MHD-AEPIC: Coupled MHD-kinetic simulation of global, meso-, and small-scale magnetospheric phenomena

To capture physics in global, meso, and kinetic-scales, the Magnetohydrodynamics with Adaptively Embedded Particle-In-Cell (MHD-AEPIC) model couples the FLexible Exascale Kinetic Simulator (FLEKS) particle-in-cell (PIC) code with the Space Weather Modeling Framework (SWMF) global MHD simulation of Earth’s magnetosphere. This powerful code saves computational cost over global kinetic simulations via a flexible coupling, allowing the kinetic code to be activated in customizable smaller regions below the global scale as well as adapt the spatial coverage of the kinetic region at runtime. In this presentation, we summarize ongoing work and recent model capabilities in various physics domains. Specifically, MHD-AEPIC has been used to simulate magnetotail reconnection for multiple extreme geomagnetic storm events, showing global impacts of kinetic physics far downtail. The PIC region has also been placed over the dayside magnetopause to study reconnection onset and x-line topology, with the kinetic physics producing multiple highly-dynamic x-lines that can extend past the terminator in local time even under idealized conditions. Configured to cover the dayside solar wind-magnetosphere coupling, the MHD-AEPIC simulation can also produce the ion and electron foreshocks that have been the focus of earlier large-scale kinetic simulations. Finally, we highlight the unique capabilities of MHD-AEPIC to produce particle distributions and differential fluxes analogous to observations by magnetospheric missions such as MMS. The simulated distributions can be extracted from any location in the kinetic code, and the individual particles can be traced backward and forward in time to identify source and loss regions. Unlike test particle simulations, the particles in MHD-AEPIC control the plasma state variables of the simulation, which allows us to examine self-consistent mesoscale features such as bursty bulk flows and their evolving distribution functions. With these capabilities, the MHD-AEPIC model represents a major step forward in realistic magnetospheric simulations that can be carried out with current computational resources over time scales of a geomagnetic storm.