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Filamentary current structures in the postnoon sector: Observations from UARSDuring an intense geomagentic storm (Kp 7+) that began at approximately 1830 UT on October 1, 1991, the Upper Atmosphere Research Satellite (UARS) satellite encountered the dayside postnoon auroral oval. On two consecutive crossings of the northern hemisphere between 2040 and 2240 UT, the vector magnetometer detected region 1 and 2 Birkeland and ionospheric currents in the postnoon sector. Low-energy electron events were observed near 1400 MLT within a narrow portion of the region 1 current system. Simultaneous magnetic field measurements revealed the presence of intense (approximately 20 microA/sq m) bipolar filament current structures embedded in the auroral oval. The upward-directed currents were associated with the more concentrated region of precipitating electrons. Ions associated with the more intense flux of low-energy electrons exhibited a dispersion signature typical of an ion velocity filter. The dispersion, aligned along the orbit, exhibited higher-energy ions at lower latitudes and earlier local times. The colocation of filament currents and ion dispersion signatures at such late postnoon local times is not consistent with typical E x B 'cusp' dispersions. These features more likely result from dayside boundary wave phenomena.
Document ID
19950053334
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Bythrow, P. F.
(Johns Hopkins University Laurel, MD, United States)
Anderson, B. J.
(Johns Hopkins University Laurel, MD, United States)
Potemra, T. A.
(Johns Hopkins University Laurel, MD, United States)
Zanetti, L. J.
(Johns Hopkins University Laurel, MD, United States)
Winningham, J. D.
(Southwest Research Institute, San Antonio, TX United States)
Chenette, D. L.
(Lockheed Palo Alto Research Laboratory, Palo Alto, CA United States)
Date Acquired
August 16, 2013
Publication Date
August 1, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: A8
ISSN: 0148-0227
Subject Category
Geosciences (General)
Accession Number
95A84933
Funding Number(s)
CONTRACT_GRANT: NAS5-27753
Distribution Limits
Public
Copyright
Other

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