Foreshock-magnetosphere coupling at Mercury in a global hybrid (kinetic ion/fluid electron) model

Under typical solar wind conditions, there is a significant radial component of the interplanetary magnetic field at Mercury. This favors the generation of a quasi-parallel bow shock on the day side of Mercury. We explore the resulting foreshock waves driven by reflected ions streaming back towards the Sun and how the waves couple to Mercury’s magnetosphere. Because the magnetosheath behind Mercury’s bowshock is only ~10-20 ion skin depths wide, the foreshock readily couples to Flux Transfer Events at the subsolar magnetopause and generates large-amplitude fluctuations that enter the polar cusp regions. We compare global three-dimensional global hybrid (kinetic ion/fluid electron) simulations at realistic scale using the Hybrid-VPIC code [1] to data from MESSENGER spacecraft flybys. [1] Le et al. "Hybrid-VPIC: An open-source kinetic/fluid hybrid particle-in-cell code." Physics of Plasmas 30.6 (2023).