Hybrid Simulations of Solar Wind Plasma Interaction with the Lunar Reiner Gamma Magnetic Anomaly

Abstract: The Moon has small scale regions of strong magnetic fields scattered over its surface, known as crustal fields. Coexisting with some of the strongest crustal fields are peculiar markings in the lunar soil, called lunar swirls, which are suggested to be formed by magnetosphere-like interactions between the crustal fields and the solar wind plasma. This interaction depends on the lunar phase and the Interplanetary Magnetic Field (IMF) among many other parameters (e.g. solar wind dynamic pressure). The focus of this thesis is on a localized crustal field on the lunar near side known as Reiner Gamma, which has distinct swirl patterns that will be visited by NASA's Lunar Vertex mission in 2024. We study the solar wind plasma interaction with Reiner Gamma for two lunar phases and IMF directions for a constant solar wind dynamic pressure using a hybrid plasma model (kinetic ions, fluid electrons). We analyze steady state outputs from the simulations in the ParaView visualization software and self-made Python scripts and present detailed maps of the plasma environment above Reiner Gamma from 10 km up to 100 km above the surface. From this, we show that a mini-magnetosphere forms from the interaction. Furthermore, we establish that the solar wind interaction with Reiner Gamma's crustal fields is affected by the lunar phase and IMF direction. The magnetic field intensity and the solar wind ion flux are shown to be largely influenced by the IMF direction, and the electric fields are affected by the lunar phase. Finally, we find that the strongest radial and tangential components of the electric fields are the electron inertial and hall terms.