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Ann. Geophys., 23, 2621-2634, 2005
www.ann-geophys.net/23/2621/2005/
© European Geosciences Union 2005
Unusual strong quasi-monochromatic ground Pc5 geomagnetic pulsations in the recovery phase of November 2003 superstorm
N. G. Kleimenova1, O. V. Kozyreva1, J. Manninen2, and A. Ranta2
1Institute of the Physics of the Earth RAS, B. Gruzinskaya 10, Moscow, 123995, Russia
2Sodankylä Geophysical Observatory, Tähteläntie 62, FIN-99600 Sodankylä, Finland
Abstract. Unusually large-amplitude morning Pc5 magnetic pulsations during the
recovery phase of the huge magnetic storm in November 2003 have been studied
by using ground-based multi-point observations. Two main spectral Pc5
enhancements were observed: at f≈2 mHz, which featured slowly
increasing frequency with decreasing latitude, and at f≈3 mHz, which
was latitude independent. The Pc5 pulsations were observed at wide range of
latitudes (more than 10°) with the same very strong amplitude (up to
500nT) and with the same polarization. Only the 3-mHz peak was clearly seen in
the spectra of pulsating auroral radio absorption, as observed by the Finnish
riometer chain. Short and localized bursts of PiB (f~50–100 mHz)
magnetic pulsations and simultaneous short bursts of energetic electron
precipitation were observed in the morning sector, as well. The beginning of
the large-amplitude morning Pc5 activity occurred simultaneously with a
substorm onset in the evening and midnight sectors. However, the spectra of
pulsations in the morning and evening sectors were different. They were
compared with spectra of IMF and solar wind parameters, measured by ACE
spacecraft. The similarity between the spectra of morning Pc5 and IMF By was
found, but the spectra of evening Pi3 pulsations were similar to the spectra
of solar wind density variations. The Pc5 and PiB pulsations, as well as
bursts of the auroral radio absorption, suddenly disappeared, when the solar
wind density abruptly dropped. We suppose that the ~2-mHz Pc5
geomagnetic pulsations could be attributed to field line resonance (FLR),
however, the 3-mHz oscillations were apparently non-resonance origin.
Keywords. Magnetospheric physics (MHD waves and instabilities;
Solar wind-magnetosphere interaction; Storms
and substorms)
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