Simultaneous Proton and Electron Energization during Macroscale Magnetic Reconnection

TL;DR

This study uses simulations to show that magnetic reconnection accelerates electrons and protons into powerlaw energy distributions, with protons gaining more energy and extending to higher energies than electrons, influenced by magnetic field configurations.

Contribution

It demonstrates the simultaneous energization of electrons and protons in macroscale magnetic reconnection and highlights the role of Fermi reflection and guide fields in particle acceleration.

Findings

Both species form extended powerlaw distributions over three decades in energy.

Protons gain more energy and extend to higher energies than electrons.

A strong guide field reduces non-thermal particle production.

Abstract

The results of simulations of magnetic reconnection accompanied by electron and proton heating and energization in a macroscale system are presented. Both species form extended powerlaw distributions that extend nearly three decades in energy. The primary drive mechanism for the production of these nonthermal particles is Fermi reflection within evolving and coalescing magnetic flux ropes. While the powerlaw indices of the two species are comparable, the protons overall gain more energy than electrons and their power law extends to higher energy. The power laws roll into a hot thermal distribution at low energy with the transition energy occurring at lower energy for electrons compared with protons. A strong guide field diminishes the production of non-thermal particles by reducing the Fermi drive mechanism. In solar flares, proton power laws should extend down to 10's of keV, far below the energies that can be directly probed via gamma-ray emission. Thus, protons should carry much more of the released magnetic energy than expected from direct observations.