Decrease of the interplanetary magnetic field strength on the lunar dayside and over the polar region

Masaki N. Nishino, Yoshifumi Saito, Hideo Tsunakawa, Yuki Harada, Futoshi Takahashi, Shoichiro Yokota, Masaki Matsushima, Hidetoshi Shibuya, Hisayoshi Shimizu, Yukinaga Miyashita

研究成果: Contribution to journalArticle査読

抄録

The Moon interacts with the incident solar wind plasma in various ways, and most of these interactions are accompanied by variations of the interplanetary magnetic field (IMF) around the Moon. Here we first report decreases of the IMF strength observed at 100 km altitude on the lunar dayside and over the polar region, comparing upstream solar wind data from ACE with Kaguya (SELENE) data. We note that the magnetic field decreases are observed above non-magnetized regions or very weakly magnetized regions. In one event the IMF is weakened in the dayside northern hemisphere when the IMF is roughly anti-parallel to the solar wind flow. We estimate that the decrease in the magnetic pressure can be partly compensated by the thermal pressure of the back-scattered solar wind protons, which suggests that the magnetic field decrease is interpreted as diamagnetic effect by the back-scattered protons. In another event an IMF decrease is continuously detected from the northern polar region to the dayside mid-latitude region, which is not fully explained by the thermal pressure of the back-scattered protons. We also discuss the diamagnetic current system in the upstream (fore-moon) solar wind region formed by the back-scattered protons.

本文言語英語
論文番号113392
ジャーナルIcarus
335
DOI
出版ステータス出版済み - 1 1 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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