Nonlinear Explosive Magnetic Reconnection in a Collisionless System

TL;DR

This paper demonstrates through high-resolution simulations that explosive magnetic reconnection can occur in collisionless plasmas with thick current sheets, driven by enhanced inertia resistivity and particle magnetization, with rapid energy dissipation.

Contribution

It reveals a new mechanism for fast magnetic reconnection in thick current sheets, expanding understanding beyond the thin-sheet paradigm in collisionless plasma systems.

Findings

Explosive reconnection occurs regardless of initial current sheet thickness.

Enhanced inertia resistivity due to particle magnetization drives rapid reconnection.

The nonlinear reconnection timescale is on the order of tens of Alfvén transit times.

Abstract

The debate surrounding fast magnetic energy dissipation by magnetic reconnection has remained a fundamental topic in the plasma universe, not only in the Earth's magnetosphere but in astrophysical objects such as pulsar magnetospheres and magnetars, for more than half a century. Recently, nonthermal particle acceleration and plasma heating during reconnection have been extensively studied, and it has been argued that rapid energy dissipation can occur for a collisionless "thin" current sheet, the thickness of which is of the order of the particle gyro-radius. However, it is an intriguing enigma as to how the fast energy dissipation can occur for a "thick" current sheet with thickness larger than the particle gyro-radius. Here we demonstrate, using a high-resolution particle-in-cell simulation for a pair plasma, that an explosive reconnection can emerge with the enhancement of the inertia resistivity due to the magnetization of the meandering particles by the reconnecting magnetic field and the shrinkage of the current sheet. In addition, regardless of the initial thickness of the current sheet, the time scale of the nonlinear explosive reconnection is tens of the Alfv\'{e}n transit time.