Fast Shocks From Magnetic Reconnection Outflows

TL;DR

This paper demonstrates through simulations that magnetic reconnection outflows can produce weak fast shocks, which may significantly contribute to particle acceleration in solar and astrophysical environments.

Contribution

It provides the first direct numerical evidence that reconnection outflows generate weak fast shocks capable of accelerating particles, expanding understanding of acceleration mechanisms.

Findings

Reconnection outflows produce weak fast shocks under certain conditions.

These shocks lead to a steep Fermi acceleration particle spectrum.

The mechanism is likely common in various astrophysical reconnection environments.

Abstract

Magnetic reconnection is commonly perceived to drive flow and particle acceleration in flares of solar, stellar, and astrophysical disk coronae but the relative roles of different acceleration mecha- nisms in a given reconnection environment are not well understood. We show via direct numerical simulations that reconnection outflows produce weak fast shocks, when conditions for fast recon- nection are met and the outflows encounter an obstacle. The associated compression ratios lead to a Fermi acceleration particle spectrum that is significantly steeper than the strong fast shocks commonly studied, but consistent with the demands of solar flares. While this is not the only acceleration mechanism operating in a reconnection environment, it is plausibly a ubiquitous one.