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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 10
Ann. Geophys., 22, 3583-3588, 2004
https://doi.org/10.5194/angeo-22-3583-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 3583-3588, 2004
https://doi.org/10.5194/angeo-22-3583-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  03 Nov 2004

03 Nov 2004

On the semiannual and annual variations of geomagnetic activity and components

J.-L. Le Mouël1, E. Blanter2, A. Chulliat1, and M. Shnirman2 J.-L. Le Mouël et al.
  • 1Laboratoire de Géomagnétisme, Institut de Physique du Globe de Paris, 4 place Jussieu, 75252 Paris cedex 05, France
  • 2International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Warshavskoye sh. 79 kor. 2, Moscow 113556, Russia

Abstract. The semiannual and annual lines in a long series of magnetic observatories daily values, as well as in the aa-activity index series, are investigated. For both periods, amplitudes and phases of the lines corresponding to the different series present grossly common variations on decadal time scales; relative phases and amplitude ratios between the observatories change with the same time constants. The results are briefly discussed with regards to commonly received theories of the semiannual variation of magnetic activity, and some possible mechanisms for the observed geographical variability are suggested.

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