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

A. S. Leonovich (1) , V. A. Mazur (1)

1 ISTP - Institute of Solar-Terrestrial Physics [Irkutsk]

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.

Domaines: Océan, Atmosphère; Sciences de la Terre

A. S. Leonovich, V. A. Mazur. Standing Alfvén waves with m ? 1 in an axisymmetric magnetosphere excited by a stochastic source. Annales Geophysicae, 1998, 16 (8), pp.900-913. ⟨hal-00316422⟩