Three‐dimensional Hall MHD simulation of lunar minimagnetosphere: General characteristics and comparison with Chang'E‐2 observations

Lunar minimagnetosphere formed by the interaction between the solar wind and a local crustal field often has a scale size comparable to the ion inertia length, in which the Hall effect is very important. In this paper, the general characteristics of lunar minimagnetosphere are investigated by three-dimensional Hall MHD simulations. It is found that the solar wind ions can penetrate across the magnetopause to reduce the density depletion and cause the merging of the shock and magnetopause, but the electrons are still blocked at the boundary. Besides, asymmetric convection occurs, resulting in the magnetic field piles up on one side while the plasma gathers on the other side. The size of the minimagnetosphere is determined by both the solar zenith angle and the magnetosonic Mach number, while the Hall effect is determined by the ratio of the pressure balance distance to the ion inertia length. When the ratio gets small, the shock may disappear. Finally, we present a global Hall MHD simulation for comparison with the observation from Chang'E-2 satellite on 11 October 2010 and confirm that Chang'E-2 flew across compression regions of two separate minimagnetospheres.