JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO.
A3, 1098,
Slow drift
mirror modes in finite electron-temperature plasma: Hydrodynamic and
kinetic drift mirror instabilities
Oleg A. Pokhotelov
Institute of
Physics of the Earth, Russian Academy of
Science,
Moscow, Russia
Ingmar Sandberg
Department of
Astronomy and Space Physics, Uppsala
University,
Uppsala, Sweden
Roald Z. Sagdeev
Department of
Physics, University of Maryland,
College Park, Maryland,
USA
Rudolf A. Treumann
Centre for
Interdisciplinary Plasma Science, Max-Planck-Institute
for extraterrestrial Physics, Garching,
Germany
Oleg G. Onishchenko
Institute of
Physics of the Earth, Russian Academy of
Science,
Moscow, Russia
Michael A. Balikhin
Department of
Automatic Control and Systems Engineering, Sheffield
University,
Sheffield, UK
Vladimir P. Pavlenko
Department of
Astronomy and Space Physics, Uppsala
University,
Uppsala, Sweden
Abstract
[1] We
develop a
fully kinetic linear theory of the drift mirror (DM) instability
accounting for arbitrary particle velocity distribution functions
including nonzero electron temperature effects and plasma pressure
anisotropy. In the quasi-hydrodynamic limiting case the theory
reproduces the results obtained for the ion mirror instability.
However, for the very low frequency electron DM modes which can develop
in a nonuniform plasma of nonzero electron temperature, Te
0, such an equivalence does not exist. We refer to these modes as slow
drift mirror (SDM) modes in order to distinguish them from the
conventional ion-DM mode. Two new instabilities, one hydrodynamic and
one kinetic, that lead to the growth of SDM modes are found in the
fully kinetic regime. The first instability develops for values of the
ion anisotropy lower than required for the classical ion-DM
instability. The second instability occurs when the conditions for the
ion-DM instability are satisfied as well. The frequency of the SDM mode
is less than the frequency of the ion-DM mode, DM ~
n,
where n
is the density gradient-drift frequency of the ions. However, when the
electron temperature is of the order of the parallel ion temperature,
the SDM instability growth rate may become comparable or even higher
than that of the ion-DM instability. The free energy necessary for
these new instabilities is taken from two sources. The main source is
the energy stored in the ion pressure anisotropy. The second source is
the electron pressure gradient which builds up in a plasma of nonzero
electron temperature.
Received 17 August 2002;
revised 30 October 2002; accepted 23 December 2002; published 7
March 2003.
Keywords: drift
mirror mode, electron mirror mode, kinetic mirror mode, slow mirror
mode, magnetic turbulence.
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