Intensification and fading of auroral arcs in the dusk-midnight sector of the polar cap

Journal Article · Wed May 01 04:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA00256· OSTI ID:5190033

Wu, Q; Rosenberg, T J ^[1]; Berkey, F T ^[2]; Eather, R H ^[3]

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1. Univ. of Maryland, College Park (USA)
2. Utah State Univ., Logan (USA)
3. Boston College, Chestnut Hill, MA (USA)

Observations of the aurora from South Pole station (magnetic latitude = {minus}74.2{degree}) have been used to study the intensification and fading of polar arcs observed near the dusk meridian. Most of the cases examined have the following features in common: (1) a preexisting auroral form intensifies for about 10 min; (2) this activation is followed by a pronounced decrease of luminosity; (3) the auroral fade terminates after 30-60 min with the onset of intense aurora which sweeps rapidly overhead. The availability of all-sky camera, auroral electrojet (AE) index and interplanetary magnetic field (IMF) data for some of the cases enables the following additional characterizations of these events. The preexisting form is a Sun- or oval-aligned arc (or part of a multiple arc system) which disappears following the activation; equatorward drift of the arc (or system) accompanies the luminosity change. There is some evidence to suggest that the arc is poleward of the auroral oval. The brief intensification and/or the onset of fading occurs during the growth phase or near the start of the expansive phase of a substorm; termination of the fade is near the maximum in AE and is probably indicative of the beginning of the recovery phase of the substorm. For all three cases for which IMF data were available the onset of fading occurred 20-30 min after B{sub z} turned southward. Sun-aligned arcs are a common feature of the polar cap during northward B{sub z} but disappear during the increasingly disturbed conditions that accompany southward B{sub z}. The present results suggest that brief intensifications of southern hemisphere polar cap arcs near dusk may be linked in part to the sunward orientation of the IMF which favors enhanced electron fluxes in the southern lobe of the magnetotail.

• OSTI ID: 5190033
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A5; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
CHARGED-PARTICLE PRECIPITATION
CURRENTS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
EARTH PLANET
ELECTRIC CURRENTS
ELECTROJETS
ELECTRON PRECIPITATION
EXPANSION
INTERPLANETARY MAGNETIC FIELDS
LUMINOSITY
MAGNETIC BAYS
MAGNETIC FIELDS
MAGNETOTAIL
MORPHOLOGY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLANETS
POLAR-CAP AURORAE
SOUTHERN HEMISPHERE
VARIATIONS