2015/05/31 by Xiaocan Li, Fan Guo, Hui Li +1 · 1 citation
Physics and Astronomy · #astro-ph.SR #astro-ph.HE #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.1088/2041-8205/811/2/l24
published as The Astrophysical Journal Letters, 811:L24, 2015 · 5 pages, 3 figures, accepted by ApJ Letters
arxiv created 2015/09/25 · arxiv updated 2015/09/29
By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton--electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization. We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. The nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the highly efficient electron acceleration in solar flares and other astrophysical systems.