Multi-Hierarchy Simulation of Collisionless Driven Reconnection by Real-Space Decomposition

The first results on analysis of collisionless driven reconnection with a multihierarchy simulation model are reported. In the multi-hierarchy simulation model, real space in a simulation consists of three parts: a magnetohydrodynamics (MHD) domain to deal with macroscopic dynamics, a particle-in-cell (PIC) domain to solve microscopic kinetic physics from the first principle, and an interface domain to interlock the two domains. By means of multi-hierarchy simulations, the influence of macroscopic dynamics on microscopic physics of magnetic reconnection is investigated. Dynamical behaviors of collisionless reconnection in the PIC domain depend strongly on plasma inflows from the MHD domain. It is found that if the width of an MHD inflow increases as v_w ≲ v_A0, where v_A0 is the Alfvén speed at the upstream boundary, magnetic reconnection has only a single X-point., while in cases of v_w≳2.0v_A0, reconnection with multiple X-points takes place.