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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
A10216,
doi:10.1029/2007JA012544,
2007
Observations of dipolarization at geosynchronous orbits and its response in the polar cap convection during extreme southward
interplanetary magnetic field conditions
P. T. Jayachandran
Physics Department, University of New Brunswick, Fredericton, New Brunswick, Canada
J. W. MacDougall
Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada
A. M. Hamza
Physics Department, University of New Brunswick, Fredericton, New Brunswick, Canada
M. G. Henderson
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
Abstract
Analysis of the polar cap convection and geosynchronous magnetic field measurements, in the context of dipolarization events,
during extreme southward interplanetary magnetic field (IMF) conditions is presented in the paper. Clear dipolarization events
at geosynchronous orbits are always followed by an increase in the polar cap convection with a time delay. The distribution
of the time delay between the onset of dipolarization at geosynchronous orbit and polar cap convection response varied between
6 and 15 min with an average of 9 min. The polar cap convection response to the dipolarization events enabled the deduction
of the dipolarization timescales at geosynchronous orbits and in the ionosphere. A comparison of these two timescales revealed
that the timescales of dipolarization events deduced from geosynchronous magnetic field measurements were always shorter (average
11 min) than the timescales deduced from the polar cap convection measurements (average 33 min).
Received 15
May
2007;
accepted 10
September
2007;
published 19
October
2007.
Keywords: polar cap convection;
dipolarization;
substorms.
Index Terms: 2776 Magnetospheric Physics: Polar cap phenomena; 2730 Magnetospheric Physics: Magnetosphere: inner; 2760 Magnetospheric Physics: Plasma convection (2463); 2790 Magnetospheric Physics: Substorms; 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions (2431).
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Citation: Jayachandran, P. T., J. W. MacDougall, A. M. Hamza, and M. G. Henderson
(2007),
Observations of dipolarization at geosynchronous orbits and its response in the polar cap convection during extreme southward
interplanetary magnetic field conditions,
J. Geophys. Res.,
112,
A10216,
doi:10.1029/2007JA012544.
Copyright 2007 by the American Geophysical Union.
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