柳澤 正久
| 名誉教授・その他関係者 | 名誉教授 |
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論文
- Radiative characteristics of the Chelyabinsk superbolide
Masahisa Yanagisawa
PLANETARY AND SPACE SCIENCE, PERGAMON-ELSEVIER SCIENCE LTD, 118巻, 掲載ページ 79-89, 出版日 2015年12月, 査読付, On Feb. 15, 2013, a meteoroid with a size of about 19 m plunged into the terrestrial atmosphere at 19 km s(-1) and burst at an altitude of about 30 km over the city of Chelyabinsk, Russia. Here we present light curves for the bolide in the red, green, and blue color bands, derived from an analysis of a video that was recorded by a dashboard camera and released on the Internet. Our results demonstrate that the bolide was blue-green in color, which is inconsistent with the Planck spectrum before the meteoroid began to fragment. Fragmentation triggered a flare-up of the bolide and 90% of its radiation energy at optical wavelengths was released within a period of about 2 s after that. During the same period, the brightness ratios among the three bands became consistent with 4000 K blackbody radiation. Based on the peak luminosity, a surface area of several square kilometers would be required for a 4000 K blackbody. It is considered that the radiation source of the bolide was an elongated cloud of vapor and debris produced through severe fragmentation of the meteoroid. (C) 2015 Elsevier Ltd. All rights reserved.
研究論文（学術雑誌）, 英語 - Ultra-high-speed photography and optical flash measurements of Nylon sphere impact phenomena
M. Yanagisawa; K. Kurosawa; S. Hasegawa
The 13th Hypervelocity Impact Symposium, Elsevier, 13巻, 出版日 2015年, 査読付
研究論文（国際会議プロシーディングス）, 英語 - Ultra-High-Speed Photography and Optical Flash Measurement of Nylon Sphere Impact Phenomena
M. Yanagisawa; K. Kurosawa; S. Hasegawa
Procedia Engineering, Elsevier, 103巻, 掲載ページ 657-662, 出版日 2015年, 査読付
研究論文（学術雑誌）, 英語 - Lightcurves of the Chelyabinsk bolide derived from a dashboard camera movie
Masahisa Yanagisawa
Asteroids, Comets, Meteors Book of Abstracts, Asteroids, Comets, Meteors, 1巻, 掲載ページ 613-613, 出版日 2014年06月, 査読付
研究論文（国際会議プロシーディングス）, 英語 - チェリャビンスク火球の明るさと色の時間変化：Web動画の解析から
柳澤正久
日本惑星科学会誌「遊星人」, 日本惑星科学会, 23巻, 2号, 掲載ページ 82-91, 出版日 2014年06月, 査読付, 招待
研究論文（学術雑誌）, 日本語 - SuprimeCam observation of sporadic meteors during Perseids 2004
Masanori Iye; Mikito Tanaka; Masahisa Yanagisawa; Noboru Ebizuka; Kouji Ohnishi; Chikako Hirose; Naoko Asami; Yutaka Komiyama; Hisanori Furusawa
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, OXFORD UNIV PRESS, 59巻, 4号, 掲載ページ 841-855, 出版日 2007年08月, 査読付, We report on serendipitous findings of 13 faint meteors and 44 artificial space objects by SuprimeCam imaging observations during 2004 August 11-16. The meteors, at about 100 km altitude, and artificial satellites/debris in orbit, at 500 km altitude or higher, were clearly discriminated by their apparent defocused image sizes. We defined a peak video-rate magnitude by comparing the integrated photon counts from the brightest portion of the track traversed within 33 ms to those from a 0-mag star during the same time duration. The magnitudes thus defined for the meteors, including 1 Perseid, 1 Aquarid, and 11 sporadic meteors, were in the range 4.0 < V-vr < 6.4 and 4.1 < I-vr < 5.9. Although the spatial resolution is insufficient to resolve the source size of anything smaller than about I m, we developed a new estimate of the collisionally excited column diameter of these meteors. A diameter as small as a few mm was derived from their collisionally excited [0 1] 5577 photon rates, meteor speed, and the volume density of the oxygen atoms at an altitude of 100 km. The actual column diameter of the radiating zone, however, could be as large as few 100 m because the excited oxygen atoms travel that distance before they emit forbidden lines in 0.7 s of its average lifetime.
研究論文（学術雑誌）, 英語 - The first confirmed Perseid lunar impact flash
M Yanagisawa; K Ohnishi; Y Takamura; H Masuda; Y Sakai; M Ida; M Adachi; M Ishida
ICARUS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 182巻, 2号, 掲載ページ 489-495, 出版日 2006年06月, 査読付, The first confirmed lunar impact flash due to a non-Leonid meteoroid is reported. The observed Perseid meteoroid impact Occurred at 18(h)28(m)27(s) on August 11, 2004 (UT). The sclenographic coordinates of the lunar impact flash are 48 +/- 1 degrees N and 72 +/- 2 degrees E, and the flash had a visual magnitude of ca. 9.5 with duration of about 1/30 s. The mass of the impactor is estimated to have been 12, based on a nominal model with conversion efficiency from Kinetic to optical energy of 2 x 10(-3). Extrapolation of a power law size-frequency distribution fitting the sub-centimeter Perseid meteoric particles to large meteoroids suggests that several flashes should have been observed at this optical efficiency. The detection of only one flash may indicate that the optical efficiency for Perseid lunar impact is much lower, or that the slope of the size distribution differs between large meteoroids and typical sub-centimeter meteoric particles. (c) 2006 Elsevier Inc. All rights reserved.
研究論文（学術雑誌）, 英語 - Collisional spin up of nonspherical asteroids
M Yanagisawa
ICARUS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 159巻, 2号, 掲載ページ 300-305, 出版日 2002年10月, 査読付, We investigate the spin up of nonspherical asteroids by successive random collisions with other smaller asteroids. The spin-up rates are calculated for ellipsoidal and spherical bodies of the same mass. Then, we derive the relative spin-up efficiency, that is, the ratio of the spin-up rate of the ellipsoidal body to that of the spherical body. We suppose a collisional process in our model different from that adopted in the previous works. The results show that ellipsoidal bodies can spin up more rapidly than spherical bodies. (C) 2002 Elsevier Science (USA).
研究論文（学術雑誌）, 英語 - Lightcurves of 1999 Leonid impact flashes on the Moon
M Yanagisawa; N Kisaichi
ICARUS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 159巻, 1号, 掲載ページ 31-38, 出版日 2002年09月, 査読付, Optical flashes observed on the night side of the Moon during the 1999 Leonid meteor shower have attracted the interest of astronomers. These flashes are attributed to high-velocity impacts of Leonid meteoroids on the lunar surface. Here, we report five lunar flashes detected over a 5.8-h observation period centered at 11:25 UT on Nov. 18, 1999, in Japan. The flashes are characterized by an abrupt brightening. Three flashes exhibited afterglows that remained visible for at least 50 ms, which is longer than the duration predicted for radiation from an impact-generated plasma cloud. We show that thermal radiation from hot droplets ejected from the lunar surface during high-velocity impacts could be the cause of the afterglows. (C) 2002 Elsevier Science (USA).
研究論文（学術雑誌）, 英語 - Leonid impact flashes on the Moon
Yanagisawa, M; N. Kisaichi
Proc. 34th ISAS Lunar Planet. Sym., 掲載ページ 126-129, 出版日 2001年
研究論文（学術雑誌）, 英語 - 獅子座流星体の月面衝突による発光
柳澤正久; 私市成美; 農澤健太郎
日本天文学会，群馬県総合教育センター，(伊勢崎), 出版日 2000年10月
日本語 - 小惑星（201）Penelopeの形状
林 悟; 柳澤正久; 長谷川均; 佐藤 勲; 中島 崇; 福島英雄
日本天文学会，群馬県総合教育センター，(伊勢崎), 出版日 2000年10月
日本語 - すばる望遠鏡による小惑星の衛星捜し
柳澤正久; 林 悟; 佐藤 勲; 長谷川直
日本天文学会，群馬県総合教育センター, 出版日 2000年10月
日本語 - 小惑星（201）Peneropeの形状
林 悟; 柳澤正久; 佐藤 勲; 長谷川均; 中島 崇; 福島英雄
惑星科学会（筑波）, 出版日 2000年10月
日本語 - 獅子座流星体の月面衝突による発光
柳澤正久; 私市成実; 農澤健太郎
惑星科学会（筑波）, 出版日 2000年10月
日本語 - Momentum transfer in oblique impacts: Implications for asteroid rotations
M Yanagisawa; S Hasegawa
ICARUS, ACADEMIC PRESS INC, 146巻, 1号, 掲載ページ 270-288, 出版日 2000年07月, 査読付, We calculate the momentum transfer efficiency for small cratering impacts from 59 high-velocity (0.76-4.4 km/s) oblique impact experiments using nylon projectiles and targets made of basalt, aluminum, mild steel, mortar, and nylon. High-speed video frames show an initial luminous stream downrange of impact point for all the target materials. For basaltic and mortar targets there follows axi-symmetric ejection of target material around surface normal at the impact point. Our results suggest that: (1) momentum carried away by the axi-symmetric ejecta would significantly contribute to the normal component of momentum transfer efficiency; and (2) the penetration depth of the projectile into target could determine the tangential momentum transfer efficiency. We calculated the efficiency of angular momentum transfer from the translational motion of projectiles to the rotation of ellipsoidal asteroids using the efficiencies for the linear momentum. The efficiency is more than four times that for spherical asteroid at their principal axis ratio of 2 : 1,4. 1 : If the experimental results hold for the impact that formed the largest crater on 253 Mathilde, the largest projectile estimated may have despun the asteroid to the present slow rotation by chance. (C) 2000 Academic Press.
研究論文（学術雑誌）, 英語 - 電気通信大学の掩蔽観測システム
柳澤正久; 林悟; 私市成実; 農澤健太郎
第16回小惑星会議（代々木オリンピックセンター）, 出版日 2000年06月
日本語 - クレーターを作ろう
高田淑子; 須田敏典; 西川洋平; 小島志穂; 小山裕幸; 佐藤一行; 豊川秀樹; 柳澤正久; 林 悟; 私市成実; 農澤健太郎
天文学会・天文教育フォーラム（東大）, 出版日 2000年04月
日本語 - The occultation of HIP047706 by（201）Penelope
Sato, I; M. Yanagisawa; S. Hayashi
Proc. 33th ISAS Lunar Planet. Sym., 掲載ページ 13-16, 出版日 2000年
研究論文（学術雑誌）, 英語 - Angular momentum transfer in oblique impacts: Implications for 1989ML
M Yanagisawa; S Hasegawa
EARTH PLANETS AND SPACE, TERRA SCIENTIFIC PUBL CO, 51巻, 11号, 掲載ページ 1163-1171, 出版日 1999年, 査読付, We conducted 10 shots of high-velocity oblique impact experiments (1.95-3.52 km/s) using nylon projectiles and spherical mortar targets. Large craters were formed, but these targets were not disrupted by the impacts. We then calculated the efficiencies of momentum transfer from the projectile to the post-impact target for each experiment. The efficiencies of angular momentum transfer from the translational motion of the projectiles to the rotation of the post-impact targets were also derived. A representative efficiency of angular momentum transfer was calculated to be 0.17 for random successive collisions. The efficiency was applied to an equation expressing the precession angle of asteroids. It is shown that 1989ML, target of Japan-US asteroid-sample-return-mission (MUSES-C) would be tumbling.
研究論文（学術雑誌）, 英語 - 斜め衝突現象
柳澤正久
地球惑星科学関連学会合同大会, 出版日 1998年06月
日本語 - レールガン実験成果報告
柳澤正久
出版日 1998年
研究論文（大学，研究機関等紀要）, 日本語 - 斜め衝突における運動量,角運動量の輸送:小惑星の自転に関連して
M Yanagisawa; S Hasegawa; N Shirogane
イカルス, ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS, 123巻, 1号, 掲載ページ 192-206, 出版日 1996年09月, 査読付, We conducted a series of high velocity oblique impact experiments (0.66-6.7 km/s) using polycarbonate (plastic) projectiles and targets made of mortar, aluminum alloy, and mild steel. We then calculated the efficiencies of momentum transfer for small cratering impacts. They are eta = (M'V'(n))/(mv(n)) and zeta = (M'V'(t))/(mv(t)), where m and v are the mass and velocity of a projectile, and M' and V' represent those of a postimpact target. Subscripts ''n'' and ''t'' denote the components normal and tangential to the target surface at the impact point, respectively. The main findings are: (1) eta increases with increasing impact velocity; (2) eta is larger for mortar than for ductile metallic targets; (3) zeta for mortar targets seems to increase with the impact velocity in the velocity range less than about 2 km/ s and decrease with it in the higher velocity range; (4) zeta for the aluminum alloy targets correlates negatively with incident zenith angle of the projectile. In addition to these findings on the momentum transfer, we show theoretically that ''zeta(L)'' can be expressed by eta and zeta for small cratering impact. Here, zeta(L) is the spin angular momentum that the target acquires at impact divided by the collisional angular momentum due to the projectile. This is an important parameter to study the collisional evolution of asteroid rotation. For a spherical target, SL is shown to be well approximated by zeta. (C) 1996 Academic Press, Inc.
研究論文（学術雑誌）, 英語 - Impact fragmentation experiments of porous and weak targets
63巻, 掲載ページ 243, 出版日 1994年, 査読付
研究論文（国際会議プロシーディングス）, 英語 - Upper limits of Europa brightening at K-nucleus impact
Earth, Moon and Planets, 66巻, 1号, 掲載ページ 129, 出版日 1994年, 査読付
研究論文（学術雑誌）, 英語 - Angular momentum transfer in low velocity oblique impacts : Implications for asteroids
ICARUS, 掲載ページ 94, 出版日 1991年, 査読付
研究論文（学術雑誌）, 英語 - Development of railgun accelerator at ISAS
IEEE Transactions on Magnetics, 掲載ページ 25, 出版日 1989年, 査読付
研究論文（学術雑誌）, 英語 - 惑星科学実験用レールガンの開発
宇宙科学研究所報告, 掲載ページ 51, 出版日 1987年, 査読付
研究論文（大学，研究機関等紀要）, 英語 - Mean Ionospheric Field Correction for MAGSAT data
Journal of Geophysical Research, 掲載ページ 90, 出版日 1985年, 査読付
研究論文（学術雑誌）, 英語 - Vacuum environment around Spacelab-1
ISAS Report, 掲載ページ 617, 出版日 1985年, 査読付
研究論文（大学，研究機関等紀要）, 英語 - Magnetic anomaly maps obtained by means of Mean Ionospheric Field Correction
Journal of Geomagnetism and Geoelectricity, 掲載ページ 36, 出版日 1984年, 査読付
研究論文（学術雑誌）, 英語 - 40Ar- 39Ar ages of boulders drilled at site 439, DSDP Leg 57
Deep Sea Drilling Project, Initial Report, 掲載ページ DSDP56-57, 出版日 1980年, 査読付
研究論文（学術雑誌）, 英語
MISC
講演・口頭発表等
担当経験のある科目_授業
- Astronomical and Earth Sciences
The University of Electro-Communications - 基礎物理学実験
The University of Electro-Communications - 基礎物理学実験
電気通信大学 - 宇宙・地球科学
The University of Electro-Communications - 宇宙・地球科学
電気通信大学 - 力学
The University of Electro-Communications - 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 - 人間と環境A1
東京外国語大学 - 人間と環境A1
東京外国語大学 - 電磁波環境観測技術特論
The University of Electro-Communications - 電磁波環境観測技術特論
電気通信大学 - 宇宙·地球科学
The University of Electro-Communications - 宇宙·地球科学
電気通信大学 - 専門基礎実験A·B
The University of Electro-Communications - 専門基礎実験A·B
電気通信大学 - Mechanics
The University of Electro-Communications - 力学
電気通信大学