How anomalous resistivity accelerates magnetic reconnection

Abstract

Whether turbulence induced anomalous resistivity (AR) can facilitate a fast magnetic reconnection in collisionless plasma is a subject of active debate for decades. Recent space observations suggest that the reconnection rate can be higher than the Hall-reconnection rate and turbulent dissipation is required. In this paper, using particle-in-cell simulations, we present a case study of how AR produced by Buneman instability accelerates magnetic reconnection. We first show that the AR/drag produced by Buneman instability in a thin electron current layer (1) can dissipate magnetic energy stored in the current layer through dissipation of the kinetic energy of electron beams; (2) the inhomogeneous drag caused by wave couplings spontaneously breaks the magnetic field lines and causes impulsive fast non-Hall magnetic reconnection on electron-scales with a mean rate reaching of 0.6 VA. We then show that a Buneman instability driven by intense electron beams around the x-point in a 3D magnetic reconnection significantly enhances the dissipation of the magnetic energy. Electron-scale magnetic reconnections driven by the inhomogeneous drag around the x-line enhance the reconnection electric field and the in-plane perpendicular magnetic field. About 40% of the released magnetic energy is converted into electron thermal energy by AR while 50% is converted into kinetic energy of the electron beams through the acceleration by the reconnection electric field. The enhanced magnetic energy dissipation is balanced by a net Poynting flux in-flow. About 10% of the released magnetic energy is brought out by an enhanced Poynting flux out-flow. These results suggest that AR with sufficient intensity and electron-scale inhomogeneity can significantly accelerate magnetic reconnection.