Interaction of Interplanetary Shocks With the Moon: Hybrid Simulations and ARTEMIS Observations

Abstract

AbstractWhen in the solar wind, the Moon is exposed to its embedded discontinuities such as interplanetary (IP) shocks. In this study we utilize 3‐D electromagnetic hybrid (kinetic ions, fluid electrons) simulations and observations of two events, by THEMIS/ARTEMIS spacecraft to understand the interaction of IP shocks with the Moon. Simulation parameters are based on one of the ARTEMIS events and include the presence of supra‐thermal ions in the solar wind. The results show that the absorption of the cold solar wind protons on the Moon's dayside leads to a density hole in the shock front behind the Moon. This density hole refills and recovers as the IP shock moves down the lunar tail. Penetration of the interplanetary magnetic field through Moon's body leads to the survival of a steepened magnetic structure associated with the shock surface. However, due to the lower pressures in the lunar tail the structure broadens in space and is expected to steepen when the IP shock is beyond the tail. The IP shock is also found to interact with the energetic ions in the lunar tail resulting in their acceleration to higher energies. Comparing the densities measured by ARTEMIS in the solar wind and lunar tail shows the absence of a shock front in density in the tail consistent with the formation of a density hole at the shock front. Similarly, comparing the magnetic field profiles in the solar wind and lunar tail shows the expected broadening of the magnetic field shock front.