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Proton temperature-anisotropy-driven instabilities in weakly collisional plasmas: Hybrid simulations

Published online by Cambridge University Press:  28 August 2014

Petr Hellinger*
Affiliation:
Astronomical Institute AS CR, Bocni II/1401, CZ-14131 Prague, Czech Republic Institute of Atmospheric Physics, AS CR, Bocni II/1401, CZ-14131 Prague, Czech Republic
Pavel M. Trávníček
Affiliation:
Astronomical Institute AS CR, Bocni II/1401, CZ-14131 Prague, Czech Republic Institute of Atmospheric Physics, AS CR, Bocni II/1401, CZ-14131 Prague, Czech Republic Space Sciences Laboratory, UCB, Berkeley, USA
*
Email address for correspondence: Petr.Hellinger@asu.cas.cz

Abstract

Kinetic instabilities in weakly collisional, high beta plasmas are investigated using two-dimensional hybrid expanding box simulations with Coulomb collisions modeled through the Langevin equation (corresponding to the Fokker-Planck one). The expansion drives a parallel or perpendicular temperature anisotropy (depending on the orientation of the ambient magnetic field). For the chosen parameters the Coulomb collisions are important with respect to the driver but are not strong enough to keep the system stable with respect to instabilities driven by the proton temperature anisotropy. In the case of the parallel temperature anisotropy the dominant oblique fire hose instability efficiently reduces the anisotropy in a quasilinear manner. In the case of the perpendicular temperature anisotropy the dominant mirror instability generates coherent compressive structures which scatter protons and reduce the temperature anisotropy. For both the cases the instabilities generate temporarily enough wave energy so that the corresponding (anomalous) transport coefficients dominate over the collisional ones and their properties are similar to those in collisionless plasmas.

Information

Type
Research Article
Copyright
Copyright © Cambridge University Press 2014 

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