Global Hall MHD Simulations of the Solar Wind Implantation Flux on the Lunar Surface

Abstract

The solar wind can directly interact with the lunar surface and provide an important source for surface space weathering and water generation. Here we study the solar wind implantation flux on the lunar surface with global Hall MHD simulations. The shielding effects of both the Earth’s magnetosphere and lunar magnetic anomalies are considered. It is found that a large-scale lunar mini-magnetosphere can be caused by the solar wind interaction with the magnetic anomalies on the lunar far side, which causes a large shielding area on the surface. In addition, the Earth’s magnetosphere brings a longitudinal variation in the implantation flux, with minimum fluxes at 0° longitude. With the integrated flux over a lunation, we find that there are some local cavities on the implantation flux map, which are colocated with both the magnetic anomalies and the lunar swirls. Further studies show that there is a south–north asymmetry in the implantation flux, which can be used to explain the lower water content observed in the southern hemisphere. Our results provide a global map of the solar wind implantation flux on the lunar surface and are useful for evaluating the large-scale effect of solar wind implantation and sputtering on the space weathering and the water or gas generation of the surface.