Yoshifumi Futaana
Swedish Institute of Space Physics
Abstract
In this talk, we will review structures and physics of the plasma wake formed behind the Moon in the solar wind. The Moon has many characteristics that contribute to make the solar wind interaction different from that with other solar system bodies such as Earth, Mars, Venus, Mercury or asteroids: 1) the Moon has no global magnetic field, 2) the Moon has very low conductance, 3) the Moon absorbs most of the solar wind protons at its surface, and 4) the Moon is larger than the proton gyro-radius in the solar wind. Therefore, no global-scale bow shock or magnetosphere can be formed in front of the Moon. Instead, a very high vacuum region called a "wake" is formed behind the Moon. While the solar wind plasma that flew beside the lunar terminator diffuses into the wake, it has been thought that the diffusion could be formulated by a simple model of plasma expansion into the vacuum. However in the 1990s, WIND, Geotail and Nozomi observed dynamic features close to or inside the lunar wake from their flyby measurements and investigations. Moreover, Lunar Prospector, Chang'E-1, Kaguya, and Chandrayaan-1 have recently been inserted into low-altitude lunar orbit, and provide excellent datasets for understanding the dynamics of the lunar wake. Our knowledge about the lunar wake has thus increased greatly in recent years. We will review these observational results and try to compare them with existing theories and numerical simulations that have been developed to understand the lunar wake.
Created 2010-12-02 13:11:40 by Mats Holmström Last changed 2011-01-19 11:40:17 by Mats Holmström
