The Critical Role of Collisionless Plasma Energization on the Structure of Relativistic Magnetic Reconnection

TL;DR

This paper investigates how collisionless plasma energization influences the structure and dynamics of relativistic magnetic reconnection, revealing mechanisms behind the formation, stability, and bursty behavior of reconnection regions.

Contribution

It uncovers the critical role of plasma energization in shaping the reconnection diffusion region and explains how guide fields stabilize the process, advancing understanding of relativistic reconnection.

Findings

Pressure drops at the x-line cause collapse and localization of the diffusion region.

Bursty reconnection results from repeated collapse and secondary tearing.

Guide fields stabilize reconnection by providing additional magnetic pressure.

Abstract

During magnetically dominated relativistic reconnection, inflowing plasma depletes the initial relativistic pressure at the x-line and collisionless plasma heating inside the diffusion region is insufficient to overcome this loss. The resulting pressure drop causes a collapse at the x-line, essentially a localization mechanism of the diffusion region necessary for fast reconnection. The extension of this low-pressure region further explains the bursty nature of anti-parallel reconnection because a once opened outflow exhaust can also collapse, which repeatedly triggers secondary tearing islands. However, a stable single x-line reconnection can be achieved when an external guide field exists, since the reconnecting magnetic field component rotates out of the reconnection plane at outflows, providing additional magnetic pressure to sustain the opened exhausts.