Scaling of asymmetric magnetic reconnection: Kinetic particle-in-cell simulations

Recently, Cassak and Shay (2007) applied a generalized Sweet-Parker analysis to derive scaling laws for gross properties of asymmetric magnetic reconnection, including the reconnection rate, outflow speed, and outflow density. This study presents the first comprehensive test of this scaling theory using fully electromagnetic particle-in-cell simulations of antiparallel asymmetric magnetic reconnection. By varying the upstream densities and magnetic fields, we find that the reconnection rates, outflow speeds, and outflow densities are consistent with the general scaling theory. This implies that kinetic electron and proton physics beyond the Hall term does not fundamentally alter the gross properties of the asymmetric diffusion region as understood in Cassak and Shay (2007). In addition, the results confirm the validity of the assumption of mixing of particles on recently reconnected flux tubes, which is of key importance for accurately predicting the location of the flow stagnation point in the diffusion region.