Nonlinear resonance theory of Pc 3 magnetic pulsation
Compressional Pc 3 magnetic pulsations with large wave numbers normal to the static magnetic field in the magnetosphere and the beating type Pc 3 pulsations on the ground are hardly interpreted with respect to the linear resonance theory based on the idea of a resonance coupling between a monochromatic surface wave at the magnetopause and a shear Alfven wave at a local field line in the inner magnetosphere. A parametric excitation of an Alfven wave (k/sup A/, ..omega../sub A/) by a magnetosonic pump wave (k/sup tsf/s/sub 1/, ..omega../sub 1f/s), which propagates obliquely to the static magnetic field, has been analyzed. The resonance conditions are chosen such that k/sup tsf/s/sub 1/ = k/sup tsf/s/sub 2/+k/sup A/ and ..omega../sub 1f/s-..omega../sub A/ = deltaapprox...omega../sub 2f/s. For both standing and propagating pumps the growth rates of the excited HM waves depend not only on the pump power but also on ..beta... It is found that large growth rates of parametric excitation of Alfven waves by the fast magnetosonic pump waves arise if theta/sub 1f/ = angle(k/sup tsf//sub 1/, B/sub 0/) approx.70/sup 0/--80/sup 0/ and the regions of parametric excitation are localized at the resonance point in the magnetosphere where ..beta..approx.m/sub e//m/sub i/. It is concluded that parametric excitation of Pc 3 range HM waves is a more attractive theory of the beating type geomagnetic pulsations than the linear resonance theory.
- Research Organization:
- Onagawa Magnetic Observatory and Geophysical Institute, Tohoku University, Sendai 980, Japan
- OSTI ID:
- 7062966
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 87:A7
- Country of Publication:
- United States
- Language:
- English
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