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Ann. Geophys., 23, 523-533, 2005
www.ann-geophys.net/23/523/2005/
© European Geosciences Union 2005
Relation between the ring current and the tail current during magnetic storms
V. V. Kalegaev1, N. Y. Ganushkina2, T. I. Pulkkinen2, M. V. Kubyshkina3, H. J. Singer4, and C. T. Russell5
1Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow 119992, Russia
2Geophysical Research, Finnish Meteorological Institute, POBox 503, Helsinki, FIN-00101, Finland
3Institute of Physics, University of St-Petersburg, St-Petersburg, 198904, Russia
4H. J. Singer, NOAA Space Environment Center, Boulder, CO 80305–3328, USA
5Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095–1567, USA
Abstract. We study the dynamics of the magnetospheric large-scale current
systems during storms by using three different magnetospheric
magnetic field models: the paraboloid, event-oriented, and
Tsyganenko T01 models. We have modelled two storm events, one
moderate storm on 25-26 June 1998, when Dst reached -120nT
and one intense storm on 21-23 October 1999, when Dst dropped
to -250nT. We compare the observed magnetic field from GOES 8,
GOES 9, and GOES 10, Polar and Geotail satellites with the
magnetic field given by the three models to estimate their
reliability. All models demonstrated quite good agreement with
observations. Since it is difficult to measure exactly the
relative contributions from different current systems to the
Dst index, we compute the contributions from ring, tail
and magnetopause currents given by the three magnetic field
models. We discuss the dependence of the obtained contributions
to the Dst index in relation to the methods used in
constructing the models. All models show a significant tail
current contribution to the Dst index, comparable to the ring
current contribution during moderate storms. The ring current
becomes the major Dst source during intense storms.
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