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Ann. Geophys., 21, 923-932, 2003
www.ann-geophys.net/21/923/2003/
© European Geosciences Union 2003
Low frequency geomagnetic field variations at Dome C (Antarctica)
S. Lepidi1, L. Cafarella2, P. Francia3, A. Meloni2, P. Palangio1, and J. J. Schott4
1Istituto Nazionale di Geofisica e Vulcanologia, L’Aquila, Italy
2Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy
3Dipartimento di Fisica, Università dell’Aquila, L’Aquila, Italy
4EOST, IPG, Strasbourg, France
Abstract. We conduct an analysis of
the geomagnetic field variations recorded at the new Antarctic station Dome C,
located very close to the geomagnetic pole, which has been operating for
approximately one month during the 1999–2000 campaign. We also perform a
comparison with simultaneous measurements at the Italian Antarctic station
Terra Nova Bay, in order to investigate the spatial extension of the phenomena
observed at very high latitude. Our results show that between the two stations
the daily variation is similar and the fluctuations with f ~ 1 mHz are
coherent, provided that in both cases the comparison is made between
geographically oriented components, suggesting that ionospheric currents
related to the geographic position, more than field-aligned currents, are
responsible for the lowest frequency variations; conversely, higher frequency
(Pc5) fluctuations are substantially decoupled between the two stations. We
also found that at Dome C the fluctuation power in the 0.55–6.7 mHz frequency
band is well related with the solar wind speed during the whole day and that at
Terra Nova Bay the correlation is also high, except around local geomagnetic
noon, when the station approaches the polar cusp. These results indicate that
the solar wind speed control of the geomagnetic field fluctuation power is very
strict in the polar cap and less important close to the polar cusp.
Key words. Magnetospheric physics (MHD
waves and instabilities; Polar cap phenomena; Solar wind-magnetosphere
interactions)
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