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  2. 村上 豪

村上 豪

ムラカミ ゴウ  (Go Murakami)

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 助教
J-GLOBAL ID
201901001752900088
researchmap会員ID
B000359749

研究キーワード

 7

研究分野

 3

経歴

 4

学歴

 3

主要な受賞

 7
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論文

 146
  • G. Kinoshita, H. Ueno, G. Murakami, M. Pinto, K. Yoshioka, Y. Miyoshi
    Journal of Geophysical Research: Space Physics 130(1) 2024年12月27日  査読有り
    Abstract Although primarily a housekeeping instrument for measuring ambient radiation, the Solar Particle Monitor (SPM) onboard BepiColombo can measure high‐energy particles, making it useful for observing phenomena such as galactic cosmic rays and Solar Energetic Particles (SEPs). However, it only records time‐series data of particle energy loss and counts, which requires characterization by radiation simulation for scientific analysis. In this study, a physical model of the SPM was constructed using the “Geant4” radiation simulation toolkit to investigate its response to charged particles. The probability density functions were derived from the response functions to indicate the proportion of particles in each energy range among the SPM counts. Finally, we inverse‐calculated the flux from the counts in the corresponding energy ranges. We applied this method to data from the terrestrial radiation belt and SEPs in March 2022. The results agreed with the empirical radiation belt model and another instrument onboard BepiColombo, demonstrating the validity of the method. This study highlights the potential for scientific applications of housekeeping instruments and suggests the broader use of similar methods on other missions for expanding inner heliosphere multi‐point exploration.
  • Shotaro Sakai, Hiromu Nakagawa, Justin Deighan, Sonal K. Jain, Kei Masunaga, Fuminori Tsuchiya, Naoki Terada, Majd Mayyasi, Nicholas M. Schneider, David L. Mitchell, Christian Mazelle, Mehdi Benna, Robert J. Lillis, Go Murakami, Shannon M. Curry, Kanako Seki
    The Astrophysical Journal 977(2) 226-226 2024年12月1日  
    Abstract C+ emission is generated by electron impact, dissociative ionization, photoionization, and resonant scattering with carbon-related atoms, molecules, and ions in the Martian ionosphere and thermosphere. The contribution of each mechanism to the emission, however, has not been elucidated due to the difficulty of observation and the fact that a part of the emission cross section is unclear. The current paper isolates the C+ emission mechanism using remote-sensing and in situ observations on board Mars Atmosphere and Volatile EvolutioN. Both electron impact and dissociative ionization/photoionization contribute to C+ emission below 150 km altitude when the CO density is high, but only dissociative ionization/photoionization contributes to the emission for the low CO density case, while only dissociative ionization/photoionization dominates the emission at altitudes between 150 and 165 km for both CO density cases. It is difficult to estimate the total flux of suprathermal electrons in the ionosphere from remote-sensing observations of C+ emission because the contribution of electron impact to C+ emission is small. In contrast, C-atom remote-sensing observations might provide a better understanding of the total flux of suprathermal electrons in the ionosphere than C+ emission, and global ultraviolet observations could be utilized as a tool for monitoring the ionosphere. The total flux of suprathermal electrons estimated from C-atom emission may be utilized to isolate the contribution of each C+ emission process to the brightness more accurately. This suggests that the C+ and C-atom emissions might be tracers of spatiotemporal variations in the Martian ionosphere and thermosphere.
  • Y. Suzuki, E. Quémerais, J.‐Y. Chaufray, R. Robidel, G. Murakami, F. Leblanc, K. Yoshioka, I. Yoshikawa, O. Korablev
    Journal of Geophysical Research: Planets 129(10) 2024年10月16日  査読有り
    Abstract Mercury's exosphere is an important target for understanding the dynamics of coupled systems in space environments, tenuous planetary atmospheres, and planetary surfaces. Magnesium (Mg) is especially crucial for establishing methods for estimating the surface chemical composition distribution through observations of the exosphere because its distribution in the exosphere and on the surface is strongly correlated. However, owing to its low radiance, the Hermean Mg exosphere has only been detected by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft. Thus, we have few observation data for areas other than low latitude regions in addition to few detection cases of short‐term or sporadic fluctuations, resulting in a poor understanding of ejection and transportation mechanisms of the Mg exosphere. In this study, we analyzed the distribution of the Hermean Mg exosphere by the Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS) onboard the Mercury Planetary Orbiter of the BepiColombo mission during its second and third Mercury swing‐bys (MSBs). First, we constructed a calibration method including background subtraction and calibration using stellar observations. Mg light curves at two true anomaly angles were obtained, which were in agreement with the Chamberlain model and a three‐dimensional numerical calculation. Comparing the Mg and calcium (Ca) radiances obtained by PHEBUS during the MSBs, the exospheric Mg atoms have a lower energy than the exospheric Ca atoms. This is consistent with the lower energy necessary for producing the Mg atoms produced by molecular photodissociation than for Ca atoms.
  • Lina Z. Hadid, Dominique Delcourt, Yuki Harada, Mathias Rojo, Sae Aizawa, Yoshifumi Saito, Nicolas André, Austin N. Glass, Jim M. Raines, Shoichiro Yokota, Markus Fränz, Bruno Katra, Christophe Verdeil, Björn Fiethe, Francois Leblanc, Ronan Modolo, Dominique Fontaine, Norbert Krupp, Harald Krüger, Frédéric Leblanc, Henning Fischer, Jean-Jacques Berthelier, Jean-André Sauvaud, Go Murakami, Shoya Matsuda
    Communications Physics 7(1) 2024年10月3日  
  • Yuki Harada, Yoshifumi Saito, Lina Z. Hadid, Dominique Delcourt, Sae Aizawa, Mathias Rojo, Nicolas André, Moa Persson, Markus Fraenz, Shoichiro Yokota, Andréi Fedorov, Wataru Miyake, Emmanuel Penou, Alain Barthe, Jean‐André Sauvaud, Bruno Katra, Shoya Matsuda, Go Murakami
    Journal of Geophysical Research: Space Physics 129(8) 2024年8月2日  
    Abstract Although solar wind‐driven convection is expected to dominate magnetospheric circulation at Mercury, its exact pattern remains poorly characterized by observations. Here we present BepiColombo Mio observations during the third Mercury flyby indicative of convection‐driven transport of low‐energy dense ions into the deep magnetosphere. During the flyby, Mio observed an energy‐dispersed ion population from the duskside magnetopause to the deep region of the midnight magnetosphere. A comparison of the observations with backward test particle simulations suggests that the observed energy dispersion structure can be explained in terms of energy‐selective transport by convection from the duskside tail magnetopause. We also discuss the properties and origins of more energetic ions observed in the more dipole‐like field regions of the magnetosphere in comparison to previously reported populations of the plasma sheet horn and ring current ions. Additionally, forward test particle simulations predict that most of the observed ions on the nightside will precipitate onto relatively low‐latitude regions of the nightside surface of Mercury for a typical convection case. The presented observations and simulation results reveal the critical role of magnetospheric convection in determining the structure of Mercury's magnetospheric plasma. The upstream driver dependence of magnetospheric convection and its effects on other magnetospheric processes and plasma‐surface interactions should be further investigated by in‐orbit BepiColombo observations.
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MISC

 118
  • Fuminori Tsuchiya, Yasumasa Kasaba, Ichiro Yoshikawa, Go Murakami, Atsushi Yamazaki, Kazuo Yoshioka, Tomoki Kimura, Chihiro Tao, Ryoichi Koga, Hajime Kita, Kei Masunaga, Masato Kagitani, Shotaro Sakai, Masaki Kuwabara
    Abstract EGU 2023 2023年5月15日  招待有り
    Hisaki is an earth orbiting extreme ultraviolet spectroscope dedicated for observing solar system planets. Thanks to its monitoring capability, Hisaki has carried out unprecedented continuous observation of Io plasma torus, Jovian aurora, and Mars and Venus upper atmosphere since December 2013. One of notable phenomena observed by Hisaki is significant enhancements of neutral gas (sodium and oxygen) from Io occurred in the spring of 2015. Hisaki revealed that not only the plasma source, but transport, heating, and loss processes of magnetospheric plasma were influenced by the variation in the neutral source input. The presentation will include related topics from recent Hisaki publication. Since the autumn of 2016, the Juno spacecraft was in the orbit around Jupiter. Hisaki monitored activities of Jovian aurora and the plasma torus in the Juno era. These datasets will provide opportunities to compare in-situ observation by Juno with the global view by Hisaki. JAXA approved the Hisaki mission period by the end of March 2023. As a future remote observation platform, we are going to propose a UV space telescope, LAPYUTA (Life-environmentology, Astronomy, and PlanetarY Ultraviolet Telescope Assembly), a Japanese-leading mission using heritages of UV instruments for planetary science (e.g., Hisaki) and space telescope techniques for astronomy. One of goals of this mission is dynamics of our solar system planets and moons as the most quantifiable archetypes of extraterrestrial habitable environments in the universe. Water plume that gushes from the subsurface ocean of Galilean moons and tenuous atmosphere which is generated by bombardment of energetic charged particles to the surface are primary targets of LAPYUTA. As the plume activity and the atmosphere are not stable, continuous monitoring with high spatial resolution is essential. The icy moon's plume and ambient space will be deeply explored with the spacecraft by NASA's and ESA's icy moon missions in 2020s-2030s. The complementary remote sensing by LAPYUTA will visualize their global structure and temporal dynamics.
  • Yudai Suzuki, Kazuo Yoshioka, Kei Masunaga, Hideyo Kawakita, Yoshiharu Shinnaka, Go Murakami, Tomoki Kimura, Fuminori Tsuchiya, Atsushi Yamazaki, Ichiro Yoshikawa
    2023年2月26日  
  • Kei Masunaga, Naoki Terada, Nao Yoshida, Yuki Nakamura, Takeshi Kuroda, Kazuo Yoshioka, Yudai Suzuki, Hiromu Nakagawa, Tomoki Kimura, Fuminori Tsuchiya, Go Murakami, Atsushi Yamazaki, Tomohiro Usui, Ichiro Yoshikawa
    2023年2月22日  
  • 今村 剛, 村上 豪, 岩井 一正, 三好 由純, 塩田 大幸
    日本惑星科学会誌遊星人 30(3) 105-106 2021年9月25日  
    2021年3月から4月にかけて，あかつきと水星探査機BepiColomboが地球から見て太陽のほぼ反対側を同時に通過する貴重な機会があり，これを活かして2 機が協調して太陽コロナの電波掩蔽観測を実施した．太陽観測衛星ひのでによる太陽表面の観測も同時に行い，コロナ研究のためのユニークなデータセットが得られた．
  • Kasaba Yasumasa, Takashima Takeshi, Matsuda Shoya, Eguchi Sadatoshi, Endo Manabu, Miyabara Takeshi, Taeda Masahiro, Kuroda Yoshikatsu, Kasahara Yoshiya, Imachi Tomohiko, Kojima Hirotsugu, Yagitani Satoshi, Moncuquet Michel, Wahlund Jan-Erik, Kumamoto Atsushi, Matsuoka Ayako, Baumjohann Wolfgang, Yokota Shoichiro, Asamura Kazushi, Saito Yoshifumi, Delcourt Dominique, Hirahara Masafumi, Barabash Stas, Andre Nicolas, Kobayashi Masanori, Yoshikawa Ichiro, Murakami Go, Hayakawa Hajime
    Space Science Reviews 216(3) 2020年  
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共同研究・競争的資金等の研究課題

 11
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