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Microstructure in two-and three-dimensional hybrid simulations of perpendicular collisionless shocks

Microstructure in two-and three-dimensional hybrid simulations of perpendicular collisionless shocks
Microstructure in two-and three-dimensional hybrid simulations of perpendicular collisionless shocks

Supercritical collisionless perpendicular shocks have an average macrostructure determined primarily by the dynamics of ions specularly reflected at the magnetic ramp. Within the overall macrostructure, instabilities, both linear and nonlinear, generate fluctuations and microstructure. To identify the sources of such microstructure, high-resolution two-and three-dimensional simulations have been carried out using the hybrid method, wherein the ions are treated as particles and the electron response is modelled as a massless fluid. We confirm the results of earlier two-dimensional (2-D) simulations showing both field-parallel aligned propagating fluctuations and fluctuations carried by the reflected-gyrating ions. In addition, it is shown that, for 2-D simulations of the shock coplanarity plane, the presence of short-wavelength fluctuations in all magnetic components is associated with the ion Weibel instability driven at the upstream edge of the foot by the reflected-gyrating ions. In 3-D simulations we show for the first time that the dominant microstructure is due to a coupling between field-parallel propagating fluctuations in the ramp and the motion of the reflected ions. This results in a pattern of fluctuations counter-propagating across the surface of the shock at an angle inclined to the magnetic field direction, due to a combination of field-parallel motion at the Alfvén speed of the ramp and motion in the sense of gyration of the reflected ions.

0022-3778
1-23
Burgess, David
9d9bae4d-ccf5-4ead-bebb-67177cd8603e
Hellinger, Petr
58e1e3df-d91a-4524-b27b-3c75a5bbed5e
Gingell, Imogen
ba7b8113-3833-40d8-a879-aab3f987455d
Trávníček, Pavel M.
4aa55b9c-8f97-47c7-9361-e7843f404651
Burgess, David
9d9bae4d-ccf5-4ead-bebb-67177cd8603e
Hellinger, Petr
58e1e3df-d91a-4524-b27b-3c75a5bbed5e
Gingell, Imogen
ba7b8113-3833-40d8-a879-aab3f987455d
Trávníček, Pavel M.
4aa55b9c-8f97-47c7-9361-e7843f404651

Burgess, David, Hellinger, Petr, Gingell, Imogen and Trávníček, Pavel M. (2016) Microstructure in two-and three-dimensional hybrid simulations of perpendicular collisionless shocks. Journal of Plasma Physics, 82 (4), 1-23, [905820401]. (doi:10.1017/S0022377816000660).

Record type: Article

Abstract

Supercritical collisionless perpendicular shocks have an average macrostructure determined primarily by the dynamics of ions specularly reflected at the magnetic ramp. Within the overall macrostructure, instabilities, both linear and nonlinear, generate fluctuations and microstructure. To identify the sources of such microstructure, high-resolution two-and three-dimensional simulations have been carried out using the hybrid method, wherein the ions are treated as particles and the electron response is modelled as a massless fluid. We confirm the results of earlier two-dimensional (2-D) simulations showing both field-parallel aligned propagating fluctuations and fluctuations carried by the reflected-gyrating ions. In addition, it is shown that, for 2-D simulations of the shock coplanarity plane, the presence of short-wavelength fluctuations in all magnetic components is associated with the ion Weibel instability driven at the upstream edge of the foot by the reflected-gyrating ions. In 3-D simulations we show for the first time that the dominant microstructure is due to a coupling between field-parallel propagating fluctuations in the ramp and the motion of the reflected ions. This results in a pattern of fluctuations counter-propagating across the surface of the shock at an angle inclined to the magnetic field direction, due to a combination of field-parallel motion at the Alfvén speed of the ramp and motion in the sense of gyration of the reflected ions.

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Microstructure in two- and three-dimensional hybrid simulations of perpendicular collisionless shocks - Accepted Manuscript
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Accepted/In Press date: 30 June 2016
e-pub ahead of print date: 13 July 2016
Published date: 1 August 2016

Identifiers

Local EPrints ID: 438713
URI: http://eprints.soton.ac.uk/id/eprint/438713
ISSN: 0022-3778
PURE UUID: bdb7d2d2-6d75-4eac-9525-e93bc0358316

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Date deposited: 23 Mar 2020 17:30
Last modified: 10 Dec 2020 17:31

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Contributors

Author: David Burgess
Author: Petr Hellinger
Author: Imogen Gingell
Author: Pavel M. Trávníček

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