Global Magnetospheric Model with Microscopic Physics: MHD-EPIC

In the last 5 years we have developed and implemented the magnetohydrodynamics with embedded particle-in-cell (MHD-EPIC) model. MHD-EPIC allows performing global MHD simulations two-way coupled with local PIC simulations covering one or more regions where kinetic effects are important, such as magnetic reconnection sites. We have improved the PIC algorithm to conserve energy and satisfy Gauss' law at the same time, generalized the MHD-PIC coupling to arbitrary MHD grids and rotated PIC regions, and improved the efficiency of the coupler. We have also studied the technique of artificially increasing the kinetic scales by changing the mass per charge ratio for the ions and electrons, and we found that the global solution remains essentially the same as long as the global and kinetic scales are reasonably well separated.

The combination of these new technologies and insights enabled us to perform MHD-EPIC simulations for several magnetospheres, including Ganymede, Mercury, Mars, Earth and Saturn. In this talk we will demonstrate these capabilities for modeling Earth's magnetosphere with the PIC region covering the dayside or tail reconnection sites. On the dayside we compare the model with observations of flux transfer events and kinetic scale observations by the MMS space craft. For the magnetotail we study the dynamics of the reconnection process that appears to reproduce several features of sawtooth events for strong but steady driving with negative Bz field. Our work is supported by the NSF INSPIRE and PRE-EVENTS grants.