋幸弘; INAN Umran; 石田良平; 坂本祐二; 吉田和哉; 阿部琢美; 河崎善一郎
2012, 大気電気学会誌, 6, 2, 1882-0549, 201202222321410014

3D-FDTD法を用いた中間圏発光現象に伴う電離層擾乱についての数値解析
岩本真彦; 芳原容英; 成毛亮介; 大津山卓哉; 太田健次; 早川正士
2012, 大気電気学会誌, 6, 1, 1882-0549, 201202249599482445

Lightning and sprite observation from international space station
Tomoo Ushio; Mitsuteru Sato; Takeshi Morimoto; Makoto Suzuki; Hiroshi Kikuchi; Atsushi Yamazaki; Yukihiro Takahashi; Yasuhide Hobara; Umran Inan; Umran Inan; Ivan Linscott; Ivan Linscott; Yuji Sakamoto; Yuji Sakamoto; Ryohei Ishida; Ryohei Ishida; Masavuki Kikuchi; Masavuki Kikuchi; Kazuya Yoshida; Kazuya Yoshida; Zen Ichiro Kawasaki
Lightning and sprite measurement sensors on the International Space Station (ISS) are introduced in this paper. Lightning is an electrical discharge which neutralizes the charge inside thunderstorm. In the early 1990s, optical transient luminous events (TLEs) occurring just above the thunderstorm were firstly reported by the US scientists and are associated with positive cloud-to-ground discharges with a large amount of charge. Though the luminous events so-called sprite, elves and jets have been investigated by numerous researchers all over the world based mainly on the ground observations, some important problems have not been fully understood yet such as generation mechanisms of columniform fine structure and horizontal offset of some sprites from the parent lightning discharges. In the JEM-GLIMS mission, observations from our synchronized sensors are going to shed light on above-mentioned unsolved problems regarding TLEs as well as causative lighting discharges. Our goals are (1) to detect and locate lightning and sprite within storm scale resolution over a large region of the Earth's surface along the orbital track of the ISS without any bias, (2) to clarify the generation mechanism of sprite, and (3) to identify the occurrence conditions of TLEs. © 2011 The Institute of Electrical Engineers of Japan., 28 Feb. 2011, IEEJ Transactions on Fundamentals and Materials, 131, 16-20, 0385-4205, 79951903581

中間圏発光現象に伴うVLF帯送信電波擾乱の数値解析
岩本真彦; 芳原容英; 大津山卓哉; 太田健次; 早川正士
2011, 大気電気学会誌, 5, 1, 1882-0549, 201102255096906798

3次元空間における中間圏発光現象に伴う電離層擾乱についての数値解析
岩本真彦; 芳原容英; 成毛亮介; 大津山卓哉; 太田健次; 早川正士
2011, 大気電気学会誌, 5, 2, 1882-0549, 201102236805751227

Lightning and Sprite Observation from International Space Station
USHIO Tomoo; SATO Mitsuteru; MORIMOTO Takeshi; SUZUKI Makoto; KIKUCHI Hiroshi; YAMAZAKI Atsushi; TAKAHASHI Yukihiro; HOBARA Yasuhide; INAN Umran; ISHIDA Ryohei; KAWASAKI Zen-Ichiro
01 Nov. 2010, 電気学会研究会資料. EMC, 電磁環境研究会, 2010, 29, 1-4, Japanese, 10027631055

A209 国際宇宙ステーションからの雷放電と高高度発光現象の観測(GLIMS)(降水システムI,一般口頭発表)
牛尾,知雄; 森本,健志; 佐藤,光輝; 鈴木,睦; 山崎,敦; 芳原,容英; 菊地,雅行; 高橋,幸弘; 石田,良平; 坂本,祐二; 吉田,和哉; 阿部,琢美; 河崎,善一郎
日本気象学会, 30 Apr. 2010, 大会講演予講集, 97, 52, Japanese, 110007728906, AA11552241

中間圏発光現象に伴う電離層擾乱のシミュレーションに関する研究
藤井裕之; 芳原容英; 早川正士; 松戸悠; 大津山卓哉; 太田健次
2010, 大気電気学会誌, 4, 1, 1882-0549, 201002283956491805

国際宇宙ステーションからの雷放電・スプライト観測計画 : JEM-GLIMSミッション
佐藤 光輝; 牛尾 知雄; 森本 健志; 高橋 幸弘; 芳原 容英; 菊池 雅行; 鈴木 睦; 山崎 敦; 阿部 琢美; 吉田 和哉; 坂本 祐二; 奥山 圭一; 石田 良平; 河崎 善一郎
30 Oct. 2009, 大気電気学会誌 = / Society of Atmospheric Electricity of Japan, 3, 2, 60-61, Japanese, 1882-0549, 10025594045, AA12292204

GLIMSミッションに期待される科学~雷放電~
森本健志; 牛尾知雄; 佐藤光輝; 高橋幸弘; INAN Umran; 芳原容英; 菊池雅行; 鈴木睦; 山崎敦; 阿部琢美; 吉田和哉; 坂本祐二; 奥山圭一; 石田良平; 河崎善一郎
2009, 大気圏シンポジウム・講演集(Web), 23rd, 201002206032871780

GLIMSミッションに期待される科学:地球ガンマ線現象
高橋幸弘; 嘉瀬浩美; 牛尾知雄; 森本健志; 佐藤光輝; INAN Umran; 芳原容英; 菊池雅行; 鈴木睦; 山崎敦; 阿部琢美; 吉田和哉; 坂本祐二; 奥山圭一; 石田良平; 河崎善一郎
2009, 大気圏シンポジウム・講演集(Web), 23rd, 201002227229213854

JEM-GLIMSミッションの概要
牛尾知雄; 鈴木睦; 佐藤光輝; 森本健志; 高橋幸弘; 芳原容英; 菊池雅行; INAN Umran; 山崎敦; 阿部琢美; 河崎善一郎
2009, 大気圏シンポジウム・講演集(Web), 23rd, 201002255880876164

GLIMSミッションに期待される科学:高高度発光現象
佐藤光輝; 牛尾知雄; 森本健志; 高橋幸弘; INAN Umran; 芳原容英; 菊池雅行; 石田良平; 吉田和哉; 坂本祐二; 奥山圭一; 河崎善一郎; 鈴木睦; 山崎敦; 阿部琢美
2009, 大気圏シンポジウム・講演集(Web), 23rd, 201002295224478510

ELF transientsを用いた世界雷放電分布の導出
山下幸三; 大津山卓哉; 芳原容英; 関口美菜子; 松戸悠; 早川正士
2007, 大気電気学会誌, 1, 1, 1882-0549, 200902248935797253

雷放電に伴う発光現象および電磁放射について
大津山卓哉; 芳原容英; 早川正士
1999, 大気電気研究, 54, 0286-3405, 200902136629950118

Preliminary result of Japan and Australia joint campaign. VLF/ELF wave.
大津山卓哉; 土谷敬亮; 芳原容英; 早川正士
1997, 大気電気研究, 51, 0286-3405, 200902131991844570

これからのＥＭＣ
芳原容英
Others, Japanese, Joint work, 科学情報出版, 05 Jan. 2019

ユニーク＆エキサイティングサイエンス
梶谷誠; 芳原容英
Japanese, Joint work, 地震の予測は可能か？電波の威力！, 近代科学社, Mar. 2013

Geomatics, Natural Hazards and Risk volume4,Issue3,2013
English, Joint work, The lower ionospheric perturbation as a precursor to the 11 March 2011 Japan earthquake, Taylor & Francis, Jan. 2013

Lighting effects in the mesosphere and ionosphere
M. Hayakawa; Y. Hobara; T.Suzuki
English, Joint work, The Institution of engineering and technology, Jan. 2012

地震に関連するULF帯磁場データの統計的解析、「地震予知研究の最前線」、早川正士編
芳原容英; 山口弘輝; 早川正士
Japanese, Joint work, 日本専門図書出版㈱, 2012

VHF帯電波を用いた地震予知の可能性、「地震予知研究の最前線」、早川正士編
安田好広; 芳原容英; 早川正士
Japanese, Joint work, 日本専門図書出版㈱, 2012

VLF/LF送信局電波を用いた電離圏擾乱観測に基づく地震予知研究、「地震予知研究の最前線」、早川正士編
早川正士; 芳原容英
Japanese, Joint work, 日本専門図書出版㈱, 2012

Lightning Electromagnetics
Y.Hobara; M. Hayakawa
English, Joint work, Chapter 16:Lightning effects in the mesosphere and ionosphere Chapter 17:The effects of lightning on the ionosphere/magnetosphere, IET, 2012

Sprites, Elves and Intensive Lightning Discharges
Y. Hobara; M. Hayakawa; E. Williams; R. Boldi; E. Downes
English, Joint work, Location and electrical properties of sprite-producing lightning from a single ELF site, Springer, 2006

Introduction to Atmospheric Electricity
芳原容英
Japanese, Joint work, 3.7節 空電関連現象, Corona Pub. Comp., 2003

Seismo Electromagnetics: Lithosphere-Atmosphere-Ionosphere Coupling
H. C. Koons; J. L. Roeder; Y. Hobara; M. Hayakawa; A. C. Fraser-Smith
English, Joint work, Statistical analysis of the data from ULF sensors at Seikoshi Station, TERRAPUB, 2002

Seismo Electromagnetics: Lithosphere-Atmosphere-Ionosphere Coupling
Y. Hobara; H. C. Koons; J. L. Roeder; H. Yamaguchi; M. Hayakawa
English, Joint work, New ULF/ELF observation in Seikoshi, Izu, Japan, and the precursory signal in relation with recent large seismic events near Izu, TERRAPUB, 2002

Monitoring and prediction of terrestrial and space environments using natural and man-made electromagnetic noises
Y. Hobara
Invited oral presentation, English, URSI-JRSM2022, International conference
02 Sep. 2022

Modeling Atmosphere-Ionosphere Coupling during Typhoon 15 Using FDTD Method
A. D. Setiawan; Y.Hobara; H. Kikuchi
Invited oral presentation, English, URSI-JRSM2022, International conference
02 Sep. 2022

Observations of Precipitation Cores with X-band Dual Polarized Phased Array Weather Radar and LF Band Lightning Location System
H. Kikuchi; E. Yoshikawa; Y. Nakamura; T. Morimoto; T. Ushio; Y. Hobara
Invited oral presentation, English, URSI-JRSM2022, International conference
02 Sep. 2022

Thunderstorms and Total Lightning Characteristics Causing Heavy Precipitation in Japan: A Case Study
D. Mondal; Y. Hobara; H. Kikuchi; J. Lapierre
Invited oral presentation, English, URSI-JRSM2022, International conference
02 Sep. 2022

Variations of the Effective Height of the Lower Ionosphere according to the Results of Tweek-Atmospherics Measurements in the Northern and Southern Hemispheres
A. Shvets; V. Ivanov; Y. Hobara; O. Koloskov; Y. Yampolsky
Invited oral presentation, English, URSI-JRSM2022, International conference
02 Sep. 2022

Lower Ionospheric Fluctuations and Atmospheric Electric Field Immediately around Earthquake
K. Misu; M. Watanabe; H. Kikuchi; Y. Hobara
Invited oral presentation, English, URSI-JRSM2022, International conference
01 Sep. 2022

Statistical analysis of the Atmospheric Electric Field Fluctuations associated with Earthquakes in Japan
M. Watanabe; Y. Hobara; H. Kikuchi; R. Miyajima
Invited oral presentation, English, URSI-JRSM2022, International conference
01 Sep. 2022

Atmospheric Electric Field Anomaly Observed Immediately Before and After Earthquakes
Y. Hobara
Oral presentation, English, ICAE2022, ICAE2022, Tel Aviv, Israel, International conference
21 Jun. 2022

LF帯雷放電標定装置と二重偏波フェーズドアレイ気象レーダを用いた積乱雲の発達過程の観測
菊池 博史; 及川 夏依; 芳原 容英; 中村 佳敬; 吉川 栄一; 森本 健志; 牛尾 知雄
Oral presentation, Japanese, 日本地球惑星科学連合2022年大会, 日本地球惑星科学連合, 幕張、千葉
02 Jun. 2022

Modeling Lower Ionospheric Perturbations during Heavy Precipitation Using 2D FDTD Method
A. D. Setiawan; Y. Hobara
Oral presentation, Japanese, 日本地球惑星科学連合2022年大会, 日本地球惑星科学連合, 幕張、千葉
02 Jun. 2022

Modeling Lower Ionospheric Perturbations During Typhoons 15 and 19 Using 2D FDTD Method
A. D. Setiawan; Y. Hobara; S. Hirai
Oral presentation, English, AT-AP-RASC 2022, AT-AP-RASC 2022, Gran Canaria, Spain, International conference
01 Jun. 2022

Lower Ionospheric Perturbations Associated with Proton Aurora using Numerical Simulation of Subionospheric VLF Transmitter Signals
Y. Hobara; H. Nomoto; A. Hirai
Oral presentation, English, AT-AP-RASC 2022, AT-AP-RASC 2022, Gran Canaria, Spain, International conference
31 May 2022

Thunderstorms and total lightning characteristics causing heavy precipitation in Japan
D. Mondal; Y. Hobara; H. Kikuchi
Oral presentation, Japanese, 日本地球惑星科学連合2022年大会, 日本地球惑星科学連合, 幕張、千葉
25 May 2022

機械学習を用いた宇宙電磁環境の監視と予測
芳原 容英
Oral presentation, Japanese, 第7回データアントレプレナーカンファレンス - データサイエンスと宇宙科学
17 Jan. 2022

プロトンオーロラに伴う下部電離層擾乱のモデリングによるVLF帯送信電波異常の数値計算
野本博樹; 芳原 容英; 土屋史紀; 平井あすか
Oral presentation, Japanese, 第100回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2022

気象用二重偏波フェーズドアレイ気象レーダとLF帯雷放電標定装置を用いた夏季積乱雲の観測
菊池博史; 及川夏依; 芳原容英; 中村佳敬; 吉川栄一; 森本健志; 牛尾知雄
Oral presentation, Japanese, 第100回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2022

地震直前後に観測された大気電界異常
芳原容英; 宮島理紗; 渡辺真子; 松木翔; 菊池博史
Oral presentation, Japanese, 日本地震予知学会第8回学術講演会, 日本地震予知学会, 東京
25 Dec. 2021

VLF帯送信電波伝搬の数値計算を用いたプロトンオーロラに伴う下部電離層擾乱のモデリング
野本博樹; 芳原 容英; 土屋史紀; 平井あすか
Oral presentation, Japanese, EMCJ研究会, 電子情報通信学会, オンライン会場
08 Dec. 2021

Global Distributions of Lightning Electrical Properties Obtained from International Space Station
Y. Hobara; H. Kikuchi; R. Kitamura; M. Sato; Y. Takahashi; T. Adachi; T. Ushio; M. Suzuki
Oral presentation, English, URSI GASS 2021, International conference
30 Aug. 2021

Total Lightning Activity associated with Extreme Meteorological Events in Japan a View from X-band Radar and Meteorological Satellite
Y. Hobara; H. Kikuchi; R. Aoyagi; M. Stock
Oral presentation, English, URSI GASS 2021, International conference
30 Aug. 2021

Multi-Point Simultaneous Prediction Model for Electron Flux at Geostationary Orbits
H. Nomoto; Y. Hobara; H. Kikuchi; H. Iibuchi; M. Balikhin
Oral presentation, English, URSI GASS 2021, International conference
30 Aug. 2021

Detecting Ionospheric Anomalies before Earthquakes by Machine Learning Technique
Y. Hobara; K. Matsuki; H. Santosa
Oral presentation, English, URSI GASS 2021, International conference
30 Aug. 2021

Monitoring and predicting terrestrial and space environments using electromagnetic methods
Y. Hobara
Invited oral presentation, English, URSI GASS 2021, Invited, International conference
30 Aug. 2021

Relationship between Atmospheric Electric Fields and Lower Ionospheric Disturbances Associated with Earthquakes
Y. Hobara; K. Matsuki; M. Watanabe; H. Kikuchi; A. Setiwan
Oral presentation, English, IAGA- IASPEI 2021 Virtual conference, IAGA- IASPEI 2021 Virtual conference, India, International conference
26 Aug. 2021

Spatio-temporal Distributions of Lightning Stroke Charge using ELFand Meteorological Data
Y. Hobara
Keynote oral presentation, English, InECCE 2021, UMP Malaysia, Malaysia, International conference
23 Aug. 2021

Spatio-temporal characteristics of energetic lightning in Southeast Asia: Preliminary statistical results
S. Akama; Y. Hobara; M. A. Izzani; C. Gomes; K. Shiokawa; S. Hirai; H. Kikuchi; M.Stock
Oral presentation, English, InECCE 2021, UMP Malaysia, Malaysia, International conference
23 Aug. 2021

マルチパラメータフェーズドアレイ気象レーダを用いた3次元降水コアトラッキング手法の検討
浅井 啓太郎; 菊池 博史; 芳原 容英; 牛尾 知雄
Oral presentation, Japanese, 日本地球惑星科学連合2021年大会
06 Jun. 2021

台風に伴う大規模気象擾乱の電離圏への結合過程に関する研究
平井 周; 芳原 容英; 菊池 博史; M. Stock
Oral presentation, Japanese, 日本地球惑星科学連合2021年大会
06 Jun. 2021

LF帯3次元雷放電標定装置と二重偏波フェーズドアレイ気象レーダを用いた夏季積乱雲の観測事例
菊池 博史; 亀井 悠平; 中村 佳敬; 吉川 栄一; 森本 健志; 牛尾 知雄; 芳原 容英
Oral presentation, Japanese, 日本地球惑星科学連合2021年大会
06 Jun. 2021

東南アジアにおけるエネルギー別落雷の時空間特性に関する初期解析
赤間 俊介; 平井 周; 芳原 容英; 菊池 博史; A. Mohamed; C. Gomes; 塩川 和夫; M. Stock
Oral presentation, Japanese, 日本地球惑星科学連合2021年大会
06 Jun. 2021

複合電波観測を用いた台風に伴う大気圏と電離圏の関連性に関連する研究
平井周; 芳原容英; 菊池博史; マイケルストック
Oral presentation, Japanese, 電子情報通信学会 環境電磁工学研究会, 電子情報通信学会, オンライン開催
16 Apr. 2021

二十偏波フェーズドアレイレーダを用いた粒子判定結果とTotal Lightning Networkによる雷観測結果の比較
及川夏依; 菊池博史; 芳原容英; 牛尾智雄
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

雷嵐特性のアンサンブル学習を用いた突風発生の予測
宮下志保; 平井周; 芳原容英; 菊池博史; Michael Stock
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

機械学習を用いた静止軌道上における電子フラックスの多点同時予測モデルの構築と評価
野本博樹; 芳原容英; 菊池博史; 飯淵隼人; Michael Balikhin
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

二重偏波フェーズドアレイ気象レーダの偏波パラメータに関する精度検証
浅井啓太郎; 菊池博史; 牛尾知雄; 芳原容英
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

台風に由来する大気圏-電離圏結合に関する研究
平井周; 星野龍一; 芳原容英; 菊池博史; M. Stock
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

関東圏における3次元雷放電標定装置を用いた初期観測結果
亀井悠平; 菊池博史; 芳原容英; 中村佳敬; 吉川栄一; 森本健志; 牛尾知雄
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

東南アジアにおける落雷エネルギー別雷嵐の時空間特性
赤間俊介; 平井周; 芳原容英; 菊池博史; Amir Izzani Mohamed; Chandima Gomes; 塩川和夫; Michael Stock
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

地震に関連する大気電界変動
芳原容英; 宮島理紗; 渡辺真子; 松木翔; 菊池博史
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

地震に関連する大気電界変動
芳原容英; 宮島理紗; 渡辺真子; 松木翔; 菊池博史
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

北海道女満別における地震に伴う大気電界変動の調査
渡辺真子; 芳原容英; 菊池博史; 松木翔
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

地震に伴う大気電界と下部電離層擾乱の関連性に関する研究
松木翔; 宮島理紗; 芳原容英; 菊池博史
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

二重偏波フェーズドアレイ気象レーダを用いた2019年台風15号の3次元観測
菊池博史; 牛尾知雄; 芳原容英
Oral presentation, Japanese, 第99回日本大気電気学会, 日本大気電気学会, オンライン会場
08 Jan. 2021

Monitoring Energetic Lightning in Southeast Asia using ELF magnetic field observations in Malaysia
Y. Hobara; H. Kikuchi; C. Gomes; A. Mohamed; M. Stock; K. Shiokawa
Poster presentation, English, VERSIM Virtual Meeting
17 Nov. 2020

F- Layer Critical Frequency deduced from Lightning Whistlers
S.Hirai; Y.Hobara; S Kanazawa; J.L.Pinçon
Poster presentation, English, VERSIM Virtual Meeting
17 Nov. 2020

F- Layer Critical Frequency deduced fromLightning Whistlers
S. Hirai; Y. Hobara; S. Kanazawa; J. L. Pinçon
Oral presentation, English, Versim2020, International conference
24 Mar. 2020

Monitoring Energetic Lightning in Southeast Asia using ELF magnetic field observations in Malaysia
Y. Hobara; H. Kikuchi; C. Gomes; A. Mohamed; M. Stock; K. Shiokawa
Oral presentation, English, International conference
24 Mar. 2020

Response of the Mesosphere and Lower Ionosphere to an Extremely Severe Cyclone "Fani" of May
S. Pal; S. Sarkar; S. K. Midya; S. K. Mondal; Y. Hobara
Oral presentation, English, Versim2020, International conference
24 Mar. 2020

台風 15 号および 19 号の発生から消滅までの雷特性
Teoh Che Kok; 芳原容英; 平井周; 菊池博史
Oral presentation, Japanese, 第98回日本大気電気学会, 日本大気電気学会, 静岡
10 Jan. 2020

Evolution of total lightning activity associated with severe thunderstorms in Japan characterized by a high speed ground-based radar and meteorological satellite
Y. Hobara; H. Kikuchi; R. Aoyagi; M. Stock
Oral presentation, English, American Geophysical Union (AGU) Fall Meeting, San Francisco, International conference
09 Dec. 2019

Lightning Applications to Natural Hazard Mitigation
Y. Hobara
Oral presentation, English, 2019 URSI-Japan Radio Science Meeting, URSI-JRSM, UEC, Tokyo, International conference
05 Sep. 2019

Lightning Applications to Natural Hazard Mitigation
Y. Hobara
Oral presentation, Japanese, 2019 URSI-Japan Radio Science Meeting, UEC,Tokyo Japan
05 Sep. 2019

Global Distributions of Lightning Electrical Characteristics Estimated by Optical Observation from International Space Station
R. Kitamura; Y. Hobara; H. Kikuchi; M. Sato; Y. Takahashi; T. Adachi; T. Ushio; M. Suzuki
Oral presentation, Japanese, 2019 URSI-Japan Radio Science Meeting, UEC,Tokyo Japan
05 Sep. 2019

Characteristics of Optical Lightning Waveforms Observed by Photometers on the International Space Station Optical Observation from International Space Station
H. Kikuchi; Y. Hobara; M. Sato; T. Morimoto
Oral presentation, Japanese, 2019 URSI-Japan Radio Science Meeting, UEC,Tokyo Japan
05 Sep. 2019

Improving F-layer Critical frequency deduced from Fractional Hop Lightning Whistlers
S. Hirai; Y. Hobara; J.L. Pincon; M. Parrot
Oral presentation, Japanese, 2019 URSI-Japan Radio Science Meeting, UEC,Tokyo Japan
05 Sep. 2019

Detecting Ionospheric Anomalies before Earthquakes by Machine Learning Technique
K. Matsuki; Y. Hobara; H. Santosa
Oral presentation, Japanese, 2019 URSI-Japan Radio Science Meeting, UEC,Tokyo Japan
05 Sep. 2019

ELF transient observations to mitigate damage to power grid systems
Y. Hobara
Keynote oral presentation, English, 4th International Symposium on Lightning Research (ISLR2019), Invited, Universiti Tenaga Nasional, Selangor, Malaysia, International conference
29 Aug. 2019

国際宇宙ステーションからの光学観測に基づく世界雷の空間分布と電気的特性に関する研究
北村隆之介; 芳原容英; 菊池博史; 佐藤光輝; 高橋幸弘; 足立透研; 牛尾知雄; 鈴木睦
Oral presentation, Japanese, 環境電磁工学研究会 (EMCJ), 電子情報通信学会
18 Jul. 2019

Lightning Charge Moment Changes Deduced from Highly Sensitive ELF Magnetic Field Observations in Southeast Asia
Y. Hobara
Oral presentation, English, EMC Sapporo &APEMC2019, 電子情報通信学会 2019年環境電磁工学国際シンポジウム組織委員会, Sapporo, International conference
06 Jun. 2019

熱帯降雨観測衛星TRMMからの雷の光学観測を用いた雷の電気エネルギー導出に関する研究
平田 浩大; 芳原 容英; 菊池 博史
Oral presentation, Japanese, Japan Geoscience Union Meeting 2019, 日本地球惑星科学連合2019年大会, 千葉, Domestic conference
28 May 2019

雷起源ホイスラー波を用いた電離層F層電子密度の推定における精度向上の検討
平井 周; 金澤 璋吾; 芳原 容英; J. L. Pincon
Oral presentation, Japanese, Japan Geoscience Union Meeting 2019, 日本地球惑星科学連合2019年大会, 千葉, Domestic conference
28 May 2019

非線形自己回帰ニューラルネットワークを用いた地震に先行する下部電離層異常の検出
松木 翔; 飯淵 隼人; H. Santosa; 芳原 容英; M. Balikhin
Oral presentation, Japanese, Japan Geoscience Union Meeting 2019, 日本地球惑星科学連合2019年大会, 千葉, Domestic conference
28 May 2019

日本国内での豪雨に伴う雷放電を用いた降水量の推定
小川 哲也; 芳原 容英; 岩崎 博之; S. Heckman; M. Stock
Oral presentation, Japanese, Japan Geoscience Union Meeting 2019, 日本地球惑星科学連合2019年大会, 千葉, Domestic conference
28 May 2019

Lightning applications to severe weather and power grid systems
Y. Hobara
Invited oral presentation, English, National Conference on Severe Weather (NCSW-2019), Invited, Kolkata University, Kolkata, India, International conference
17 Mar. 2019

Lightning applications to severe weather and power grid systems, National Conference on Severe Weather
Y. Hobara
Oral presentation, English, National Conference on Severe Weather (NCSW-2019), Kolkata University, Kolkata, India, International conference
17 Mar. 2019

Prediction of D Region Characteristics using Nonlinear System Identification Technique applied to VLF/LF Transmitter Data
Y. Hobara; H. Santosa
Invited oral presentation, English, 2019 URSI AP-Rasc, International conference
14 Mar. 2019

Total Lightning Activities during Recent Extreme Weather Events in Japan
Y. Hobara; S. Kono; T. Ogawa; S. Heckman; M. Stock
Oral presentation, English, 2019 URSI AP-Rasc, 2019 URSI AP-Rasc, New Delhi, India, International conference
14 Mar. 2019

Global distributions of Lightning Electrical Energy Estimated by Optical Observations from International Space Station
R. Kitamura; Y. Hobara; M. Sato; Y. Takahashi; T. Adachi; T. Ushio; M. Suzuki
Poster presentation, English, 2019 URSI AP-Rasc, 2019 URSI AP-Rasc, New Delhi, India, International conference
14 Mar. 2019

Lightning Charge Estimation over Eastern Part of Japan by ELF and LLS Observations
Y. Hobara; R. Kitamura; T. Narita; D. Ohta; T. Tsuya
Poster presentation, English, 2019 URSI AP-Rasc, URSI AP-Rasc, New Delhi, International conference
11 Mar. 2019

Lightning application to extreme weather
Y. Hobara
Invited oral presentation, English, 6th International Conference on Signal Processing and Integrated Networks, Invited, SPIN2019, Delhi, India, International conference
07 Mar. 2019

東南アジアにおける高感度ＥＬＦ帯磁場観測を用いた落雷の電気的特性の導出（初期解析結果）
芳原容英; C. Gomes; A. I. Mohamed; 塩川和夫; M. Stock; 津田卓雄
Oral presentation, Japanese, 第97回日本大気電気学会, Domestic conference
11 Jan. 2019

国際宇宙ステーションからの光学観測により推定された落雷電荷モーメントの全球分布
北村隆之介; 芳原容英; 菊池博史; 佐藤光輝; 高橋幸弘; 足立透; 牛尾知雄; 鈴木睦
Oral presentation, Japanese, 第97回日本大気電気学会, Domestic conference
11 Jan. 2019

雷の電波を観測し、地震や竜巻、宇宙転記の予測を目指す
芳原容英
Public discourse, Japanese, 目黒会北陸支部総会, 一般社団法人目黒会
17 Nov. 2018

電波で地球や宇宙環境を探る・予測する
芳原容英
Public discourse, Japanese, 平成30年度目黒会東海支部・総会, 目黒会東海支部
03 Nov. 2018

Lightning application to extreme weather and power grid systems
Y. Hobara
Invited oral presentation, English, National Seminar on Innovation, Technology and Applications (SENITIA), Bengkulu, Indonesia, International conference
27 Sep. 2018

Lightning application to extreme weather and power grid systems
Y. Hobara
Invited oral presentation, English, Seminar Nasional Inovasi, Teknologi dan Aplikasi, Univ.of Bengkulu, Indonesia, http://senitia.ft.unib.ac.id/, International conference
27 Sep. 2018

Monitoring and prediction of Earth's environment using electromagnetic method
Y. Hobara
Oral presentation, English, Seminar Nasional Inovasi, Teknologi dan Aplikasi, Univ.of Bengkulu, Indonesia, http://senitia.ft.unib.ac.id/, International conference
27 Sep. 2018

Monitoring and forecasting the Earth's and space environments by multi-frequency radio wave observations
Y. Hobara
Oral presentation, English, 50th Anniversary International Symposium of Center for Space Science and Radio Engineering (SSRE), Space Science and Radio Engineering, UEC
26 Jun. 2018

Monitoring and forecasting the Earth's and space environments by multifrequency radio wave observations
Y. Hobara
Public symposium, English, 50th Anniversary International Symposium of Center for Space Science and Radio Engineering
25 Jun. 2018

Characteristics of total lightning associated with recent hazardous weather events in Japan
Y. Hobara; S. Kono; T. Ogawa; S. Heckman; M. Stock; C. Liu
Oral presentation, English, ICAE2018, International conference
22 Jun. 2018

Lightning characteristics with charge moment change over eastern part of Japan by ELF and LLS observations, ICAE2018, Nara, Japan
Y. Hobara; J. Yamashita; R. Murai; T. Narita; H. Mitsuzuka
Oral presentation, English, ICAE2018, International conference
22 Jun. 2018

Statistical study of the relationship between total lightning and heavy rainfall, ICAE2018, Nara, Japan
T. Ogawa; Y. Hobara; H. Iwasaki; S. Heckman; M. Stock
Oral presentation, English, ICAE2018, International conference
22 Jun. 2018

Gamma-ray Flash from a Winter Thunderstorm in Japan, ICAE2018, Nara, Japan
M. Stock; Z.Kawasaki; Y. Hobara; T. Ushio; D. Wang; S. Heckman; S. A. Cummer; X. Shao; J. R. Dwyer
Oral presentation, English, ICAE2018, International conference
22 Jun. 2018

Nonlinear prediction model of ionospheric foF2 variability
H. Santosa; Y. Hobara
Oral presentation, English, Japan Geoscience Union Meeting 2018, Domestic conference
22 May 2018

Boynton RichardPredication of ULF geomagnetic field based on nonlinear system identification approach
H. Iibuchi; H. Santosa; Y. Hobara; M. Balikhin
Oral presentation, English, Japan Geoscience Union Meeting 2018, Domestic conference
22 May 2018

日本国内の突風現象を伴う積乱雲におけるトータル雷の特性に関する研究
甲野槙太郎; 芳原容英; S. Heckman; M.Stock
Oral presentation, Japanese, Japan Geoscience Union Meeting 2018, Domestic conference
22 May 2018

Accuracy verification of lightning charge moment and lightning charge height remotely estimated by ELF observations using lightning current measurements at wind turbine
村井峻; 芳原容英; 箕浦史登; 吉田遼大郎; 三塚洋明; 成田知巳; 石井勝; 斎藤幹久; 夏野大輔
Oral presentation, English, Japan Geoscience Union Meeting 2018, Domestic conference
22 May 2018

VLF/LF帯電波の多点観測及び3次元FDTD法を用いた金環日食に伴う電波伝搬特性の解明に関する研究
金澤璋吾; 芳原容英; 安藤芳晃
Oral presentation, Japanese, Japan Geoscience Union Meeting 2018, Domestic conference
22 May 2018

Modeling and predictions of D region characteristics using nonlinear autoregression and neural network
Y. Hobara
Invited oral presentation, English, Versim2018, Apatity, Russia, International conference
26 Mar. 2018

Lightning electrical property deduced from high speed photometric observations from space station
Y. Hobara
Invited oral presentation, English, Versim2018, Apatity, Russia, International conference
26 Mar. 2018

極超長波を用いた雷関連電磁気現象の観測と応用
芳原容英
Invited oral presentation, Japanese, 研究フォーラム 電力システムに対する雷・自然災害と環境問題に関する研究, 電気学会, Domestic conference
10 Mar. 2018

ELF帯磁界の国内2点同時観測を用いた落雷位置および電荷モーメント推定精度に関する研究
村井崚; 芳原容英; 三塚洋明; 皆川郁靖; 成田知巳; M. Stock; S. Heckman
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

ELF帯トランジェントを用いた関東周辺における落雷電荷量推定に関する研究
小林瑞貴; 村井崚; 芳原容英; 三塚洋明; 皆川郁靖; 成田知巳
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

DEMETER衛星で観測された雷起源ホイスラの自動抽出により推定されたF2層最大電子密度の世界空間分布
Y. Girma; 鈴木克徳; 芳原容英; M. Parrot; J. L Pincon
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

日本で発生した巨大ジェットに伴う下部電離層擾乱と電荷モーメントに関する研究
河内健太郎; 芳原容英; 鈴木智幸; 鴨川仁
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

突風現象を伴う積乱雲におけるトータル雷の特性に関する研究
甲野慎太郎; 芳原容英; S. Heckman; M. Stock; C. Liu
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

日本国内で観測されたトータル雷と激しい降水との相関関係の調査
小川哲也; 芳原容英; 岩崎博之; M. Stock; S. Heckman
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

Richard Boynton, 非線形システム同定手法を用いたULF帯磁場時間変動のモデリング及び変動要因の考察
飯淵隼人; H. Santosa; 芳原容英; M. Balikhin
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

非線形自己回帰ニュートラルネットワークを用いた国内における下部電離層の時間変動のモデリング
岡庭章浩; H. Santosa; 芳原容英
Oral presentation, Japanese, 第96回日本大気電気学会, Domestic conference
06 Jan. 2018

One day prediction of nighttime VLF amplitudes using nonlinear autoregression and neural network modeling
H. Santosa; Y. Hobara
Oral presentation, English, 日本地震予知学会 第４回学術講演会, 日本地震予知学会, 電気通信大学
26 Dec. 2017

Total lightning characteristics of recent hazardous weather events in Japan
Y. Hobara; S. Kono; T. Ogawa; S. Heckman; M. Stock; C.e Liu
Oral presentation, English, American Geophysical Union (AGU) Fall Meeting, International conference
12 Dec. 2017

Lightning charge moment changes estimated by high speed photometric observations from ISS
S. Kono; K. Suzuki; Y. Hobara; M. Sato; Y. Takahashi; T. Ushio; M. Suzuki
Oral presentation, English, American Geophysical Union (AGU) Fall Meeting, New Orleans, International conference
12 Dec. 2017

Ashwini Kumar Sinha and Yuri Yampolski, Verification of a Schumann Resonance Inversion Method for Global Lightning Activity in Absolute Units
E. R. Williams; A. Guha; Y. Liu; R. A Boldi; E. Pracser; R. Said; G. Satori; T. Bozoki; J. Bor; M. Atkinson; C. Beggan; S. Cummer; F. Lyu; B. Fain; Y. Hobara; K. Alexander; A. Kulak; R. McCraty; J. Mlynarczyk; J. Montanya; R. C. Moore; M. Neska; P. Ortega; C. G. Price; R. Rawat; M. Sato; A. Sinha; Y. Yampolski
Oral presentation, English, American Geophysical Union (AGU) Fall Meeting, Americal Geophysical Union (AGU), New Orleans, USA, International conference
11 Dec. 2017

風力発電施設への着雷事例を用いたＥＬＦ帯電磁波観測により遠隔推定された落雷電荷モーメントおよび落雷電荷量推定精度の検証
村井崚; 芳原容英; 山下純平; 吉田遼大郎; 箕浦史登; 三塚洋明; 太田浩; 成田知巳
Oral presentation, Japanese, 電気学会 平成２９年度電力・エネルギー部門大会, 電気学会, 東京
06 Sep. 2017

Spatial distributions of lightning electrical properties over estern part of Japan by ELF and LLP observations
Y. Hobara; J. Yamashita; R. Murai; T. Narita; H. Mitsuzuka
Oral presentation, English, URSI 2017 GASS, Montreal, International conference
23 Aug. 2017

Multi step ahead prediction of nighttime VLF amplitude signal for low-mid and high-latitude paths
H. Santosa; Y. Hobara
Oral presentation, English, URSI 2017 GASS, Montreal,Canada, International conference
23 Aug. 2017

Response of the sub-ionospheric VLF-LF signals to the major SSW event of 2009
S. Pal; Y. Hobara; S. K. Chakrabarti; P. W. Schnoor
Poster presentation, English, URSI 2017 GASS, Montreal,Canada, International conference
23 Aug. 2017

Recent results from the Japanese total lightning network, Japan Geoscience Union Meeting 2017
S. Kono; Y. Hobara; S.Heckman; C.Liu
Oral presentation, English, Japan Geoscience Union Meeting 2017, Makuhari,Chiba
22 May 2017

Ionospheric perturbations due to earthquakes observed simultaneously by subionospheric VLF/LF wave and GPS TEC measurements
H. Santosa; Y. Hobara; T. Tsuda; S. Srinivas
Oral presentation, English, Japan Geoscience Union Meeting 2017, Makuhari,Chiba
22 May 2017

Statistical, study of maximum ionospheric electron density deduced from lightning whistlers obtained by DEMETER
G.Yiddidya; Y. Hobara; P. Michel
Poster presentation, English, Japan Geoscience Union Meeting 2017, Makuhari,Chiba
22 May 2017

Improving accuracy of locations and lightning charge moment changes using multi-point simultaneous obsevations of ELF transients
R. Murai; Y. Hobara; J. Yamashita; S. Heckman
Oral presentation, English, Japan Geoscience Union Meeting 2017, Makuhari,Chiba
22 May 2017

Accuracy Verification of Lightning Charge Moment Change Remotely Estimated by ELF Observations using Direct Lightning Charge Masurements at Wind Turbine
Y. Hobara; J. Yamashita; Y. Matsui; S. Murai; T. Narita; H. Mitsuzuka
Oral presentation, English, ISWL2017, Joetsu, Niigata, Japan, International conference
12 Apr. 2017

Preliminary Results from total lightning observation in Japan
Y. Hobara
Oral presentation, English, The Atmospheric Global Electric Circuit (GEC), International conference
Feb. 2017

非線形システム同定手法を用いた下部電離層状態の予測および擾乱原因の解明に関する研究
松井優磨; H. Santosa; M. Balikhin; 芳原容英
Oral presentation, Japanese, 第95回日本大気電気学会
06 Jan. 2017

The vertical coupling of Tsunami induced ionospheric perturbations from subionospheric VLF/LF waves and GPS TEC measurements for Tohoku earthquake
H.Santosa; S. Srinivas; T. Tsuda; Y. Hobara
Oral presentation, Japanese, 第95回日本大気電気学会
06 Jan. 2017

国際宇宙ステーションGLIMS ミッションにより観測された雷発光強度を用いた雷の電気的特性導出に関する研究
鈴木克徳; 柿沼遠方; 芳原容英; 佐藤光輝; 高橋幸弘; 足立透; 牛尾知雄; 河崎善一郎; 森本健志; 山崎敦; 鈴木睦; I.R.Linscott; U.S. Inan
Oral presentation, Japanese, 第95回日本大気電気学会
06 Jan. 2017

対流圏の雷活動と高高度電離圏の応答に関する研究
竹本未来; 芳原容英; Jean-Louis Pincon; Michel Parrot
Oral presentation, Japanese, 第95回日本大気電気学会
06 Jan. 2017

非線形信号処理手法を用いたULF 帯磁場変動のモデリングに関する研究
飯淵隼人; 芳原容英; 松井優磨
Oral presentation, Japanese, 第95回日本大気電気学会
06 Jan. 2017

激しい降水事象に伴うトータル雷の時空間変動に関する研究
小川哲也; 甲野慎太郎; 岩崎博之; 清水慎吾; 芳原容英
Oral presentation, Japanese, 第95回日本大気電気学会
06 Jan. 2017

Multi-step Ahead Prediction of Midlatitude Daily Nighttime Subionospheric VLF Signals using NARX NN Modeling
H. Santosa; Y. Hobara; Y. Matsui
Oral presentation, English, The Irago Conference
01 Nov. 2016

Reliability of Dual and Triple Frequency Ionosphere-free Linear Combination of GPS for Single Point Positioning
V. Satya Srinivas; Y. Hobara
Oral presentation, English, The Irago Conference
01 Nov. 2016

Prediction of Nighttime VLF Signal Amplitude for Mid-and High-Latitude Paths
H. Santosa; Y. Hobara
Oral presentation, English, Japan Geoscience Union Meeting 2016, Makuhari,Chiba
25 May 2016

Statistical study on the Relationship between Major Earthquakes and Lower Ionospheric Perturbations based on the Focal Mechanism and Nighttime Fluctuation Method
T. Kawano; K.Tatsuta; Y. Hobara
Oral presentation, English, Japan Geoscience Union Meeting 2016, Makuhari,Chiba
25 May 2016

Ionospheric perturbations due to earthquakes observed simultaneously by subionospheric VLF/LF wave and GPS TEC measurements
H. Santosa; Y. Hobara; T. Tsuda; S. Srinivas
Oral presentation, English, Japan Geoscience Union Meeting 2017, Makuhari,Chiba
22 May 2016

日本トータル雷ネットワークを用いた極端気象の初期解析結果
芳原容英
Oral presentation, Japanese, 日本気象学会2016年度春季大会, 日本気象学会, 東京
21 May 2016

Tatistical study of seismo-ionospheric perturbations around Japan by using VLF/LF transmitters with a focal mechanism
T. Kawano; Y. Hobara; K. Tatsuta
Oral presentation, English, European Geosciences Union General Assembly 2016, Vienna,Austria, International conference
20 Apr. 2016

Electrical properties of lightning over northern part of Japan by using ELF and LLP observations
Y. Hobara; J. Yamashita; T. Narita; H. Mitsuzuka
Oral presentation, English, European Geosciences Union General Assembly 2016, Vienna,Austria, International conference
20 Apr. 2016

tatistical study of seismo-ionospheric perturbations around Japan by using VLF/LF transmitters with a focal mechanism
T.Kawano; Y.Hobara; K.Tatsuta
Oral presentation, English, European Geosciences Union General Assembly 2016, Vienna,Austria, International conference
20 Apr. 2016

ELF帯電波観測を用いた関東周辺の落雷に伴う電荷モーメントの推定と地域特性及び季節変化に関する研究
山下純平; 芳原容英; 成田知巳; 三塚洋明
Oral presentation, Japanese, 平成２８年 電気学会全国大会
16 Mar. 2016

極超長波(ELF)を用いた落雷電荷量の推定精度検証
成田知巳; 三塚洋明; 太田浩; 山下純平; 芳原容英; 三木貫; 齋藤幹久
Oral presentation, Japanese, 平成２８年 電気学会全国大会
16 Mar. 2016

ミッションにより観測された雷放電の発光面積・強度とその電気的特性に関する研究
柿沼遠方; 芳原容英; 牛尾知雄; 河崎善一郎; 森本健志; 佐藤光輝; 山崎敦; 鈴木睦
Oral presentation, Japanese, 日本大気電気学会 第94回, Domestic conference
09 Jan. 2016

発震機構及び電波観測を用いた地震-電離層擾乱関連性の評価
河野友紀; 龍田健心; 芳原容英
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

台湾における、VLF送信電波を用いた地震に関連する電離層擾乱の調査
小泉雅大; 龍田健心; 河野友紀; 芳原容英; C; H. Chen
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

ELF帯及び広帯域雷観測網を併用した雷放電に伴う電荷モーメントの空間分布の初期解析結 果
石井遵平; 山下純平; 芳原容英
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

電通大トータル雷観測データを用いた国内突風現象に先行するライトニングジャンプに関する研究
熊谷悠里; 石井颯杜; 芳原容英; S. Heckman; C. Liu
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

ELF帯電波及び LLS観測による関東周辺の落雷に伴う電荷モーメントの推定と地域特性に関する研究
山下純平; 芳原容英; 成田知巳; 三塚洋明
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

The NARX Neural Network Model for Predicting Daily Nighttime VLF Amplitude NPM-CHF Path
H. Santosa; Y. Hobara
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

日本国にて発生した竜巻に伴うトータル雷と降水特性に関する調査
甲野慎太郎; 石井颯杜; 熊谷悠里; 芳原容英; C. Liu; S. Heckman
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

竜巻をもたらすメソサイクロンとトータル雷に関する研究
石井颯杜; 芳原容英; C. Price; E. Williams
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

DEMETER 衛星による雷起源ホイスラを用いた世界電子密度推定に関する研究
Yididya Girma; 鈴木克徳; 芳原容英; M. Parrot; J-L. Pincon
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

ロングリカバリーアーリーVLF 電波擾乱を引き起こす雷特性に関する研究
山田大開; 山下純平; 芳原容英
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

雷嵐に対する下部電離層応答に関する統計的研究
小川尚志; 河野友紀; 松井優磨; 芳原容英
Oral presentation, Japanese, 日本大気電気学会第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

非線形同定手法を用いた下部電離層状態のモデリング及び予測に関する研究
松井優磨; 龍田健心; H. Santos; M. Balikhin; 芳原容英
Oral presentation, Japanese, 日本大気電気学会 第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

Modeling of lower ionosphere and using the wave propagation theory, the computation of diurnal variations of multi-transmitter VLF signals at Antarctic station
T. Basak; Y. Hobara
Oral presentation, Japanese, 日本大気電気学会第94回, 日本大気電気学会, 東京, Domestic conference
09 Jan. 2016

Determination of Spatio-Temporal Characteristics of D-region Electron Density during Annular Solar Eclipse from VLF Network Observations
T. Basak; Y. Hobara
Oral presentation, English, American Geophysical Union Fall Meeting, International conference
15 Dec. 2015

Prediction of the Nighttime VLF Subionospheric Signal Amplitude by Using Nonlinear Autoregressive with Exogenous Input Neural Network
H. Santosa; Y. Hobara; M. Balikhin
Oral presentation, English, American Geophysical Union Fall Meeting, International conference
15 Dec. 2015

Preliminary Results form the Japanese Total Lightning Network
Y. Hobara; H. Ishii; Y. Kumagai; C. Liu; S. Heckman; C. Price; E. R. Williams
Oral presentation, English, American Geophysical Union Fall Meeting, International conference
15 Dec. 2015

Prediction of the Nighttime VLF Subionospheric Signal Amplitude by Using Nonlinear Autoregressive with Exogenous Input Neural Network Model
H. Santosa; Y. Hobara; M. Balikhin
Oral presentation, English, American Geophysical Union Fall Meeting, International conference
15 Dec. 2015

A Statistical Study on VLF Subionospheric Perturbations Associated with Major Earthquakes: A View from Focal Mechanism
T. Kawano; K. Tatsuta; Y. Hobara
Poster presentation, English, American Geophysical Union Fall Meeting, American Geophysical Union, San Francisco, International conference
15 Dec. 2015

Atmosphere and Ionosphere Connection as Revealed by the Network Observation of Very Low Frequency Radio Signals
S. Pal; Y. Hobara
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

A Statistical Study of Sub-ionospheric VLF Signal Anomaly Due to Geomagnetic Storms
K. Tatsuta; Y. Hobara
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

Statistical Spatial Distributions of Lightning with Charge Moment Changes Over Northern Area of Japan by ELF and LLS Observations
J. Yamashita; Y. Hobara
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

Modeling and Possible Determination of D-region Ionospheric Perturbation during Annular Solar Eclipse on May 21, 2012, From VLF Signal Simulation and Multi-Propagation Path Observation From UEC-VLF Network: Preliminary Results
T. Basak; Y. Hobara
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

A Novel Prediction for Very Low Frequency Transmitter Signal Amplitude Using NARX Neural Network
H. Santosa; Y. Hobara
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

Electron Density Estimation by Using Simultaneous Observations of Lightning Optical Emissions and Whistlers from ISS GLIMS Mission
K. Suzuki; Y. Hobara; K. Kakinuma
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

VHF Lightning Observations and DOA Estimation From ISS /JEM-GLIMS
T. Morimoto; H. Kikuchi; T. Ushio; M. Sato; A. Yamazak; M.Suzuki; Y. Hobara
Oral presentation, English, 2015 URSI-Japan Radio Science Meeting, Tokyo
04 Sep. 2015

Spatial Distributions of Lightning with Charge Moment Change over northern Part of Japan by ELF and LLP Observations
Y. Hobara; J. Yamashita; T. Narita
Oral presentation, English, Asia-Pacific International Conference 2015, Nagoya,Japan, Domestic conference
25 Jun. 2015

地震先行下部電離層擾乱と地震の発震機構との関係
河野友紀; 龍田健心; 芳原容英
Oral presentation, Japanese, JpGU2015, 日本地球惑星科学連合, 幕張、千葉, Domestic conference
26 May 2015

国際宇宙ステーションGLIMSミッションにより観測された雷発光とホイスラを用いた電離層Ｆ層の電子密度推定
鈴木克徳; 柿沼遠方; 芳原容英; L. Ivan; I. Umran; 佐藤光輝; 高橋幸弘; 牛尾知雄; 河崎善一郎; 森本健志; 山崎敦; 鈴木睦
Oral presentation, Japanese, JpGU2015, 日本地球惑星科学連合, 幕張、千葉
25 May 2015

国内初トータルライトニングネットワークによる突風現象による雷活動の初期観測結果
熊谷悠里; 石井颯杜; 芳原容英; S. Heckman; C. Liu
Oral presentation, Japanese, JpGU2015, 日本地球惑星科学連合, 幕張、千葉, Domestic conference
25 May 2015

Relationship between the nighttime VLF amplitude and total column ozone density:possibility of monitoring atmospheric ozone from VLF remote sensing
S. Pal; Y. Hobara
Invited oral presentation, English, 1st URSI Atlantice Radio Science Conferece (URSI AT-RASC), Invited, Spain, International conference
19 May 2015

Estimating ionospheric property by using simultaneous observations of lightning optical emissions and whistlers from ISS GLIMS mission.
K. Suzuki; Y. Hobara; K. Kakinuma; M. Sato; Y. Takahashi; T. Ushio; T. Morimoto; A. Yamazaki; M. Suzuki; Linscott IR; Inan US
Poster presentation, English, European Geosciences Union General Assembly 2015, Vienna,Austria, International conference
16 Apr. 2015

Severe weather detection by using Japanese Total Lightning Network
Y. Hobara; H. Ishii; Y. Kumagai; C. Liu; S. Heckman; C. Price
Oral presentation, English, European Geosciences Union General Assembly 2015, Vienna,Austria, International conference
16 Apr. 2015

関東周辺での落雷に伴う電荷モーメントの地域特性に関する研究
山下純平; 芳原容英; 成田知巳
Oral presentation, Japanese, 平成２７年度電気学会全国大会
26 Mar. 2015

極超長波を用いた雷撃電荷量推定に関する検討
成田知巳; 山口 寛; 太田 浩; 山下純平; 芳原容英
Oral presentation, Japanese, 平成２７年度電気学会全国大会
26 Mar. 2015

VLF/LF帯送信局電波の振幅及び位相情報を用いた地震に伴う下部電離層擾乱の位置・空間スケール同定に関する研究
龍田健心; 芳原容英; T. Basak
Oral presentation, Japanese, 日本大気電気学会 第92回, 千葉大学, Domestic conference
09 Jan. 2015

地震の発震機構と先行する下部電離層擾乱との関係
河野友紀; 龍田健心; 芳原容英
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

日本国内トータルライトニングの夏期初期観測結果と局所的気象災害との関係性
熊谷悠里; 石井颯杜; 芳原容英; S. Heckman; C. Liu
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

極端気象に伴う雷放電及び降水領域の移動に関する研究
石井颯杜; 芳原容英; C. Price
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

国際宇宙ステーションGLIMSミッションにより観測されたホイスラを用いた電離層F層の電子密度推定
鈴木克徳; 芳原容英; I. R. Linscott; U. S. Inan; 佐藤光輝; 高橋幸弘; 牛尾知雄; 河崎善一郎; 森本健志; 山崎敦; 鈴木睦
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

大規模気象擾乱に伴う大気圏電離圏結合に関する研究
松井優磨; 芳原 容英
Oral presentation, Japanese, 日本大気電気学会 第92回, 千葉大学, Domestic conference
09 Jan. 2015

VLF送信電波ネットワーク観測を用いた金環日食に伴う下部電離層擾乱領域の同定に関する研究
乾大輝; 芳原容英; S. Pal
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

人工衛星観測による全球にわたる雷起源の電磁波特性に関する研究
阿部利之; 芳原容英; M.Parrot
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

JEM-GLIMSミッションにより観測された雷発光現象と落雷電荷モーメントとの関係
柿沼遠方; 芳原容英; 牛尾知雄; 河崎善一郎; 森本健志; 佐藤光輝; 山崎敦; 鈴木睦
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

関東周辺での落雷に伴う電荷モーメントの地域特性に関する研究
山下純平; 芳原容英; 成田知己
Oral presentation, Japanese, 日本大気電気学会 第92回, Invited, 千葉大学, Domestic conference
09 Jan. 2015

ELF帯電波観測を用いた落雷電荷モーメント分布のリアルタイム表示システムに関する研究
相川龍大; 山下純平; 芳原容英; 塩川和夫
Oral presentation, Japanese, 日本大気電気学会 第92回, Domestic conference
09 Jan. 2015

Simultaneous Observations of Ionospheric Disturbances from VLF Transmitter Signals and Surface Displacements from GPS Related to Inland Earthquakes Over Japan
Y. Hobara; R. Miyake; C. Chen
Oral presentation, English, URSI GASS, URSI GASS, BEIJING, International conference
Aug. 2014

Spatio-Temporal Characteristics of Subionospheric Perturbations Associated With Annular Solar Eclipse over Japan: Network Observations and Modeling
D. Inui; Y. Hobara
Oral presentation, English, URSI GASS, URSI GASS, BEIJING, International conference
Aug. 2014

LF帯雷標定およびアメダスデータを用いた落雷と局所的気象擾乱との関連性に関する研究
石井颯杜; 芳原容英; C. Price
Oral presentation, Japanese, 日本大気電気学会 第91回研究発表会, 群馬大学
04 Jul. 2014

地磁気変動とVLF / LF 帯送信局電波伝搬異常の関連性に関する研究
龍田健心; 芳原容英; M. A. Balikhin
Oral presentation, Japanese, 日本大気電気学会 第91回研究発表会, 群馬大学
04 Jul. 2014

Possible relation between night time VLF amplitude and total Ozone variation
S. Pal; Y. Hobara
Oral presentation, English, Society of Atmospheric Electicity of Japan
04 Jul. 2014

Simultaneous Observations of Surface Displacements from GPS and Ionospheric Perturbations from VLF Transmitter Signals Around Major Seismic
Y. Hobara; R. Miyake; C. H. Chen
Oral presentation, English, AOGS2014, AOGS, Sapporo
Jul. 2014

VLF Subionospheric Disturbances and Causative Lightning Properties by using Ground Observations and ISS GLIMS Mission
Y. Hobara; K .Kakinuyma; M. Sato; T. Ushio; T. morimot; A. Yamazaki; M. suzuki; M. kikuchi; Y. Takahashi; U. Inan
Oral presentation, English, AOGS2014, AOGS, Sapporo
Jul. 2014

Deducing Locations and Charge Moment Changes of Lightning Discharges by ELF Network Observations in Japan
Y. Hobara; T. Inoue; M. Hayakawa; K. Shiokawa
Oral presentation, English, ICAE 2014, Oklahoma, International conference
16 Jun. 2014

VLF subionospheric disturbances and electrical properties of lightning discharges observed by JEM-GLIMS mission
柿沼遠方; 芳原容英; 牛尾知雄; 佐藤光輝; 高橋幸弘; 鈴木睦
Poster presentation, Japanese, Japan Geoscience Union Meeting 2014, Domestic conference
30 Apr. 2014

金環日食に伴う下部電離層擾乱の時空間特性に関する研究
乾大輝; 芳原容英
Oral presentation, Japanese, Japan Geoscience Union Meeting 2014, Domestic conference
29 Apr. 2014

ロングリカバリーVLFイベントを発生させる雷放電の電気的特性
山下純平; 芳原容英
Oral presentation, Japanese, Japan Geoscience Union Meeting 2014, Domestic conference
29 Apr. 2014

Study on lithosphere-atmosphere-ionosphere coupling inferred from the data of GPS surface displacement and ionopheric pe
芳原容英; 三宅梨沙; C. C. Hung
Oral presentation, Japanese, Japan Geoscience Union Meeting 2014, Domestic conference
29 Apr. 2014

VLF送信電波の振幅及び位相情報を用いた地震に伴う下部電離層擾乱の位置・空間スケール同定に関する研究
龍田健心; 芳原容英
Poster presentation, Japanese, Japan Geoscience Union Meeting 2014, Domestic conference
29 Apr. 2014

Study on Lithosphere-Atmosphere-Ionosphere(LAIC)Coupling by Using Satellite-Ground-Based Measurements and Numerical Modeling
Y. Hobara
Invited oral presentation, English, 6th Isradynamics meeting, Invited, EIN BOKEK, International conference
16 Mar. 2014

電波を用いた地球環境の監視と予測
芳原容英
Public discourse, Japanese, 気象予測に関する研修会
15 Jan. 2014

人工衛星による電波観測を用いた世界雷領域別発生頻度および電気的特性に関する研究
阿部利之; 芳原容英; M. Parrot
Oral presentation, Japanese, 日本大気電気学会第90回研究発表会
Jan. 2014

地震先行ELF/ULF帯磁場異常の統計的研究
安江剛広; 芳原容英; A. Y. Schekotov
Oral presentation, Japanese, 日本大気電気学会第90回研究発表会
Jan. 2014

Simultaneous study of ULF/VLF anomalies associated with earthquakes occurred in Japan
V. Singh; Y. Hobara; M. Hayakawa
Oral presentation, English, 日本大気電気学会第90回研究発表会
Jan. 2014

南極昭和基地におけるVLF帯送信電波を用いた電離層擾乱の観測可能性に関する調査
荒舩健; 芳原容英; 岡田雅樹; 山岸久雄
Oral presentation, Japanese, 日本大気電気学会第90回研究発表会
Jan. 2014

金環日食に伴う下部電離層擾乱の時空間特性に関する研究
乾大輝; 芳原容英
Oral presentation, Japanese, 日本大気電気学会第90回研究発表会, 東京
Jan. 2014

Simultaneous Observations of Ionospheric Disturbances from VLF Transmitter Signals and Surface Displacements from GPS Related to Inland Earthquakes Over Japan
Y. Hobara; R. Miyake; C. Chen; M. Hayakawa
Invited oral presentation, English, American Geophysical Union, Fall Meeting 2013, International conference
Dec. 2013

Simultaneous study of ULF/VLF anomalies associated with earthquakes occurred in Japan
Y. Hobara; V. Singh
Invited oral presentation, English, American Geophysical Union, Fall Meeting 2013, International conference
Dec. 2013

電通大VLF帯電波観測ネットワークを用いた金環日食に伴う下部電離層擾乱の観測及び数値解析
乾大輝; 芳原容英
Oral presentation, Japanese, 日本大気電気学会第89回研究発表会
Jul. 2013

地震に先行するELF帯磁場放射とULF帯磁場減少の比較および統計的研究
安江剛; 芳原容英; A. Y. Schekotov
Oral presentation, Japanese, 日本大気電気学会第89回研究会発表会
Jul. 2013

電磁気情報の観測による地震予測
芳原容英
Public discourse, Japanese, 非常通信セミナー, Invited, 総務省中国総合通信局, 広島市, Domestic conference
27 Jun. 2013

Comparative study of ULF depression and ELF radiation associated with seismic activity
Y. Hobara; T. Yasue; A. Schekotov; M. Hayakawa
Oral presentation, English, Japan Geoscience Union Meeting 2013
May 2013

VLF subionospheric disturbances and ELF transients associated with TLEs: Observations and modeling
Y. Hobara; M. Hayakawa; H. Fujii; K. Ohta
Invited oral presentation, English, IWSE-AS 2010, International Workshop on Seismo-Electromagnetics and Atmospheric Science (IWSE-AS 2010), Agra, India, International conference
Nov. 2010

Ionospheric turbulence linked to energetic seismic events observed by DEMETER
Y. Hobara; M. Hayawaka; M. Parrot
Invited oral presentation, English, AP-RASC'10, Asia-Pacific Radio Science Conference, Taipei, International conference
Sep. 2010

Cluster及びThemis衛星を用いた準垂直衝撃波ランプ幅の統計的研究
Y. Hobara; M. A. Balikhin; S. Walker; V. Krasnoselskikh; M. Gedalin
Oral presentation, Japanese, 大気電気学会誌,日本大気電気学会第83回研究発表会
Jul. 2010

Characteristics of terrestrial foreshock ULF waves.
Y. Hobara; S. N. Walker; M. Balikhin; O. A. Pokhotelov; M. Dunlop; H. Nilsson; H. Rème
Invited oral presentation, English, Western Pacific Geophysics Meeting, アメリカ地球物理学会, Taipei, International conference
Jun. 2010

Characteristics of terrestrial foreshock ULF waves.
Y. Hobara; S. N. Walker; M. Balikhin; O. A. Pokhotelov; M. Dunlop; H. Nilsson; H; e
Invited oral presentation, English, Western Pacific Geophysics Meeting, アメリカ地球物理学会, Taipei, International conference
Jun. 2010

Statistical study of the ionospheric turbulence linked to energetic seismic
Y. Hobara; M. Suzuki; M. Hayakawa
Oral presentation, English, Japan Geoscience Union MEETING
May 2010

VLF subionospheric disturbances and ELF transients associated with TLEs: observations and modeling
Y. Hobara
Invited oral presentation, English, Very Low Frequency Radio Waves: Theory&Observations (VELFRATO-10), S.N. Bose National Centre For Basic Sciences (DST) Indian Space Research Organization (ISRO), Kolkata, India, International conference
Mar. 2010

Sprites over Africa during the AMMA with Multiple Electromagnetic Detections of Their Parent Lightning Flashes
Y. Hobara; E. Williams; R. Boldi; B. Russell; G. Satori; J. Bor; W. Lyons; S. Cummer; Y. Takahashi; M. Sato; C. Price; M. Hayakawa
Oral presentation, English, Japan Geoscience Union MEETING
May 2009

JEM-GLIMS Mission
T. Ushio; M. Sato; M. Suzuki; Y. Takahashi; T. Morimoto; Y. Hobara; M. Kikuchi; A. Yamazaki; T. Abe; Z. Kawasaki
Oral presentation, English, Japan Geoscience Union MEETING
May 2009

Characteristics of ELF waves in the ionosphere by simultaneous measurements of satellite and ground-based experiment
Y. Hobara; M. Hayakawa; M. Parrot
Oral presentation, English, Japan Geoscience Union MEETING
May 2009

フラクタル解析とELF帯電磁波動を用いたアフリカ大規模落雷特性に関する研究
白旗克基; 芳原容英; 早川正士; ガブリエラ・サトリ; アール・ウィリアムズ
Oral presentation, Japanese, 大気電気学会誌,日本大気電気学会第80回研究発表会
2009

Cluster observations of plasma waves in the vicinity of the terrestrial foreshock
Y. Hobara; M. Balikhin; S. Walker; O. A. Pokhotelov; M. Dunlop; H. Reme
Oral presentation, English, 大気電気学会誌,日本大気電気学会第80回研究発表会
2009

雷起源電磁波動の人工衛星、地上同時観測による電離層伝搬特性の導出
内田健斗; 芳原容英; 早川正士; 中村崇司; ミッシェル・パロ
Oral presentation, Japanese, 大気電気学会誌,日本大気電気学会第80回研究発表会
2009

ELFトランジェントの同定手法の比較検討
中村崇司; 関口美菜子; 早川正; 芳原容英
Oral presentation, Japanese, 大気電気学会誌,日本大気電気学会第80回研究発表会
2009

シューマン共振現象を用いた地球温暖化モニターに関する研究
原田匠; 芳原容英; 関口美菜子; 早川正士; 太田健次; アール・ウィリアムズ
Oral presentation, Japanese, 大気電気学会誌,日本大気電気学会第80回研究発表会
2009

Global measurements of lightning and sprites from International Space Station: JEMGLIMS mission
M. Sato; T. Ushio; T. Morimoto; Y. Takahashi; I. Umran; Y. Hobara; M. Kikuchi; M. Suzuki; A. Yamazaki; T. Abe; K. Yoshida; Y. Sakamoto; K. Okuyama; R. Ishida; Z. Kawasaki
Oral presentation, English, Japan Geoscience Union MEETING
2009

Current Status of the Lightning and Sprite Measurements from International Space Station
T. Ushio; M. Sato; M. Suzuki; Y. Takahashi; T. Morimoto; Y. Hobara; M. Kikuchi; A. Yamazaki; T. Abe; Z. Kawasaki
Oral presentation, English, Japan Geoscience Union MEETING
2009

３大学協働基礎ゼミ
The University of Electro-Communications

３大学協働基礎ゼミ
電気通信大学

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

大学院電磁波環境観測技術特論
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

基礎演習Ａ
The University of Electro-Communications

基礎演習Ａ
電気通信大学

波動と光
The University of Electro-Communications

波動と光
The University of Electro-Communications

波動と光
電気通信大学

物理学概論第二
The University of Electro-Communications

大学院技術英語
The University of Electro-Communications

情報・通信演習2
The University of Electro-Communications

大学院電磁波環境観測技術特論
The University of Electro-Communications

大学院電磁波環境観測技術特論
電気通信大学

大学院総合コミュニケーション科学
The University of Electro-Communications

大学院総合コミュニケーション科学
電気通信大学

情報・通信演習2
The University of Electro-Communications

情報・通信演習2
電気通信大学

物理学概論第二
The University of Electro-Communications

物理学概論第二
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

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

日本地震予知学会

SGEPSS

日本地球惑星科学連合

電気学会

日本大気電気学会

URSI

American Geophysical Union

雷嵐の複合電波観測と水蒸気観測による集中豪雨の早期監視と予測
芳原 容英; 菊池 博史; 牛尾 知雄; 川口 則幸
日本学術振興会, 科学研究費助成事業, 電気通信大学, 基盤研究(B), 23H01254
01 Apr. 2023 - 31 Mar. 2026

地上電波観測による高エネルギー電子降下機構の解明と地球中層大気への影響
01 Apr. 2020 - 31 Mar. 2023

雷嵐の電波観測と高速気象レーダ観測との融合による極端気象雷災害の監視と予測
01 Apr. 2019 - 31 Mar. 2022

雷嵐の電波観測と気象観測の融合が拓く、極端気象、雷災害の監視と短期予測の研究
01 Apr. 2016 - 31 Mar. 2019

VLF電波観測による下部電離層擾乱の監視
村田学術財団, 研究者海外派遣援助
Aug. 2017

電磁気手法を用いた地球環境の監視と予測
芳原容英
Principal investigator
2012 - 2017

極域におけるＶＬＦ帯送信電波を用いた下部電離層擾乱に関する研究
芳原容英
Principal investigator
2013 - 2016

電磁波及び光学総合観測による冬季雷特性の解明
芳原 容英
日本学術振興会, 科学研究費助成事業, 電気通信大学, 奨励研究(A), 11750229
1999 - 1999

Cloud-to-Ionosphere Discharge, Electromagnetic Radiation and Their Effect on Power Transmission.
HAYAKAWA Masashi; OHTA Kenji; HOBARA Yasuhide
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (B), It is well known that winter lightning in the Japan sea area has a significant characteristic of positive cloud-to-ground discharge (+CG), and that it has an extremely serious influence on the power transmission in the area of Hokuriku. Such +CG is recently found to trigger a strong electric field in the atmosphere, inducing red sprites (or so) and leading to the perturbation in the lower ionosphere. This work will focus on the complete understanding of this upper atmosphere discharges and the associated phenomena, and also on the effect of such discharges on the power transmission. During the winter of 1997/1998, we tried the first experiment for the Hokuriku winter lightning and the associated phenomena ; (1) optical measurement from Mt. Zao in Tahara town near Toyohashi, (2) observation of ELF transients from the upper atmosphere discharges at Moshiri in Hokkaido, and (3) VLF scattering from the lower ionospheric perturbations (by means of the NWC subionospheric signal propagation). In the first winter the optical measurement was not so good due to the insufficient preparation, but we can list the important features for other phenomena. When we compare the associated phenomena (ELF sferics and VLF scattering) for +GG and -CG, it is found that +CG could trigger ELF transients and ionospheric perturbation more often (by about twice) than for -CG.However, this difference is not so big when we assume the presence of plasma column below the lower ionosphere, which means that this kind of hypothesis of such a plasma column is questionable. During the next winter of 1998/1999, we made the successful measurement again, and we are now analyzing the data extensively. We do hope that we could obtain significant results, especially with great emphasis on the optical measurement. Finally, the coupling of such discharges on the power transmission (or transmission lines) was investigated. Then, we have obtained the voltage and current induced at the end of the transmission line by means of the transmission line model., 09450110
1997 - 1998

Role of ULF emissions in the terrestrial electromagnetic environment
HAYAKAWA Masashi; HOBARA Yasuhide; SHIMAKURA Shin; OHTA Kenji
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for international Scientific Research, Result activities have shown that the electromagnetic phenomena are becoming a very promising candidate for the short-term earthquake prediction. Among the seismo-radio emissions in a different frequency range (from DC to HF), the most promising is the ULF emission, though its history is not sufficient. In this research, we would like to accumulate the convincing data on seismo ULF emissions as many as possible, and then by using those data we will elucidate the mechanism of their generation and propagation. This research has indicated the following important findings as listed below. (1) Russian ULF sensors (torsion-type magnetometer) works very well in IZU (and Chiba) area ; especially, their sensitivity is good enough, and the data are being accumulated regularly. (2) Differential array in IZU (composed of 3 or 4 sensors) is very effective for seismo-ULF emissions, such that it increases the S/N ratio for seismo-ULF waves by 30-40dB. (3) The polarization ratio (Z/H Z vertical and H horizontal component of ULF magnetic field) is again confirmed to be effective in distinguishing seismo-ULF emission from other noises (geomagnetic pulsations). (4) ULF data for other earthquakes (Biak, Guam etc.) were analyzed. and we paid great attention to the fractal analysis. It is found that this kind of fractal analysis would be useful to investigate the large-scale characteristics of the focal zone., 09044067
1997 - 1998

函館工業高等専門学校専攻科 システム工学専攻の学生１名をインターンシップで研究室に受入れ、研究指導を行った。
2017 - 2017