Exact Calculation of Nonideal Fields Demonstrates Dominance of Injection in Relativistic Reconnection

TL;DR

This study uses exact calculations in kinetic simulations to show that nonideal electric fields dominate the initial particle energization in magnetic reconnection, especially in high-magnetization and 3D systems.

Contribution

It introduces a novel analysis method that conclusively demonstrates the dominance of nonideal fields in particle injection during reconnection, applicable across plasma physics.

Findings

Nonideal fields are the primary driver of early particle energization.

The importance of nonideal fields increases with magnetization and guide field.

The analysis method can be broadly applied to plasma physics processes.

Abstract

Magnetic reconnection is an important source of energetic particles in systems ranging from astrophysics to the laboratory. The large separation of spatiotemporal scales involved makes it critical to determine the minimum physical model containing the necessary physics for modeling particle acceleration. By resolving the energy gain from ideal and nonideal magnetohydrodynamic electric fields self-consistently in kinetic particle-in-cell simulations of reconnection, we conclusively show the dominant role of the nonideal field for the early stage of energization known as injection. The importance of the nonideal field increases with magnetization, guide field, and in three-dimensions, indicating its general importance for reconnection in natural astrophysical systems. We obtain the statistical properties of the injection process from the simulations, paving the way for the development of extended MHD models capable of accurately modeling particle acceleration in large-scale systems. The novel analysis method developed in this study can be applied broadly to give new insight into a wide range of processes in plasma physics.