Particle Dynamics at the Earth's Bow Shock: PIC simulations and MMS observations

Abstract:

A global Particle-in-cell (PIC) simulation code has been used to study the interaction of the solar wind and Earth's magnetosphere. A bow shock can be generated self-consistently ahead of the magnetosphere after tens of ion gyroperiods. We find that (1) the shock front can be nonstationary and self-reforming in high Mach number and low plasma beta solar wind conditions (Self-reformation: a physical phenomenon which describes a fraction of solar wind incident ions are reflected at the shock, and then they are accumulated ahead of the old shock front. Such reflected ions can generate a new shock front after 1-2 ion gyroperiods and the old shock front becomes blurred. Finally, the new shock front start to reflect new incident solar wind ions. Such a periodic process is called self-reformation of the shock front), (2) Asymmetric magnetopause and Harris current sheet magnetotail reconnections are also retrieved in our global PIC simulations. These reconnection phenomena have been directly observed by MMS and Cluster very open. In contrast to local PIC simulations, we use nature boundary conditions for such reconnection regions because of the global setups of the simulation model, and (3) MMS mission give us an opportunity to directly observe the self-reforming nonstationary bow shock and to trace the particle behavior in a relatively high resolution. 3D velocity distributions observed by MMS from upstream to downstream during a quasi-perpendicular bow shock crossing has been fully compared with the simulation result issued from a three-dimensional PIC simulation with inputs from MMS satellite data.