2013年10月
Type-II entry of solar wind protons into the lunar wake: Effects of magnetic connection to the night-side surface
PLANETARY AND SPACE SCIENCE
- 巻
- 87
- 号
- 開始ページ
- 106
- 終了ページ
- 114
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1016/j.pss.2013.08.017
- 出版者・発行元
- PERGAMON-ELSEVIER SCIENCE LTD
Our recent observations around the Moon revealed that so-called type-II (T2) entry of the solar wind protons into the near-Moon wake occurs when the IMF is dominated by the non-radial components (i.e. By and/or B-z). Under this condition a part of the solar wind protons scattered/reflected at the lunar dayside surface subsequently enters the central region of the near-Moon wake after a large-scale cycloid motion, which accelerates electrons along the filed line into the wake. The situation handled in the previous studies is that the relevant magnetic field line is detached from the lunar surface, leaving a possibility of the 12 entry under magnetic connection left open. Here we report that the protons can access the central wake region that is magnetically connected to the lunar nightside surface, which we categorize into the T2 entry with magnetic connection to the lunar surface (T2MC). Furthermore we show that the energy of the electron beams induced by the proton entry into the wake depends on the magnetic connectivity. Strong electron acceleration (up to several hundred eV to 1 key) along the magnetic field associated with the 12 entry is prominent when the field line has its both ends in the solar wind, that is, when the magnetic field is detached from the lunar surface (i.e. the previously reported 12 entry that we rename to T2MD). On the other hand, no significant electron acceleration is found in the T2MC cases, although an enhancement of the electron flux associated with the T2 proton entry is evident. We also report that the T2 entry process takes place even under radial (B-X-dominated) IMF condition. Our results indicate that, while the 12 entry of solar wind protons into the wake itself does not require a special IMF condition but is a rather general phenomenon, the characteristic energy of associated electrons does show a strong dependence on the magnetic connectivity to the lunar surface. (C) 2013 Elsevier Ltd. All rights reserved.
- リンク情報
- ID情報
-
- DOI : 10.1016/j.pss.2013.08.017
- ISSN : 0032-0633
- J-Global ID : 201402283440640986
- Web of Science ID : WOS:000327810100011