First order Fermi acceleration driven by magnetic reconnection

TL;DR

This paper uses a simple box model to analyze how magnetic reconnection can drive first order Fermi acceleration, revealing that the spectral index depends on compression and differs from the universal E^{-5/2} spectrum.

Contribution

It demonstrates that the spectral index in magnetic reconnection-driven acceleration depends on compression, challenging the idea of a universal spectrum, and estimates the acceleration time-scale.

Findings

Spectral index relates to total compression, similar to shock acceleration.

The spectrum is not universally E^{-5/2}.

Estimated acceleration time-scale.

Abstract

A box model is used to study first order Fermi acceleration driven by magnetic reconnection. It is shown, at least in this simple model, that the spectral index of the accelerated particles is related to the total compression in the same way as in diffusive shock acceleration and is not, as has been suggested, a universal $E^{-5/2}$ spectrum. The acceleration time-scale is estimated and some comments made about the applicability of the process.