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Ann. Geophys., 24, 1455-1468, 2006
www.ann-geophys.net/24/1455/2006/
© European Geosciences Union 2006
ULF fluctuations of the geomagnetic field and ionospheric sounding measurements at low latitudes during the first CAWSES campaign
U. Villante1, M. Vellante1, P. Francia1, M. De Lauretis1, A. Meloni1, P. Palangio1, B. Zolesi1, M. Pezzopane1, M. Förster2, T. L. Zhang3, W. Magnes3, P. Nenovski4, I. Cholakov4, and V. Wesztergom5
1Consorzio Area di Ricerca in Astrogeofisica, L’Aquila, Italy
2GeoForschungsZentrum, Potsdam, Germany
3Space Research Institute, Austrian Academy of Sciences, Graz, Austria
4Geophysical Institute, Bulgarian Academy of Science, Sofia, Bulgaria
5Geodetic and Geophysical Research Institute of the Hungarian Academy of Science, Sopron, Hungary
Abstract. We present an analysis of ULF geomagnetic field
fluctuations at low latitudes during the first CAWSES campaign
(29 March-3 April 2004). During the whole campaign, mainly in the prenoon sector, a
moderate Pc3-4 pulsation activity is observed, clearly related to
interplanetary upstream waves. On 3 April, in correspondence to the Earth's
arrival of a coronal mass ejection, two SIs are observed whose waveforms are
indicative of a contribution of the high-latitude ionospheric currents to
the low-latitude ground field. During the following geomagnetic storm, low
frequency (Pc5) waves are observed at discrete frequencies. Their
correspondence with the same frequencies detected in the radial components
of the interplanetary magnetic field and solar wind speed suggests that
Alfvénic solar wind fluctuations may act as direct drivers of
magnetospheric fluctuations. A cross-phase analysis, using different pairs of
stations, is also presented for identifying field line resonant frequencies
and monitoring changes in plasmaspheric mass density. Lastly, an
analysis of ionospheric vertical soundings, measured at the Rome ionosonde
station (41.8° N, 12.5° E), and vertical TEC measurements deduced
from GPS signals within an European network shows the relation between the ULF
resonances in the inner magnetosphere and thermal plasma density variations
during geomagnetically quiet conditions, in contrast to various storm phases
at the end of the CAWSES campaign.
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