How Anomalous Resistivity Accelerates Magnetic Reconnection

TL;DR

This paper demonstrates through particle-in-cell simulations that anomalous resistivity caused by Buneman instability can significantly accelerate magnetic reconnection by enhancing energy dissipation and electric fields at electron scales.

Contribution

It provides the first detailed simulation evidence that anomalous resistivity from Buneman instability can facilitate fast magnetic reconnection in collisionless plasma.

Findings

AR dissipates magnetic energy via electron beam kinetic energy

Impulsive fast reconnection occurs with a rate up to 0.6 V_A

Approximately 40% of magnetic energy converts to electron thermal energy

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 0.6 $V_A$. 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 enhances the reconnection electric field and the in-plane perpendicular magnetic field. About 40\% of the released magnetic energy is converted into the electron thermal energy by AR while 50\% is converted into the 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.