The large-scale current system during auroral substorms

We present an empirical model of the equivalent current system in the ionosphere during the peak of a classical bulge-type auroral sub storm. This model is derived from measurements made by ~110 ground magnetometer stations during 116 substorms. The data are temporally and spatially organized using...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2014-06, Vol.119 (6), p.4591-4606
Main Authors: Gjerloev, J. W., Hoffman, R. A.
Format: Article
Language:English
Subjects:
Astrophysics
Auroral oval
Auroral substorms
Auroral zones
Auroras
currents
Electrojets
Empirical models
Equatorial regions
Equivalence
Geophysics
Ground stations
Ionosphere
Magnetosphere
Magnetospheres
Polar caps
Scale (ratio)
substorm
Wedges
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Summary:We present an empirical model of the equivalent current system in the ionosphere during the peak of a classical bulge-type auroral sub storm. This model is derived from measurements made by ~110 ground magnetometer stations during 116 substorms. The data are temporally and spatially organized using global auroral images obtained by the Polar Visible Imaging System Earth Camera. The empirical equivalent current system displays three key features: a poleward shift of the westward electrojet connecting the postmidnight and premidnight components; a polar cap swirl; and significantly different magnitudes of the postmidnight and premidnight westward electrojets. This leads us to propose a two-wedge current system linking the ionosphere to the magnetosphere. The bulge current wedge is located in the premidnight region just equatorward of the open-closed field line boundary while another three-dimensional current system is located in the postmidnight region well within the auroral oval. We use Biot and Savart calculations and Tsyganenko mapping and show that this new model is a likely solution for the large-scale current system.
ISSN:2169-9380
2169-9402
2169-9402
DOI:10.1002/2013JA019176