Particle acceleration in fragmenting periodic reconnecting current sheets in solar flares

Abstract

Proton and electron acceleration in a fragmenting periodic current sheet (CS) is investigated, based on the forced magnetic reconnection scenario. The aim is to understand the role of CS fragmentation in high-energy beam generation in solar flares. We combine magnetohydrodynamics and test-particle models to consider particle trajectories consistent with a time-dependent reconnection model. It is shown that accelerated particles in such a model form two distinct populations. Protons and electrons moving in open magnetic field have energy spectra that are a combination of the initial Maxwellian distribution and a power-law high-energy (E > 20 keV) part. The second population contains particles moving in a closed magnetic field around O-points. These particles move predominantly along the guiding field and their energies fall within quite a narrow range between ∼1 MeV and ∼10 MeV. It is also found that particles moving in an open magnetic field have a considerably wider pitch-angle distribution. © 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.