Latitudinal motions of the aurora during substorms

Journal Article · Fri May 01 00:00:00 EDT 1987 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA092iA05p04565· OSTI ID:5398739

Craven, J D; Frank, L A ^[1]

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1. Univ. of Iowa, Iowa City (United States)

Sequences 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 {approximately}230 m/s near local midnight for two isolated, small substorms and {approximately} 1,000 m/s during an intensification within a previously active auroral oval. The speed of poleward expansion measured at {approximately}6-min temporal resolution can differ greatly from the average speed because of the episodic development of substorms. This poleward motion may be influenced by the sign of the z component of the interplanetary magnetic field. Recovery of the high-latitude boundary of the aurora to presubstorm latitudes is first observed in the postmidnight 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. For these substorms the expansion and recovery phases are not separated by a {approximately}5{degree} poleward leap of the aurora. During the recovery phase a prominent decrease in luminosities is first observed at intermediate latitudes within the auroral 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 {approx gt}22 R{sub E}.

• OSTI ID: 5398739
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 92:A5; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
AURORAL OVAL
BOUNDARY LAYERS
DATA ANALYSIS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
EXPANSION
EXPLORER SATELLITES
GEOGRAPHICAL VARIATIONS
IMAGES
INTERPLANETARY MAGNETIC FIELDS
LATITUDE EFFECT
LAYERS
LUMINOSITY
MAGNETIC BAYS
MAGNETIC FIELDS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLASMA SHEET
SATELLITES
TIME DEPENDENCE
VARIATIONS