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Ann. Geophys., 26, 1653-1663, 2008
www.ann-geophys.net/26/1653/2008/
© European Geosciences Union 2008
Alfvén ship waves: high-m ULF pulsations in the magnetosphere generated by a moving plasma inhomogeneity
P. N. Mager and D. Yu. Klimushkin
Institute of Solar-Terrestrial Physics (ISTP), Russian Academy of Science, Siberian Branch, Irkutsk, P.O. Box 291, 664033, Russia
Abstract. The generation of a high-m Alfvén wave by substorm injected energetic
particles in the magnetosphere is studied. The wave is supposed to be emitted
by an alternating current created by the drifting particle cloud or ring
current inhomogeneity. It is shown that the wave appears in some azimuthal
location simultaneously with the particle cloud arrival at the same spot. The
value of the azimuthal wave number is determined as m~ω/ωd,
where ω is the eigenfrequency of the standing Alfvén wave and ωd
is the particle drift frequency. The wave propagates westward, in the
direction of the proton drift. Under the reasonable assumption about the density
of the energetic particles, the amplitude of the generated wave is close to
the observed amplitudes of poloidal ULF pulsations.
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