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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 24, issue 10
Ann. Geophys., 24, 2429–2433, 2006
https://doi.org/10.5194/angeo-24-2429-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 2429–2433, 2006
https://doi.org/10.5194/angeo-24-2429-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  20 Oct 2006

20 Oct 2006

On impulse excitation of the global poloidal modes in the magnetosphere

P. N. Mager and D. Yu. Klimushkin P. N. Mager and D. Yu. Klimushkin
  • Institute of Solar-Terrestrial Physics (ISTP), Russian Academy of Science, Siberian Branch, Irkutsk, 664033, Russia

Abstract. Through the combined action of the field line curvature and finite plasma pressure in some regions of the magnetosphere (plasmapause, ring current) there can exist global poloidal Alfvén modes standing both along field lines and across magnetic shells and propagating along azimuth. In this paper we investigate the spatio-temporal structure of such waves generated by an impulsive source. In general, the mode is the sum of radial harmonics whose structure is described by Hermitian polynomials. For the usually observed second harmonic structure along the background field, frequencies of these radial harmonics are very close to each other; therefore, the generated wave is almost a monochromatic oscillation. But mixing of the harmonics with different radial structure causes the evolution of the initially poloidal wave into the toroidal one. This casts some doubts upon the interpretation of observed high-m poloidal waves as global poloidal modes.

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