Two dimensional magnetic merging and reconnection

Abstract

Magnetic energy release is mergin flows in investigated by numerical integration of unsteady resistive MHD equations in two dimensions. No explosive magnetic energy release is found in two topologically distinct merging flow geometries, in the absence of imposed strong plasma inflows. The first geometry is the merging of straight field lines without magnetic reconnection, and the second is merging with reconnection at an x-type neutral point. In each geometry the merging energy release is compared with the diffusive energy release in the absence of plasma motion. It is found in both geometries that the merging energy release is less than the diffusive energy release. Magnetic island formation occurs in the reconnection simulation. The magnetic energy release appears mainly as thermal rather than kinetic energy, but the heating is not localized. These results indicate that two dimensional merging without strong forcing is not promising as a mechanism for explosive magnetic energy release, but is more promising for gradual plasma heating and magnetic field dissipation. It is suggested that similar results would apply to any merging geometry which is stable in ideal MHD.