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Title: Shock front instability associated with reflected ions at the perpendicular shock

Abstract

Two-dimensional hybrid simulations of perpendicular, supercritical collisionless shocks are carried out in a geometry with the magnetic field perpendicular to the simulation plane so that parallel propagating fluctuations, such as Alfven ion cyclotron waves, are suppressed. In terms of average profile and large downstream ion temperature anisotropy, the results resemble those from earlier one-dimensional hybrid simulations, and differ markedly from the results of two-dimensional simulations in which field-parallel propagating fluctuations are included. In addition, we find an instability at the shock front, in which a pattern of magnetic field and density enhancements propagates along the shock surface in the direction of gyration and at the average speed of the ions reflected at the shock. The instability mechanism depends on a spatio-temporal modulation of the fraction of reflected ions over the shock surface. The instability has a threshold that depends on the Mach number and the upstream ion plasma beta, being stabilized by an increased beta and decreased Mach number. In a realistic three-dimensional planar shock, this instability will be only one of several mechanisms contributing to shock front nonstationarity. However, at a three-dimensional curved shock, there is a region where the instability mechanism described may dominate.

Authors:
;  [1]
  1. Astronomy Unit, Queen Mary, University of London, London E1 4NS (United Kingdom)
Publication Date:
OSTI Identifier:
20960086
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2435317; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALFVEN WAVES; DENSITY; ELECTRON TEMPERATURE; FLUCTUATIONS; GEOMETRY; ION PLASMA WAVES; ION TEMPERATURE; IONS; MACH NUMBER; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; ONE-DIMENSIONAL CALCULATIONS; PLASMA; PLASMA DENSITY; PLASMA INSTABILITY; PLASMA SIMULATION; SHOCK WAVES; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Burgess, D., and Scholer, M. Shock front instability associated with reflected ions at the perpendicular shock. United States: N. p., 2007. Web. doi:10.1063/1.2435317.
Burgess, D., & Scholer, M. Shock front instability associated with reflected ions at the perpendicular shock. United States. doi:10.1063/1.2435317.
Burgess, D., and Scholer, M. Mon . "Shock front instability associated with reflected ions at the perpendicular shock". United States. doi:10.1063/1.2435317.
@article{osti_20960086,
title = {Shock front instability associated with reflected ions at the perpendicular shock},
author = {Burgess, D. and Scholer, M.},
abstractNote = {Two-dimensional hybrid simulations of perpendicular, supercritical collisionless shocks are carried out in a geometry with the magnetic field perpendicular to the simulation plane so that parallel propagating fluctuations, such as Alfven ion cyclotron waves, are suppressed. In terms of average profile and large downstream ion temperature anisotropy, the results resemble those from earlier one-dimensional hybrid simulations, and differ markedly from the results of two-dimensional simulations in which field-parallel propagating fluctuations are included. In addition, we find an instability at the shock front, in which a pattern of magnetic field and density enhancements propagates along the shock surface in the direction of gyration and at the average speed of the ions reflected at the shock. The instability mechanism depends on a spatio-temporal modulation of the fraction of reflected ions over the shock surface. The instability has a threshold that depends on the Mach number and the upstream ion plasma beta, being stabilized by an increased beta and decreased Mach number. In a realistic three-dimensional planar shock, this instability will be only one of several mechanisms contributing to shock front nonstationarity. However, at a three-dimensional curved shock, there is a region where the instability mechanism described may dominate.},
doi = {10.1063/1.2435317},
journal = {Physics of Plasmas},
number = 1,
volume = 14,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}