Using Magnetohydrodynamics With Adaptively Embedded Particle-In-Cell (MHD-AEPIC) to Simulate Magnetic Island Coalescence

Simulating collisionless magnetic reconnection usually requires kinetic models that are computationally expensive in comparison with fluid approaches. In the present work, we study the magnetic island coalescence problem using the magnetohydrodynamics with adaptively embedded particle-in-cell (MHD-AEPIC) model, an innovative approach that embeds one or more adaptive particle-in-cell regions into a global MHD simulation domain such that the kinetic treatment is applied only in regions where kinetic physics is significant. We provide comparisons of simulation results among three different approaches: MHD with adaptively embedded PIC regions, MHD with statically embedded PIC regions, and a full PIC simulation. We analyze reconnection rates, magnetic island O-point separations, and the structures of the out-of-plane current densities, ion pressure tensor elements, and ion agyrotropy, yielding excellent agreement among all three approaches.