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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 1
Ann. Geophys., 15, 17–23, 1997
https://doi.org/10.1007/s00585-997-0017-2
© European Geosciences Union 1997
Ann. Geophys., 15, 17–23, 1997
https://doi.org/10.1007/s00585-997-0017-2
© European Geosciences Union 1997

  31 Jan 1997

31 Jan 1997

Some evidence of ground power enhancements at frequencies of global magnetospheric modes at low latitude

P. Francia and U. Villante P. Francia and U. Villante
  • Dipartimento di Fisica, Universita' dell'Aquila, I-L'Aquila, Italy

Abstract. A statistical analysis of the power spectra of the geomagnetic field components H and D for periods ranging between 3 min and 1 h was conducted at a low-latitude observatory (L'Aquila, L=1.6) at the minimum and maximum of the solar cycle. For both components, during daytime intervals, we found evidence of power enhancements at frequencies predicted for global modes of the Earth\'s magnetosphere and occasionally observed at auroral latitudes in the F-region drift velocities (approximately at 1.3, 1.9, 2.6, and 3.4 mHz). Nighttime observations reveal a relative low frequency H enhancement associated with the bay occurrence together with a peak in the H/D power ratio which sharply emerges at 1.2 mHz in the premidnight sector. The strong similarity between solar minimum and maximum suggests that these modes can be considered permanent magnetospheric features. A separate analysis on a two-month interval shows that the observed spectral characteristics are amplified by conditions of high-velocity solar wind.

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