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Density jump for parallel and perpendicular collisionless shocks

Published online by Cambridge University Press:  14 April 2020

Antoine Bret*
Affiliation:
ETSI Industriales, Universidad de Castilla-La Mancha, 13071Ciudad Real, Spain Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071Ciudad Real, Spain
Ramesh Narayan
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA02138, USA
*
Author for correspondence: Antoine Bret, Universidad de Castilla-La Mancha, ETSI INDUSTRIALES, Avda Camilo José Cela s/n, 13071Ciudad Real, Spain. E-mail: [email protected]

Abstract

In a collisionless shock, there are no binary collisions to isotropize the flow. It is therefore reasonable to ask to which extent the magnetohydrodynamics (MHD) jump conditions apply. Following up on recent works which found a significant departure from MHD in the case of parallel collisionless shocks, we here present a model allowing to compute the density jump for collisionless shocks. Because the departure from MHD eventually stems from a sustained downstream anisotropy that the Vlasov equation alone cannot specify, we hypothesize a kinetic history for the plasma, as it crosses the shock front. For simplicity, we deal with non-relativistic pair plasmas. We treat the cases of parallel and perpendicular shocks. Non-MHD behavior is more pronounced for the parallel case where, according to MHD, the field should not affect the shock at all.

Type
Research Article
Copyright
Copyright © The Author(s), 2020. Published by Cambridge University Press

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