Earth Planets Space, Vol. 58 (No. 5), pp. e17-e20, 2006E-LETTER
Tomoko Nakagawa1 and Masahide Iizima2
1Tohoku Institute of Technology, 35-1 Yagiyama Kasumi-cho, Taihaku-ku, Sendai, Miyagi 982-8577, Japan
2Tohoku University, Aramaki Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
(Received February 21, 2006; Revised March 23, 2006; Accepted April 3, 2006; Online published April 28, 2006)
Velocity distribution of the solar wind electrons injected into the lunar wake boundary is re-examined by using a simple model structure of inward electric field. The electrons that were flowing along the magnetic field lines undergo pitch angle scattering due to the electric field component perpendicular to the magnetic field. The electrons obtain perpendicular speeds twice as much as the drift speed. On the basis of the GEOTAIL observations of the whistler mode waves and strahl electrons, the intensity of the electric field and the thickness of the wake structure are estimated to be 28-40 mVm-1 and less than 20 km, respectively.
Key words: Lunar wake, pitch angle diffusion, electric field, wake potential structure, electron distribution function.