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Ann. Geophys., 22, 2345-2353, 2004
www.ann-geophys.net/22/2345/2004/
© European Geosciences Union 2004
Nonstationarity of quasi-perpendicular shocks: a comparison of full particle simulations with different ion to electron mass ratio
M. Scholer and S. Matsukiyo
Max-Planck-Institut für Extraterrestrische Physik, 85741 Garching, Germany
Abstract. We have performed 3 one-dimensional full particle electromagnetic
simulations of a quasi-perpendicular shock with the same Alfvén
Mach number MA=4.5, shock normal - magnetic field angle ΘBn=87°, and ion and electron beta (particle to magnetic field
pressure) of 0.05, but with different ion to electron mass ratios
(mi/me=80, 400, 1840). At high ion beta it has
been shown previously that the shock is steady. At low ion beta,
as in the present simulations,
the shock periodically reforms itself. However, whereas at
unrealistically low mass ratios the reformation is due to
accumulation of specularly reflected particles at the upstream
edge of the foot, at the realistic mass ratio the modified
two-stream instability between the incoming solar wind ions and
solar wind electrons leads to ion phase mixing and thermalization.
The
reformation process is thereby considerably modified.
At the lowest mass
ratio the Buneman instability between the solar wind electrons
and the reflected ions is excited,
which is stabilized at higher mass ratios.
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