TY - JOUR
T1 - Control of lunar external magnetic enhancements by IMF polarity
T2 - A case study
AU - Nishino, Masaki N.
AU - Fujimoto, Masaki
AU - Tsunakawa, Hideo
AU - Matsushima, Masaki
AU - Shibuya, Hidetoshi
AU - Shimizu, Hisayoshi
AU - Takahashi, Futoshi
AU - Saito, Yoshifumi
AU - Yokota, Shoichiro
N1 - Funding Information:
The authors thank the principal investigators of ACE spacecraft for providing the solar wind data via CDAWeb. The Lunar Prospector MAG data were provided through NASA Planetary Data System (PDS). The authors also wish to express their grateful thanks to all the system members of the SELENE project. This work was supported by Grant-in-Aid for Young Scientists (B) No. 23740375 from Japan Society for the Promotion of Science (JSPS).
Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2012/12
Y1 - 2012/12
N2 - We study an interaction between the solar wind and crustal magnetic fields on the lunar surface using SELENE (Kaguya) data. It has been known that magnetic enhancements are at times detected near the limb external to the lunar wake, which is thus called lunar external magnetic enhancement (LEME), as a result of direct interaction between the solar wind and lunar crustal fields. Although previous observational studies showed that LEMEs in the high solar zenith angle region favor stronger interplanetary magnetic field (IMF) and higher solar wind density, the relation between the IMF and the crustal field orientation has not been taken into account. We show evidence that the relation between the IMF and crustal field orientation is also one of the key factors that control the extent of LEME, focusing on one-day observations at 100 km altitude that include data above strong crustal fields around South Pole-Aitken (SPA) basin. Strong LEMEs are detected at 100 km altitude around SPA basin under the stronger and northward IMF condition, while they weaken under southward IMF. All LEME's peaks are located in the region where unperturbed crustal fields at 300 km altitude are directed northward while they are less related to unperturbed crustal fields at 100 km or lower, which suggests that lunar crustal fields are compressed by the solar wind dynamic pressure, and its large scale component parallel to the IMF is essential to the formation of the LEME.
AB - We study an interaction between the solar wind and crustal magnetic fields on the lunar surface using SELENE (Kaguya) data. It has been known that magnetic enhancements are at times detected near the limb external to the lunar wake, which is thus called lunar external magnetic enhancement (LEME), as a result of direct interaction between the solar wind and lunar crustal fields. Although previous observational studies showed that LEMEs in the high solar zenith angle region favor stronger interplanetary magnetic field (IMF) and higher solar wind density, the relation between the IMF and the crustal field orientation has not been taken into account. We show evidence that the relation between the IMF and crustal field orientation is also one of the key factors that control the extent of LEME, focusing on one-day observations at 100 km altitude that include data above strong crustal fields around South Pole-Aitken (SPA) basin. Strong LEMEs are detected at 100 km altitude around SPA basin under the stronger and northward IMF condition, while they weaken under southward IMF. All LEME's peaks are located in the region where unperturbed crustal fields at 300 km altitude are directed northward while they are less related to unperturbed crustal fields at 100 km or lower, which suggests that lunar crustal fields are compressed by the solar wind dynamic pressure, and its large scale component parallel to the IMF is essential to the formation of the LEME.
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U2 - 10.1016/j.pss.2012.09.011
DO - 10.1016/j.pss.2012.09.011
M3 - Article
AN - SCOPUS:84870620915
VL - 73
SP - 161
EP - 167
JO - Planetary and Space Science
JF - Planetary and Space Science
SN - 0032-0633
IS - 1
ER -