# Determining the Dominant Acceleration Mechanism during Relativistic Magnetic Reconnection in Large-scale Systems

## TL;DR

This paper shows that Fermi-type acceleration in large-scale electric fields is the main mechanism for particle energization during relativistic magnetic reconnection, simplifying modeling of astrophysical high-energy phenomena.

## Contribution

It provides the first comprehensive analysis combining kinetic simulations and theory to identify the dominant acceleration process in large-scale relativistic reconnection.

## Key findings

- Fermi acceleration dominates over direct electric field acceleration.
- Large-scale motional electric fields are key to particle energization.
- Modeling can focus on large-scale fields without resolving microscopic diffusion regions.

## Abstract

While a growing body of research indicates that relativistic magnetic reconnection is a prodigious source of particle acceleration in high-energy astrophysical systems, the dominant acceleration mechanism remains controversial. Using a combination of fully kinetic simulations and theoretical analysis, we demonstrate that Fermi-type acceleration within the large-scale motional electric fields dominates over direct acceleration from non-ideal electric fields within small-scale diffusion regions. This result has profound implications for modeling particle acceleration in large-scale astrophysical problems, since it opens up the possiblity of modeling the energetic spectra without resolving microscopic diffusion regions.