Japan Geoscience Union Meeting 2025

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[J] Poster

P (Space and Planetary Sciences ) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM16] Heliosphere and Interplanetary Space

Mon. May 26, 2025 5:15 PM - 7:15 PM Poster Hall (Exhibition Hall 7&8, Makuhari Messe)

convener:Kazumasa Iwai(Institute for Space–Earth Environmental Research (ISEE), Nagoya University), Yasuhiro Nariyuki(Faculty of Education, University of Toyama), Masaki N Nishino(Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science), Ken Tsubouchi(University of Electro-Communications)

5:15 PM - 7:15 PM

[PEM16-P05] Preliminary results of ENA data analysis on a lunar magnetic anomaly in the terrestrial magnetosheath

*Masahisa Kato1, Yuki Harada1, Yoshifumi Futaana2, Stas Barabash2, Martin Wieser2, Peter Wurz3, Anil Bhardwaj4, Kazushi Asamura5 (1.Kyoto University, 2.Institutet för Rymdfysik, 3.University of Bern, 4.Physical Research Laboratory, 5.Japan Aerospace Exploration Agency)


Keywords:The Moon, Energetic Neutral Atoms (ENAs), Crustal magnetic field regions on the lunar surface

Since the Moon does not possess a thick atmosphere, its ambient plasma directly interacts with the lunar surface. The emission of Energetic Neutral Atoms (ENAs) from the lunar surface is one of the phenomena caused by the surface-plasma interaction resulting from backscattering and neutralization of incident ions. Although there is no global dipole-like magnetic field on the Moon, there are locally magnetized regions on the lunar surface. According to previous studies, spatial distributions of ENAs emitted from the lunar surface reflect the non-uniform distributions of solar wind proton precipitation to magnetized regions. The ENA emission has been used for mapping the magnetized region in the solar wind, while recent studies indicate that the measured characteristics of the ENAs contain valuable information to understand the formation of the mini-magnetosphere, which is formed above an anomaly. In this study, we focus on Chandrayaan-1 ENA observations when the Moon is in the terrestrial magnetosheath, to understand the mini-magnetosphere physics under the thermalized, hot plasma. We observed a reduction in the emitted ENAs above the Reiner Gamma magnetic anomaly when the Moon was in the magnetosheath. Characteristics of the anomaly are consistent with the previously reported magnetic shielding of the lunar surface in the solar wind. In this presentation, we report the characteristics of the ENA emission with a focus on the differences and similarities between the solar wind and magnetosheath.