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Title: Particle Acceleration and Fractional Transport in Turbulent Reconnection

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 analysismore » 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.« less

Authors:
; ;  [1];  [2]
  1. Department of Physics, Aristotle University of Thessaloniki, GR-52124 Thessaloniki (Greece)
  2. Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, GR-15236 Penteli (Greece)
Publication Date:
OSTI Identifier:
22679716
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 849; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 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

Citation Formats

Isliker, Heinz, Pisokas, Theophilos, Vlahos, Loukas, and Anastasiadis, Anastasios. Particle Acceleration and Fractional Transport in Turbulent Reconnection. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8EE8.
Isliker, Heinz, Pisokas, Theophilos, Vlahos, Loukas, & Anastasiadis, Anastasios. Particle Acceleration and Fractional Transport in Turbulent Reconnection. United States. doi:10.3847/1538-4357/AA8EE8.
Isliker, Heinz, Pisokas, Theophilos, Vlahos, Loukas, and Anastasiadis, Anastasios. Wed . "Particle Acceleration and Fractional Transport in Turbulent Reconnection". United States. doi:10.3847/1538-4357/AA8EE8.
@article{osti_22679716,
title = {Particle Acceleration and Fractional Transport in Turbulent Reconnection},
author = {Isliker, Heinz and Pisokas, Theophilos and Vlahos, Loukas and Anastasiadis, Anastasios},
abstractNote = {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.},
doi = {10.3847/1538-4357/AA8EE8},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 849,
place = {United States},
year = {2017},
month = {11}
}