The Role of the Guide Field in Relativistic Pair Plasma Reconnection

TL;DR

This paper investigates how the guide field influences relativistic magnetic reconnection in pair plasmas, revealing its role in stabilizing instabilities and enabling non-thermal particle acceleration through 3D simulations and theoretical analysis.

Contribution

It provides new insights into the stabilizing effect of the guide field on instabilities and the mechanisms of particle acceleration in relativistic reconnection.

Findings

Guide field stabilizes the relativistic drift-kink instability.

Secondary magnetic reconnection is triggered by oblique instabilities.

Guide field enables non-thermal particle acceleration in 3D reconnection.

Abstract

We study the role of the guide field in relativistic magnetic reconnection in a Harris current sheet of pair ($e^{\pm}$) plasmas, using linear theories and particle-in-cell (PIC) simulations. Two-dimensional PIC simulations exhibit the guide field dependence to the linear instabilities; the tearing or reconnection modes are relatively insensitive, while the relativistic drift-kink instability (RDKI), the fastest mode in a relativistic current sheet, is stabilized by the guide field. Particle acceleration in the nonlinear stage is also investigated. A three-dimensional PIC simulation demonstrates that the current sheet is unstable to the RDKI, although small reconnection occurs in the deformed current sheet. Another three-dimensional PIC simulation with a guide field demonstrates a completely different scenario. Secondary magnetic reconnection is triggered by nonlinear coupling of oblique instabilities, which we call the relativistic drift-sausage tearing instability. Therefore, particle acceleration by relativistic guide field reconnection occurs in three-dimensional configuration. Based on the plasma theories, we discuss an important role of the guide field: to enable non-thermal particle acceleration by magnetic reconnection.