Whether Turbulence-induced anomalous resistivity (AR) can facilitate a fast magnetic reconnection in collisionless plasma is a subject of active debate for decades. A particularly difficult problem in experimental and numerical simulation studies of the problem is how to distinguish the effects of AR from those originating from Hall-effect and other non-turbulent processes in the generalized Ohm’s. 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 in a thin current layer, the AR produced by Buneman instability spontaneously breaks the magnetic field lines and causes impulsive fast non-Hall magnetic line annihilation on electron-scales with a rate reaching 0.6~$V_A$. However, the electron-scale magnetic line annihilation is not a necessary condition for the dissipation of magnetic energy, but rather a result of the inhomogeneity of the AR. On the other hand, the inhomogeneous drag arising from a Buneman instability driven by the intense electron beams at the x-line in a 3D magnetic reconnection can drive in the electron diffusion region electron-scale magnetic line annihilation. The electron-scale annihilations play an essential role in accelerating the magnetic reconnection with a rate two times faster than the non-turbulent Hall-dominated 2D magnetic reconnection. The reconnection rate is enhanced around the x-line, and the coupling between the AR carried out by the reconnection outflow and the Hall effect leads to the breaking of the symmetric structure of the ion diffusion region and the enhancement of the outward Poynting flux.
Tue, 21 Feb 17
Comments: submitted to Physics of Plasma