Properties of plasma near the moon in the magnetotail

Abstract

Plasma physical processes near the lunar surface depend on the properties of the ambient plasma. However, the Moon spends almost half of its time downstream of the Earth׳s bow shock where the plasma near the Moon is anticipated to differ from the undisturbed solar wind. We have made statistical analysis of plasma parameters and the magnetic field near the orbit of Moon by using a global magnetohydrodynamic simulation made for a time period which covers a full year. The study shows that the velocity and the magnetic field downstream of the bow shock near the lunar orbit are much alike in the solar wind. This suggests that these plasma parameters near the Moon is controlled and driven by the solar wind. Density and temperature of the plasma are, however, strongly modified by the Earth. Consequently, the characteristic length scale of the plasma layer above the lunar surface, the Debye length, is controlled by plasma physical processes in the Earth׳s magnetosphere. The derived plasma and field parameters make it possible to analyse in detail the direct plasma-surface interaction at the Moon when it is in the magnetotail.