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Latitudinal motions of the aurora during substormsSequences of auroral images obtained with Dynamics Explorer 1 are used to investigate latitudinal motions of the aurora in substorms. Average speeds of poleward motion are about 230 m/s near local midnight for two isolated, small substorms and about 1000 m/s during an intensification within a previously active auroral oval. The speed of poleward expansion measured at about 6-min temporal resolution can differ greatly from the average speed because of the episodic development of substorms. Recovery of the high-latitude boundary of the aurora to presubstorm latitudes is first observed in the postmidnight sector. In the premidnight sector the discrete aurora can become stationary for a period of time or even continue further poleward before a retreat to lower latitudes begins. During the recovery phase, a prominent decrease in luminosities is first observed at intermediate latitudes within the auroral distribution. This region is bounded at higher latitudes by the discrete aurora and at lower latitudes by bright diffuse aurora. Given that magnetic field lines threading these auroral distributions map to the plasma sheet boundary layer and to the central plasma sheet, respectively, magnetic field lines at the intermediate auroral latitudes then map to the plasma sheet at distances of more than about 22 earth radii.
Document ID
19870053920
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Craven, J. D.
(Iowa Univ. Iowa City, IA, United States)
Frank, L. A.
(Iowa, University Iowa City, United States)
Date Acquired
August 13, 2013
Publication Date
May 1, 1987
Publication Information
Publication: Journal of Geophysical Research
Volume: 92
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
AD-A182420
Accession Number
87A41194
Funding Number(s)
CONTRACT_GRANT: NGL-16-001-002
CONTRACT_GRANT: N00014-85-K-0404
CONTRACT_GRANT: NAG5-483
Distribution Limits
Public
Copyright
Other

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