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Ann. Geophys., 21, 671-679, 2003
www.ann-geophys.net/21/671/2003/
© European Geosciences Union 2003
The properties and causes of rippling in quasi-perpendicular collisionless shock fronts
R. E. Lowe and D. Burgess
Astronomy Unit, Queen Mary, University of London, UK
Abstract. The overall structure of
quasi-perpendicular, high Mach number collisionless shocks is controlled to a
large extent by ion reflection at the shock ramp. Departure from a strictly
one-dimensional structure is indicated by simulation results showing that the
surface of such shocks is rippled, with variations in the density and all field
components. We present a detailed analysis of these shock ripples, using
results from a two-dimensional hybrid (particle ions, electron fluid)
simulation. The process that generates the ripples is poorly understood,
because the large gradients at the shock ramp make it difficult to identify
instabilities. Our analysis reveals new features of the shock ripples, which
suggest the presence of a surface wave mode dominating the shock normal
magnetic field component of the ripples, as well as whistler waves excited by
reflected ions.
Key words. Space plasma physics
(numerical simulation studies; shock waves; waves and instabilities)
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