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Cyclic behavior at quasi‐parallel collisionless shocks
Author(s) -
Burgess D.
Publication year - 1989
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl016i005p00345
Subject(s) - thermalisation , mach number , shock (circulatory) , physics , mechanics , ion , magnetic field , atomic physics , quantum mechanics , medicine
Large scale one‐dimensional hybrid simulations with resistive electrons have been carried out of a quasi‐parallel ( θ Bn = 30°) high Mach number collisionless shock. The shock initially appears stable, but then exhibits cyclic behavior. For the magnetic field the cycle consists of a period when the transition from upstream to downstream is steep and well defined, followed by a period when the shock transition is extended and perturbed. This cyclic shock solution results from upstream perturbations, caused by backstreaming gyrating ions, convecting into the shock. The cyclic re‐formation of a sharp shock transition can allow ions, at one time upstream because of reflection or leakage, to contribute to the shock thermalization. The simulations are simplistic in a number of ways for the quasi‐parallel shock, but their results suggest a model which may explain qualitatively several features of observations.