Gyro-induced acceleration of magnetic reconnection

TL;DR

This paper investigates the linear and nonlinear phases of magnetic reconnection in collisionless plasmas, revealing acceleration phases driven by ion gyration and temperature effects, with reconnection rates reaching a constant maximum.

Contribution

It provides a detailed analysis of the acceleration mechanisms in magnetic reconnection using a gyrofluid model, highlighting the role of ion and electron temperature effects.

Findings

Two acceleration phases in nonlinear reconnection evolution.

Maximum growth rate increases dramatically over linear value.

Reconnection rate asymptotes to a constant at small diffusion layers.

Abstract

The linear and nonlinear evolution of magnetic reconnection in collisionless high-temperature plasmas with a strong guide field is analyzed on the basis of a two-dimensional gyrofluid model. The linear growth rate of the reconnecting instability is compared to analytical calculations over the whole spectrum of linearly unstable wave numbers. In the strongly unstable regime (large \Delta '), the nonlinear evolution of the reconnecting instability is found to undergo two distinctive acceleration phases separated by a stall phase in which the instantaneous growth rate decreases. The first acceleration phase is caused by the formation of strong electric fields close to the X-point due to ion gyration, while the second acceleration phase is driven by the development of an open Petschek-like configuration due to both ion and electron temperature effects. Furthermore, the maximum instantaneous growth rate is found to increase dramatically over its linear value for decreasing diffusion layers. This is a consequence of the fact that the peak instantaneous growth rate becomes weakly dependent on the microscopic plasma parameters if the diffusion region thickness is sufficiently smaller than the equilibrium magnetic field scale length. When this condition is satisfied, the peak reconnection rate asymptotes to a constant value.