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Author Isliker, Heinz ♦ Pisokas, Theophilos ♦ Vlahos, Loukas ♦ Anastasiadis, Anastasios
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ ACCELERATION ♦ DIFFUSION ♦ DISTRIBUTION ♦ ELECTRIC FIELDS ♦ ELECTRONS ♦ ENERGY SPECTRA ♦ FOKKER-PLANCK EQUATION ♦ MAGNETIC RECONNECTION ♦ PARTICLES ♦ PLASMA ♦ RANDOMNESS ♦ REFLECTION ♦ SIMULATION ♦ SPACE ♦ TRANSPORT THEORY ♦ TURBULENCE
Abstract We consider a large-scale environment of turbulent reconnection that is fragmented into a number of randomly distributed unstable current sheets (UCSs), and we statistically analyze the acceleration of particles within this environment. We address two important cases of acceleration mechanisms when particles interact with the UCS: (a) electric field acceleration and (b) acceleration by reflection at contracting islands. Electrons and ions are accelerated very efficiently, attaining an energy distribution of power-law shape with an index 1–2, depending on the acceleration mechanism. The transport coefficients in energy space are estimated from test-particle simulation data, and we show that the classical Fokker–Planck (FP) equation fails to reproduce the simulation results when the transport coefficients are inserted into it and it is solved numerically. The cause for this failure is that the particles perform Levy flights in energy space, while the distributions of the energy increments exhibit power-law tails. We then use the fractional transport equation (FTE) derived by Isliker et al., whose parameters and the order of the fractional derivatives are inferred from the simulation data, and solving the FTE numerically, we show that the FTE successfully reproduces the kinetic energy distribution of the test particles. We discuss in detail the analysis of the simulation data and the criteria that allow one to judge the appropriateness of either an FTE or a classical FP equation as a transport model.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-11-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 849
Issue Number 1


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