The Heliophysics seminars are intended to allow guests and local members of the plasma physics community to present heliophysics related research and foster collaborations; to facilitate development of theoretical tools for understanding fundamental physical processes such as reconnection, turbulence, waves, and transport that control the dynamics in the context of the heliosphere; and to provide a forum to facilitate cross-fertilization between laboratory plasma physics, astrophysics, and heliospheric science.
It is challenging to capture kinetic phenomena in global simulations due to the significant difference between the kinetic scales and global scales. The magnetohydrodynamics with embedded particle-in-cell model (MHD-EPIC) is developed to incorporate kinetic physics into global simulations. It combines the physics capability of a particle-in-cell (PIC) code and the efficiency of an MHD model by coupling a semi-implicit PIC code with the global MHD model BATS-R-US. The PIC code is used to cover the regions where kinetic effects are important and the MHD model handles the rest part of the simulation domain.
We have improved the robustness of the PIC code by introducing the Gauss’s Law satisfying Energy Conserving Semi-Implicit Method (GL-ECSIM), which conserves energy and satisfies Gauss’s law numerically. Instead of modifying the electric field to satisfy Gauss’s law like the classical methods, we invented a new alternative approach: correcting the particle positions to satisfy the restriction. The simulation results demonstrate that the GL-ECSIM algorithm is accurate and robust. The capability of the MHD-EPIC model is further improved by using a new PIC code, the FLexible Exascale Kinetic Simulator (FLEKS). FLEKS allows PIC simulation domains of any shape so that it is more flexible to choose PIC regions in MHD-EPIC simulations. We have also designed particle resampling algorithms to further improve the accuracy and efficiency of FLEKS.
The MHD-EPIC model has been successfully applied to simulate planetary magnetospheres. We will present the simulation results of Earth’s and Mercury’s magnetospheres. The PIC region covers the dayside magnetopause in the simulation of Earth’s magnetosphere, and we studied the evolution of flux transfer events (FTEs) and compared the simulation results with observations. The MHD-EPIC model has also been applied to study the dawn-dusk asymmetry of Mercury’s magnetotail dynamics. It shows the asymmetries of the current sheet thickness, plasma density, reconnection site and reconnection jets.
T. DeHass1 C. Prior2, A Yeates2
1 Tri Alpha Energy, Irvine Ca. 2 Durham University, United Kingdom