Particle Acceleration in Turbulence and Weakly Stochastic Reconnection

Type Journal Article
Names Grzegorz Kowal, Elisabete M. de Gouveia Dal Pino, A. Lazarian
Publication Physical Review Letters
Volume 108
Issue 24
Pages 241102
Date June 1, 2012
DOI DOI: 10.1103/PhysRevLett.108.241102; eprintid: arXiv:1202.5256
Library Catalog NASA ADS
Abstract In this Letter we analyze the energy distribution evolution of test particles injected in three dimensional (3D) magnetohydrodynamic (MHD) simulations of different magnetic reconnection configurations. When considering a single Sweet-Parker topology, the particles accelerate predominantly through a first-order Fermi process, as predicted in and demonstrated numerically in . When turbulence is included within the current sheet, the acceleration rate is highly enhanced, because reconnection becomes fast and independent of resistivity and allows the formation of a thick volume filled with multiple simultaneously reconnecting magnetic fluxes. Charged particles trapped within this volume suffer several head-on scatterings with the contracting magnetic fluctuations, which significantly increase the acceleration rate and results in a first-order Fermi process. For comparison, we also tested acceleration in MHD turbulence, where particles suffer collisions with approaching and receding magnetic irregularities, resulting in a reduced acceleration rate. We argue that the dominant acceleration mechanism approaches a second order Fermi process in this case.
Tags COSMIC RAYS, Magnetic reconnection
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