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Ann. Geophys., 26, 689-698, 2008
www.ann-geophys.net/26/689/2008/
© European Geosciences Union 2008
The structure of field line resonances in a dipole magnetosphere with moving plasma
D. A. Kozlov and A. S. Leonovich
Institute of Solar-Terrestrial Physics (ISTP), Russian Academy of Sciences, Siberian Branch, Irkutsk, Russia
Abstract. A theoretical model of field line resonance in the magnetosphere with a dipole
magnetic field and moving plasma was constructed. Motion of medium was simulated by
its azimuthal rotation. Analytical and numerical solutions were found for MHD
equations describing the structure of field line resonances. It was shown that a
monochromatic, fast magnetosonic wave can excite several harmonics of standing
Alfvén waves on different resonant surfaces at once. The resonant surface density
is maximum in the transition layer at the magnetopause. The resonant oscillation
amplitude profile becomes asymmetric in our model in regions with a maximum gradient
of the background plasma velocity (plasmapause and magnetopause), in contrast to
models with immobile plasma. In the same regions, the phase of resonant oscillations
varies non-monotonically across the resonant surface which may serve as a detector
of such regions in geomagnetic pulsation observations.
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