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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 2
Ann. Geophys., 20, 151-159, 2002
https://doi.org/10.5194/angeo-20-151-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 20, 151-159, 2002
https://doi.org/10.5194/angeo-20-151-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

  28 Feb 2002

28 Feb 2002

Case studies on the dynamics of Pi3 geomagnetic and riometer pulsations during auroral activations

N. G. Kleimenova1, O. V. Kozyreva1, K. Kauristie2, J. Manninen3, and A. Ranta3 N. G. Kleimenova et al.
  • 1Institute of the Earth Physics, Moscow 123995, Russia
  • 2Finnish Meteorological Institute, Geophysical Research Division, P.O. Box 503, FIN-00101 Helsinki, Finland
  • 3Oulu University, Sodankylä Geophysical Observatory, FIN-99600 Sodankylä, Finland
  • Correspondence to: N. Kleimenova
  • (kleimen@uipe-ras.scgis.ru)

Abstract. A sequence of three subsequent auroral activations (at 18:10, 19:48 and 20:00 UT) on 9 February 1997 is analysed. The brightenings of optical auroras were collocated with latitudinally localized bursts of pulsating riometer absorption and Pi3 geomagnetic pulsations. In two of the cases, the strongest westward directed electrojet currents and the footpoint of the upward directed field-aligned currents related to the auroral brightening were observed in the same region as the largest amplitude of the pulsations and their polarization changed. In the third case, field-aligned current signatures were present, but not so pronounced that their accurate location could not be defined. In all cases, the spectra of geomagnetic and absorption pulsations were similar. Based on ground-based observations alone, it is difficult to say whether the energetic particle precipitation (riometer absorption) was modulated by the geomagnetic pulsations or whether the geomagnetic pulsations were caused by varying ionospheric currents controlled by the precipitating particle intensity. However, the localized nature of both pulsations of the two different phenomena and their tight coupling with each other seem to support the latter option.

Key words. Ionosphere (Particle precipitation) – Magnetospheric physics (auroral phenomena; MHD waves and instabilities)

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