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Ann. Geophys., 25, 815-822, 2007
www.ann-geophys.net/25/815/2007/
© European Geosciences Union 2007
Polarization properties of standing shear Alfvén waves in non-axisymmetric background magnetic fields
K. Kabin, R. Rankin, I. R. Mann, A. W. Degeling, and R. Marchand
Department of Physics, the University of Alberta, Edmonton, Alberta, T6G 2G7 Canada
Abstract. In this paper we present results concerning
periods and polarizations of cold plasma ultra-low frequency (ULF)
guided Alfvén waves in a non-axisymmetric geomagnetic field.
The background geomagnetic field is approximated by a compressed dipole
for which
we propose a simple description in terms of Euler potentials.
This study is motivated by the problem of outer-radiation
belt electron acceleration by ULF waves, for which the polarization
of the wave is of paramount importance. We consider an approximation
appropriate to decoupled Alfvénic waves and
find that the
polarization of the waves can change significantly with local
time. Therefore, the ULF wave's contribution to the MeV electron
energization
process can be localized in space.
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