[P-CG19] 惑星大気圏・電磁圏

[PCG19-P09] A potential magnetic reconnection signature on the lunar crustal magnetic field: Kaguya low-altitude observations

*荻野 晃平¹、原田 裕己¹、西野 真木²、斎藤 義文²、横田 勝一郎³、高橋 太⁴、清水 久芳⁷、笠原 禎也⁶、熊本 篤志⁵ (1.京都大学大学院理学研究科、2.国立研究開発法人宇宙航空研究開発機構、3.大阪大学理学研究科、4.九州大学理学研究院、5.東京大学地震研究所 、6.金沢大学学術創成センター、7.東北大学理学研究科)

キーワード：月、プラズマ、磁気リコネクション、ミニ磁気圏

The Moon has no global intrinsic magnetic field, while the solar wind interaction with lunar crustal magnetic anomalies (LMAs) forms lunar mini-magnetospheres. Recent ARTEMIS observations and 2D fully kinetic simulations suggested the occurrence of magnetic reconnection on LMAs (Sawyer et al., 2023; Stanier et al., 2024). Since magnetic reconnection plays a fundamental role in the dynamics of space plasma, by changing magnetic field topology and converting magnetic energy into charged particle energy, magnetic reconnection on LMAs could affect the plasma environment around the moon. However, since the vertical spatial scales of LMAs are small, below several tens of kilometers, it is challenging to directly observe the interaction regions from typical nominal altitudes of lunar orbiters (~100 km) and the details of magnetic reconnection on LMAs have not been fully understood. In this study, we analyze low-altitude data of charged particles and electromagnetic fields obtained by Kaguya. We identified a current sheet crossing from magnetic field data as well as simultaneous characteristic energy variations of electrons from the observed electron velocity distribution. As electron-only magnetic reconnection on sub-ion-scale LMAs (Stanier et al., 2024) could be accompanied by electron outflow jets (Phan et al., 2018), we discuss the possibility that the current sheet-crossing event can be an indicator of the occurrence of magnetic reconnection on the LMA.