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  2. 藤本 正樹

藤本 正樹

Fujimoto Masaki  (Masaki Fujimoto)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 教授 (副所長)
学位
理学博士(1992年3月 東京大学)
連絡先
fujimoto.masakijaxa.jp
J-GLOBAL ID
200901003508985603
researchmap会員ID
1000203981

2006年より、JAXA宇宙科学研究所に所属。それまでの宇宙プラズマ物理の研究に加え、太陽系探査の企画推進にも関わるように。その立場で貢献してきたものとして、JUICE, ひさき、ERG、はやぶさ２，MMX、DESTINY+。宇宙プラズマ研究において多体系の物理への興味が高かったこと、JAXAが得意とする小天体とのリンクが強いことから、N体計算からの惑星系形成論も研究テーマに追加した。また、太陽系探査以外の宇宙科学計画の国際協力調整にも携わる。

研究キーワード

 2

研究分野

 2

経歴

 3

学歴

 2

受賞

 5

論文

 171
  • Yuichiro Ezoe, Ryu Funase, Harunori Nagata, Yoshizumi Miyoshi, Hiroshi Nakajima, Ikuyuki Mitsuishi, Kumi Ishikawa, Masaki Numazawa, Yosuke Kawabata, Shintaro Nakajima, Ryota Fuse, Ralf C. Boden, Landon Kamps, Tomokage Yoneyama, Kouichi Hagino, Yosuke Matsumoto, Keisuke Hosokawa, Satoshi Kasahara, Junko Hiraga, Kazuhisa Mitsuda, Masaki Fujimoto, Munetaka Ueno, Atsushi Yamazaki, Hiroshi Hasegawa, Takefumi Mitani, Yasuhiro Kawakatsu, Takahiro Iwata, Hiroyuki Koizumi, Hironori Sahara, Yoshiaki Kanamori, Kohei Morishita, Daiki Ishi, Aoto Fukushima, Ayata Inagaki, Yoko Ueda, Hiromi Morishita, Yukine Tsuji, Runa Sekiguchi, Takatoshi Murakawa, Kazuma Yamaguchi, Rei Ishikawa, Daiki Morimoto, Yudai Yamada, Shota Hirai, Yuki Nobuhara, Yownin Albert M. Leung, Yamato Itoigawa, Ryo Onodera, Satoru Kotaki, Shotaro Nakamura, Ayumi Kiuchi, Takuya Matsumoto, Midori Hirota, Kazuto Kashiwakura
    Journal of Astronomical Telescopes, Instruments, and Systems 9(03) 2023年9月12日  
  • Toru Yada, Masanao Abe, Tatsuaki Okada, Aiko Nakato, Kasumi Yogata, Akiko Miyazaki, Kentaro Hatakeda, Kazuya Kumagai, Masahiro Nishimura, Yuya Hitomi, Hiromichi Soejima, Miwa Yoshitake, Ayako Iwamae, Shizuho Furuya, Masayuki Uesugi, Yuzuru Karouji, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Seiji Sugita, Yuichiro Cho, Koki Yumoto, Yuna Yabe, Jean-Pierre Bibring, Cedric Pilorget, Vincent Hamm, Rosario Brunetto, Lucie Riu, Lionel Lourit, Damien Loizeau, Guillaume Lequertier, Aurelie Moussi-Soffys, Shogo Tachibana, Hirotaka Sawada, Ryuji Okazaki, Yoshinori Takano, Kanako Sakamoto, Yayoi N. Miura, Hajime Yano, Trevor R. Ireland, Tetsuya Yamada, Masaki Fujimoto, Kohei Kitazato, Noriyuki Namiki, Masahiko Arakawa, Naru Hirata, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Motoo Ito, Eizo Nakamura, Kentaro Uesugi, Katsura Kobayashi, Tatsuhiro Michikami, Hiroshi Kikuchi, Naoyuki Hirata, Yoshiaki Ishihara, Koji Matsumoto, Hirotomo Noda, Rina Noguchi, Yuri Shimaki, Kei Shirai, Kazunori Ogawa, Koji Wada, Hiroki Senshu, Yukio Yamamoto, Tomokatsu Morota, Rie Honda, Chikatoshi Honda, Yasuhiro Yokota, Moe Matsuoka, Naoya Sakatani, Eri Tatsumi, Akira Miura, Manabu Yamada, Atsushi Fujii, Chikako Hirose, Satoshi Hosoda, Hitoshi Ikeda, Takahiro Iwata, Shota Kikuchi, Yuya Mimasu, Osamu Mori, Naoko Ogawa, Go Ono, Takanobu Shimada, Stefania Soldini, Tadateru Takahashi, Yuto Takei, Hiroshi Takeuchi, Ryudo Tsukizaki, Kent Yoshikawa, Fuyuto Terui, Satoru Nakazawa, Satoshi Tanaka, Takanao Saiki, Makoto Yoshikawa, Sei-ichiro Watanabe, Yuichi Tsuda
    NATURE ASTRONOMY 6(2) 214-+ 2022年2月  
    Abstract C-type asteroids1 are considered to be primitive small Solar System bodies enriched in water and organics, providing clues to the origin and evolution of the Solar System and the building blocks of life. C-type asteroid 162173 Ryugu has been characterized by remote sensing2–7 and on-asteroid measurements8,9 with Hayabusa2 (ref. 10). However, the ground truth provided by laboratory analysis of returned samples is invaluable to determine the fine properties of asteroids and other planetary bodies. We report preliminary results of analyses on returned samples from Ryugu of the particle size distribution, density and porosity, spectral properties and textural properties, and the results of a search for Ca–Al-rich inclusions (CAIs) and chondrules. The bulk sample mainly consists of rugged and smooth particles of millimetre to submillimetre size, confirming that the physical and chemical properties were not altered during the return from the asteroid. The power index of its size distribution is shallower than that of the surface boulder observed on Ryugu11, indicating differences in the returned Ryugu samples. The average of the estimated bulk densities of Ryugu sample particles is 1,282 ± 231 kg m−3, which is lower than that of meteorites12, suggesting a high microporosity down to the millimetre scale, extending centimetre-scale estimates from thermal measurements5,9. The extremely dark optical to near-infrared reflectance and spectral profile with weak absorptions at 2.7 and 3.4 μm imply a carbonaceous composition with indigenous aqueous alteration, matching the global average of Ryugu3,4 and confirming that the sample is representative of the asteroid. Together with the absence of submillimetre CAIs and chondrules, these features indicate that Ryugu is most similar to CI chondrites but has lower albedo, higher porosity and more fragile characteristics.
  • Yoshifumi Saito, Dominique Delcourt, Masafumi Hirahara, Stas Barabash, Nicolas André, Takeshi Takashima, Kazushi Asamura, Shoichiro Yokota, Martin Wieser, Masaki N. Nishino, Mitsuo Oka, Yoshifumi Futaana, Yuki Harada, Jean-André Sauvaud, Philippe Louarn, Benoit Lavraud, Vincent Génot, Christian Mazelle, Iannis Dandouras, Christian Jacquey, Claude Aoustin, Alain Barthe, Alexandre Cadu, Andréi Fedorov, Anne-Marie Frezoul, Catherine Garat, Eric Le Comte, Qiu-Mei Lee, Jean-Louis Médale, David Moirin, Emmanuel Penou, Mathieu Petiot, Guy Peyre, Jean Rouzaud, Henry-Claude Séran, Zdenĕk Nĕmec̆ek, Jana S̆afránková, Maria Federica Marcucci, Roberto Bruno, Giuseppe Consolini, Wataru Miyake, Iku Shinohara, Hiroshi Hasegawa, Kanako Seki, Andrew J. Coates, Frédéric Leblanc, Christophe Verdeil, Bruno Katra, Dominique Fontaine, Jean-Marie Illiano, Jean-Jacques Berthelier, Jean-Denis Techer, Markus Fraenz, Henning Fischer, Norbert Krupp, Joachim Woch, Ulrich Bührke, Björn Fiethe, Harald Michalik, Haruhisa Matsumoto, Tomoki Yanagimachi, Yoshizumi Miyoshi, Takefumi Mitani, Manabu Shimoyama, Qiugang Zong, Peter Wurz, Herman Andersson, Stefan Karlsson, Mats Holmström, Yoichi Kazama, Wing-Huen Ip, Masahiro Hoshino, Masaki Fujimoto, Naoki Terada, Kunihiro Keika
    Space Science Reviews 217(5) 2021年8月  
  • Yuichiro Ezoe, Ryu Funase, Harunori Nagata, Yoshizumi Miyoshi, Satoshi Kasahara, Hiroshi Nakajima, Ikuyuki Mitsuishi, Kumi Ishikawa, Junko S. Hiraga, Kazuhisa Mitsuda, Masaki Fujimoto, Munetaka Ueno, Atsushi Yamazaki, Hiroshi Hasegawa, Yosuke Matsumoto, Yasuhiro Kawakatsu, Takahiro Iwata, Hironori Sahara, Yoshiaki Kanamori, Kohei Morishita, Hiroyuki Koizumi, Makoto Mita, Takefumi Mitani, Masaki Numazawa, Landon Kamps, Yusuke Kawabata
    SPACE TELESCOPES AND INSTRUMENTATION 2020: ULTRAVIOLET TO GAMMA RAY 11444 2021年  
    GEO-X (GEOspace X-ray imager) is a 50 kg-class small satellite to image the global Earth's magnetosphere in X-rays via solar wind charge exchange emission. A 12U CubeSat will be injected into an elliptical orbit with an apogee distance of similar to 40 Earth radii. In order to observe the diffuse soft X-ray emission in 0.3-2 keV and to verify X-ray imaging of the dayside structures of the magnetosphere such as cusps, magnetosheaths and magnetopauses which are identified statistically by in-situ satellite observations, an original light-weight X-ray imaging spectrometer (similar to 10 kg, similar to 10 W, similar to 10x10x30 cm) will be carried. The payload is composed of a ultra light-weight MEMS Wolter type-I telescope (similar to 4x4 deg(2) FOV, <10 arcmin resolution) and a high speed CMOS sensor with a thin optical blocking filter (similar to 2x2 cm(2), frame rate similar to 20 ms, energy resolution <80 eV FWHM at 0.6 keV). An aimed launch year is 2023-25 corresponding to the 25th solar maximum.
  • Go Murakami, Hajime Hayakawa, Hiroyuki Ogawa, Shoya Matsuda, Taeko Seki, Yasumasa Kasaba, Yoshifumi Saito, Ichiro Yoshikawa, Masanori Kobayashi, Wolfgang Baumjohann, Ayako Matsuoka, Hirotsugu Kojima, Satoshi Yagitani, Michel Moncuquet, Jan-Erik Wahlund, Dominique Delcourt, Masafumi Hirahara, Stas Barabash, Oleg Korablev, Masaki Fujimoto
    Space Science Reviews 216(7) 2020年10月  
もっとみる

MISC

 108
  • M Fujimoto, MS Nakamura, T Nagai, T Mukai, T Yamamoto, S Kokubun
    GEOPHYSICAL RESEARCH LETTERS 23(18) 2533-2536 1996年9月  
    An anomalously large southward Bz (-23 nT) is detected in association with tailward jet (1600 km/s) by GEOTAIL at X(GSM) = -46 R(E). Variations of MHD parameters suggest that the large southward Bz is caused by piling-up of reconnected field lines by the jet against the standing plasma sheet. In addition, the ion distribution at the time of the large southward Bz is found to show a counter streaming ions (CSI) feature. A hybrid simulation of a reconnection process not only reproduces this feature, but also proves that the CSI ions are from both the lobes. Taking this CSI feature as new kinetic evidence that both the lobes are magnetically connected, we firmly conclude that the event is interpreted in terms of near-Earth reconnection.
  • M FUJIMOTO, T TERASAWA
    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 100(A7) 12025-12033 1995年7月  
    Hybrid code simulations of the MHD scale Kelvin-Helmholtz (K-H) instability have been conducted. In contrast to the homogeneous background case where the large-scale ion mixing across the shear layer occurs inside the vortex obeying the hydrodynamic similarity law, the ion mixing is found to be reduced when the background magnetic field is inhomogeneous. This stabilization effect is twofold: it is an ion kinetic effect which reduces the saturation vortex size and so the mixing length when the shear layer width and the wavelength of the growing mode are small. The reduction effect still works even when the shear layer width/wavelength are large and a well defined vortical motion as in the fluid model is evident. The mixing is suppressed for this case because the ions on the lower magnetic field (magnetosheath) side cannot enter within the vortex island: The rolled-up magnetopause current sheet block them out electrostatically. The geophysical implication of the present result is that the K-H mixing alone may not be as efficient as to produce the large-scale mixing blob of the low-latitude boundary layer (LLBL) when the magnetic field intensity is highly different across the magnetopause.
  • M FUJIMOTO, T TERASAWA
    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 100(A7) 12025-12033 1995年7月  
    Hybrid code simulations of the MHD scale Kelvin-Helmholtz (K-H) instability have been conducted. In contrast to the homogeneous background case where the large-scale ion mixing across the shear layer occurs inside the vortex obeying the hydrodynamic similarity law, the ion mixing is found to be reduced when the background magnetic field is inhomogeneous. This stabilization effect is twofold: it is an ion kinetic effect which reduces the saturation vortex size and so the mixing length when the shear layer width and the wavelength of the growing mode are small. The reduction effect still works even when the shear layer width/wavelength are large and a well defined vortical motion as in the fluid model is evident. The mixing is suppressed for this case because the ions on the lower magnetic field (magnetosheath) side cannot enter within the vortex island: The rolled-up magnetopause current sheet block them out electrostatically. The geophysical implication of the present result is that the K-H mixing alone may not be as efficient as to produce the large-scale mixing blob of the low-latitude boundary layer (LLBL) when the magnetic field intensity is highly different across the magnetopause.
  • 中村 正人, 河野 英昭, 藤本 正樹, 中川 朋子, 長野 勇, 八木谷 聡, 寺沢 敏夫
    遊・星・人 : 日本惑星科学会誌 4(2) 100-107 1995年6月25日  
  • M FUJIMOTO, M NAKAMURA
    GEOPHYSICAL RESEARCH LETTERS 21(25) 2955-2958 1994年12月  
    The acceleration process of minor heavy ions in the magnetotail reconnection layer is studied by 1D hybrid simulations. In the plasma sheet, different acceleration mechanisms are found to be operative according to the heavy ion mass, not only because of their different inertia but also because of the evolutions of different downstream states. Despite this difference, the ions, including the major protons, are accelerated up to the maximum velocity of twice the lobe Alfven velocity: the energy gain is proportional to the ion mass.
  • M FUJIMOTO, M NAKAMURA
    GEOPHYSICAL RESEARCH LETTERS 21(25) 2955-2958 1994年12月  
    The acceleration process of minor heavy ions in the magnetotail reconnection layer is studied by 1D hybrid simulations. In the plasma sheet, different acceleration mechanisms are found to be operative according to the heavy ion mass, not only because of their different inertia but also because of the evolutions of different downstream states. Despite this difference, the ions, including the major protons, are accelerated up to the maximum velocity of twice the lobe Alfven velocity: the energy gain is proportional to the ion mass.
  • M FUJIMOTO, T TERASAWA
    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 99(A5) 8601-8613 1994年5月  
    Hybrid code simulations (ion particles, charge neutralizing electron fluid) of the MHD scale transverse Kelvin-Helmholtz (K-H) instability in a uniform plasma have been conducted. On a macroscopic scale the saturation states are found to be similar to the MHD result, even if the initial shear layer half thickness is as thin as twice the ion thermal Larmor radius. However, as opposed to the conventional belief based on the frozen-in concept that a large-scale mixing will be prohibited, an enhanced mixing of ions across the shear layer is found to occur inside the vortex. The temporal/spatial scales of the mixing process are determined by the fluid dynamical parameters and are anomalously quick/large compared to what can result from the mixing due to the finite Larmor radius overlapping at the interface. We propose that the low latitude boundary layer just inside the magnetopause is the mixing layer formed possibly by this mechanism.
  • J.Geophys.Res. 99(A5) 8601-8613 1994年  

書籍等出版物

 14
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所属学協会

 3

Works(作品等)

 1

共同研究・競争的資金等の研究課題

 25
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学術貢献活動

 3

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 1
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