Cosmic Ray Acceleration in Magnetic Reconnection Sites

TL;DR

This paper reviews how magnetic reconnection sites can efficiently accelerate cosmic rays through a first-order Fermi process, supported by 3D MHD simulations showing energy spectrum evolution.

Contribution

It presents new 3D collisional MHD simulations demonstrating efficient cosmic ray acceleration in magnetic reconnection regions, highlighting the role of turbulence.

Findings

Cosmic rays can be accelerated efficiently in reconnection sites.

Turbulence enhances the reconnection speed and acceleration layer thickness.

Simulations show a significant energy spectrum evolution indicating effective acceleration.

Abstract

Cosmic Ray (CR) acceleration still challenges the researchers. Fast particles may be accelerated in astrophysical environments by a variety of processes. Acceleration in magnetic reconnection sites in particular, has lately attracted the attention of researchers not only for its potential importance in the solar system context, but also in other astrophysical environments, like compact stellar sources, AGNs and GRBs, and even in diffusive media like the ISM and the IGM, especially when the environment is magnetically dominated. In this talk we review this process and also present three-dimensional collisional MHD simulations with the injection of thousands of test particles showing from the evolution of their energy spectrum that they can be efficiently accelerated by reconnection through a first-order Fermi process within large scale magnetic current sheets (especially when local turbulence is present which makes reconnection fast and the acceleration layer thicker).