The Weibel Instability inside the Electron-Positron Harris Sheet

TL;DR

This paper investigates the Weibel instability within electron-positron current sheets during reconnection, combining theoretical modeling, numerical solutions, and particle simulations to understand its role in current layer dynamics.

Contribution

A four-beam model is developed to analyze the Weibel instability in narrow reconnection layers, validated by simulations, revealing its impact on current layer broadening.

Findings

The linear theory matches particle simulation results.

The Weibel instability causes current layer broadening.

High-velocity particles are scattered by Weibel-generated magnetic fields.

Abstract

Recent full-particle simulations of electron-positron reconnection have revealed that the Weibel instability plays an active role in controlling the dynamics of the current layer and maintaining fast reconnection. A four-beam model is developed to explore the development of the instability within a narrow current layer characteristic of reconnection. The problem is reduced to two coupled second-order differential equations, whose growing eigenmodes are obtained via both asymptotic approximations and finite difference methods. Full particle simulations confirm the linear theory and help probe the nonlinear development of the instability. The current layer broadening in the reconnection outflow jet is linked to the scattering of high-velocity streaming particles in the Weibel-generated, out-of-plane magnetic field.