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Ann. Geophys., 24, 2277-2289, 2006
www.ann-geophys.net/24/2277/2006/
© European Geosciences Union 2006
Magnetosonic resonance in a dipole-like magnetosphere
A. S. Leonovich1, D. A. Kozlov1, and V. A. Pilipenko2
1Institute of Solar-Terrestrial Physics (ISTP), Russian Academy of Sciences, Siberian Branch, Irkutsk, Russia
2Institute of the Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
Abstract. A theory of resonant conversion of fast magnetosonic (FMS) waves
into slow magnetosonic (SMS) oscillations in a magnetosphere with
dipole-like magnetic field has been constructed. Monochromatic
FMS waves are shown to drive standing (along magnetic field
lines) SMS oscillations, narrowly localized across magnetic shells.
The longitudinal and transverse structures, as well as spectrum of
resonant SMS waves are determined. Frequencies of fundamental
harmonics of standing SMS waves lie in the range of 0.1–1 mHz,
and are about two orders of magnitude lower than frequencies of
similar Alfvén field line resonance harmonics. This difference
makes an effective interaction between these MHD modes
impossible. The amplitude of SMS oscillations rapidly decreases
along the field lines from the magnetospheric equator towards the
ionosphere. In this context, magnetospheric SMS oscillations
cannot be observed on the ground, and the ionosphere does not
play any role either in their generation or dissipation. The
theory developed can be used to interpret the occurrence of compressional
Pc5 waves in a quiet magnetosphere with a weak ring current.
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