Scaling of magnetic reconnection in relativistic collisionless plasmas

TL;DR

This study uses kinetic simulations to analyze how the inflow speed of magnetic reconnection scales from non-relativistic to ultra-relativistic regimes, revealing that the reconnection rate increases with magnetization and approaches the speed of light.

Contribution

It provides a comprehensive model explaining the scaling of reconnection inflow speed across relativistic regimes, highlighting the role of Lorentz contraction and pressure tensor divergence.

Findings

Inflow speed approaches light speed at high magnetization

Reconnection rate is enhanced in relativistic regimes

Diffusion region aspect ratio remains ~0.1 across regimes

Abstract

Using fully kinetic simulations, we study the scaling of the inflow speed of collisionless magnetic reconnection from the non-relativistic to ultra-relativistic limit. In the anti-parallel configuration, the inflow speed increases with the upstream magnetization parameter $\sigma$ and approaches the light speed when $\sigma > O(100)$, leading to an enhanced reconnection rate. In all regimes, the divergence of pressure tensor is the dominant term responsible for breaking the frozen-in condition at the x-line. The observed scaling agrees well with a simple model that accounts for the Lorentz contraction of the plasma passing through the diffusion region. The results demonstrate that the aspect ratio of the diffusion region remains $\sim 0.1$ in both the non-relativistic and relativistic limits.