Acceleration of cold ions in magnetic reconnection

Abstract

This paper describes the results of 2.5D particle-in-cell kinetic simulations of magnetic reconnection. We consider the case without cold ions (case 0) and with a cold ion flow loaded at two localized positions (cases 1 and 2). The cold ions are loaded on the lower side of the inflow region in cases 1 and 2: along the x-direction, the cold ions are centered at the x location of the X-line in case 1 and are positioned to one side in case 2. Our simulations suggest that cold ions are accelerated and heated near the upper separatrix region in both cases 1 and 2. The gyroradius of the orbit of cold ions increases in the diffusion region owing to the weak magnetic field and then enter the outflow region, where the cold ions pick up the E×B outflow. The cold ions are prevented from crossing the upper separatrix by the Hall electric field, which is negative at the upper exhaust region separatrix. The cold ions are accelerated along the negative z-direction in the upper inflow region by the nonideal electric field (E+vci×B)z for case 1. During this process, the cold ions undergo demagnetization drift association with the finite Larmor radius effect of cold ions. Yet, the reconnection rate decreases after the cold ions flow into the diffusion region. However, the magnetic reconnection rate exhibits no significant changes in case 2.