Abstract
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.
| Original language | English |
|---|---|
| Article number | 113392 |
| Journal | Icarus |
| Volume | 335 |
| DOIs | |
| Publication status | Published - Jan 1 2020 |
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All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Cite this
Decrease of the interplanetary magnetic field strength on the lunar dayside and over the polar region. / Nishino, Masaki N.; Saito, Yoshifumi; Tsunakawa, Hideo; Harada, Yuki; Takahashi, Futoshi; Yokota, Shoichiro; Matsushima, Masaki; Shibuya, Hidetoshi; Shimizu, Hisayoshi; Miyashita, Yukinaga.
In: Icarus, Vol. 335, 113392, 01.01.2020.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Decrease of the interplanetary magnetic field strength on the lunar dayside and over the polar region
AU - Nishino, Masaki N.
AU - Saito, Yoshifumi
AU - Tsunakawa, Hideo
AU - Harada, Yuki
AU - Takahashi, Futoshi
AU - Yokota, Shoichiro
AU - Matsushima, Masaki
AU - Shibuya, Hidetoshi
AU - Shimizu, Hisayoshi
AU - Miyashita, Yukinaga
PY - 2020/1/1
Y1 - 2020/1/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85070212486&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85070212486&partnerID=8YFLogxK
U2 - 10.1016/j.icarus.2019.113392
DO - 10.1016/j.icarus.2019.113392
M3 - Article
AN - SCOPUS:85070212486
VL - 335
JO - Icarus
JF - Icarus
SN - 0019-1035
M1 - 113392
ER -