TERRAPUB Earth, Planets and Space
Back

Earth Planets Space, Vol. 64 (No. 2), pp. 83-92, 2012
doi:10.5047/eps.2011.07.011

Simultaneous observation of the electron acceleration and ion deceleration over lunar magnetic anomalies

Yoshifumi Saito1, Masaki N. Nishino1, Masaki Fujimoto1, Tadateru Yamamoto1, Shoichiro Yokota1, Hideo Tsunakawa2, Hidetoshi Shibuya3, Masaki Matsushima2, Hisayoshi Shimizu4, and Futoshi Takahashi2

1Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
2Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
3Kumamoto University, 2-39-1, Kurokami, Kumamoto 860-8555, Japan
4Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan

(Received March 14, 2011; Revised July 4, 2011; Accepted July 19, 2011; Online published March 8, 2012)

Abstract: At ∼25 km altitude over magnetic anomalies on the Moon, the deceleration of the solar wind ions, acceleration of the solar wind electrons parallel to the magnetic field, and heating of the ions reflected by magnetic anomalies were simultaneously observed by MAP-PACE on Kaguya. Deceleration of the solar wind ions was observed for two major solar wind ion compositions: protons and alpha particles. Deceleration of the solar wind had the same ΔE/qE: deceleration energy, q: charge) for both protons and alpha particles. In addition, the acceleration energy of the electrons was almost the same as the deceleration energy of the ions. This indicates the existence of an anti-moonward electric field over the magnetic anomaly above the altitude of Kaguya. The reflected ions were observed in a much larger area than the area where magnetic field enhancement was observed. These reflected ions had a higher temperature and lower bulk velocity than the incident solar wind ions. This suggests the existence of a non-adiabatic dissipative interaction between solar wind ions and lunar magnetic anomalies below Kaguya.
Key words: Moon, plasma, magnetic anomaly, solar wind.


Corresponding author E-mail: saito@stp.isas.jaxa.jp


[Full text] (PDF 1.6 MB)