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Particle trajectories in Weibel filaments: influence of external field obliquity and chaos

Part of: Focus on Plasma Astrophysics

Published online by Cambridge University Press:  27 May 2020

A. Bret Open the ORCID record for A. Bret [Opens in a new window]  and
M. E. Dieckmann Open the ORCID record for M. E. Dieckmann [Opens in a new window]
A. 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
M. E. Dieckmann
Affiliation:
Department of Science and Technology (ITN), Linköping University, 60174Norrköping, Sweden
*
†Email address for correspondence: antoineclaude.bret@uclm.es
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Abstract

When two collisionless plasma shells collide, they interpenetrate and the overlapping region may turn Weibel unstable for some values of the collision parameters. This instability grows magnetic filaments which, at saturation, have to block the incoming flow if a Weibel shock is to form. In a recent paper (Bret, J. Plasma Phys., vol. 82, 2016b, 905820403), it was found by implementing a toy model for the incoming particle trajectories in the filaments, that a strong enough external magnetic field $\unicode[STIX]{x1D63D}_{0}$ can prevent the filaments blocking the flow if it is aligned with them. Denoting by $B_{f}$ the peak value of the field in the magnetic filaments, all test particles stream through them if $\unicode[STIX]{x1D6FC}=B_{0}/B_{f}>1/2$. Here, this result is extended to the case of an oblique external field $B_{0}$ making an angle $\unicode[STIX]{x1D703}$ with the flow. The result, numerically found, is simply $\unicode[STIX]{x1D6FC}>\unicode[STIX]{x1D705}(\unicode[STIX]{x1D703})/\cos \unicode[STIX]{x1D703}$, where $\unicode[STIX]{x1D705}(\unicode[STIX]{x1D703})$ is of order unity. Noteworthily, test particles exhibit chaotic trajectories.

Keywords

astrophysical plasmasplasma flowsplasma nonlinear phenomena
Type
Research Article
Information
Journal of Plasma Physics , Volume 86 , Issue 3 , June 2020 , 905860305
Copyright
© Cambridge University Press 2020

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