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Ann. Geophys., 21, 709-717, 2003
www.ann-geophys.net/21/709/2003/
© European Geosciences Union 2003
April 2000 geomagnetic storm: ionospheric drivers of large geomagnetically induced currents
A. Pulkkinen1, A. Thomson2, E. Clarke2, and A. McKay3
1Finnish Meteorological Institute, Geophysical Research Division, P.O. Box 503, FIN-00101, Finland
2British Geological Survey, Edinburgh, EH9 3LA, UK
3Department of Geology and Geophysics, University of Edinburgh, EH9 3JW, UK
Abstract. Geomagnetically induced
currents (GIC) flowing in technological systems on the ground are a direct
manifestation of space weather. Due to the proximity of very dynamic
ionospheric current systems, GIC are of special interest at high latitudes,
where they have been known to cause problems, for example, for normal operation
of power transmission systems and buried pipelines. The basic physics
underlying GIC, i.e. the magnetosphere – ionosphere interaction and
electromagnetic induction in the ground, is already quite well known. However,
no detailed study of the drivers of GIC has been carried out and little is
known about the relative importance of different types of ionospheric current
systems in terms of large GIC. In this study, the geomagnetic storm of 6–7
April 2000 is investigated. During this event, large GIC were measured in
technological systems, both in Finland and in Great Britain. Therefore, this
provides a basis for a detailed GIC study over a relatively large regional
scale. By using GIC data and corresponding geomagnetic data from north European
magnetometer networks, the ionospheric drivers of large GIC during the event
were identified and analysed. Although most of the peak GIC during the storm
were clearly related to substorm intensifications, there were no common
characteristics discernible in substorm behaviour that could be associated with
all the GIC peaks. For example, both very localized ionospheric currents
structures, as well as relatively large-scale propagating structures were
observed during the peaks in GIC. Only during the storm sudden commencement at
the beginning of the event were large-scale GIC evident across northern Europe
with coherent behaviour. The typical duration of peaks in GIC was also quite
short, varying between 2–15 min.
Key words. Geomagnetism and
paleo-magnetism (geomagnetic induction) – Ionosphere (ionospheric
disturbances) – Magnetospheric physics (storms and substorms)
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