ANGEO

Annales Geophysicae

ANGEO

Ann. Geophys.

1432-0576

Springer Verlag

Göttingen, Germany

10.1007/s00585-998-0900-5

Standing Alfvén waves with m ≫ 1 in an axisymmetric magnetosphere excited by a stochastic source

Leonovich

A. S.

¹ Mazur

V. A.

Institute of Solar-Terrestrial Physics, Russian Academy of Science, Siberian Branch, Irkutsk 33, PO Box 4026, 664033 Russia

31 08 1998

16 8 900 913

1998

This article is available from https://angeo.copernicus.org/articles/16/900/1998/angeo-16-900-1998.html

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In the framework of an axisymmetric magnetospheric model, we have constructed a theory for broad-band standing Alfvén waves with large azimuthal wave number m » 1 excited by a stochastic source. External currents in the ionosphere are taken as the oscillation source. The source with statistical properties of "white noise" is considered at length. It is shown that such a source drives oscillations which also have the "white noise" properties. The spectrum of such oscillations for each harmonic of standing Alfvén waves has two maxima: near the poloidal and toroidal eigenfrequencies of the magnetic shell of the observation. In the case of a small attenuation in the ionosphere the maximum near the toroidal frequency is dominated, and the oscillations are nearly toroidally polarized. With a large attenuation, a maximum is dominant near the poloidal frequency, and the oscillations are nearly poloidally polarized.< Key words. Ionosphere-magnetosphere interaction · Wave propagation · Magnetospheric physics · MHD waves and instabilities