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Record 6 of 26131
Two Types of Transpolar Arc Development, Event Studies with Data Set of ASTRID-2, DMSP, FAST, and SuperDARN
Author and Affiliation:
Narita, Yasuhito(Technische Univ., Inst. fuer Geophysik und Meteorologie, Brunswick, Germany)
Maezawa, Kiyoshi(Institute of Space and Astronautical Science, Sagamihara, Japan)
Toshinori, Mukai(Institute of Space and Astronautical Science, Sagamihara, Japan)
Kullen, A.(Royal Inst. of Tech., Alfven Lab., Sweden)
Ivchenko, N.(Royal Inst. of Tech., Alfven Lab., Sweden)
Marklund, G.(Royal Inst. of Tech., Alfven Lab., Sweden)
Frederick, R.(Air Force Research Lab., United States)
Carlson, C. W.(California Univ., Space Science Lab., Berkeley, CA United States)
Spann, J. F.(NASA Marshall Space Flight Center, Huntsville, AL United States)
Parks, G. K.(Washington Univ., Dept. of Geophysics, United States) Show more authors
Abstract: Aurorae which appear in the polar cap are called transpolar arcs, polar cap arcs, sun-aligned arcs, or occasionally Theta-aurora because of its spatial distribution resembling Greek character 'Theta.' Morphology, IMF (Interplanetary Magnetic Field) relationship, and ionospheric convection patterns were studied in quest of mechanisms of transpolar arcs. Four events were analyzed: 1999/Jan/22/19:00 - 23/01:30 (1 event: a) 1999/Jan/24/06:00 - 10:00 (1 event: b) 1999/Feb/1 1/20:00 - 12/02:00 (2 events: c, d), with data set of ExB drift velocity data obtained by electric field measurements of ASTRID-2 and FAST, DMSP ion driftmeter data, and line-of-sight velocity data of SuperDARN. POLAR-UVI image data were used for spatial and temporal variations of transpolar arcs and ACE data set were used for investigation of IMF relationship. IMF-Bz was strongly positive (Bz from +8nT to +20 nT) during periods of all four transpolar arcs. In events (a),(b),(c), transpolar arcs appeared immediately after the direction of IMF turned northward, though IMF was fluctuating in event (b). A sudden increase of IMF-By, from +3nT to +18nT, was observed in event (d). Two different types of transpolar arc development were observed in POLAR-UVI: one which begins as a split from dawn or dusk sector of auroral oval and shifts poleward in event (a),(c),(d), and another which is initially a patch of auroral oval disturbed by substorm but develops as a transpolar arc, forming a growing finger-like shape from midnight sector (event b). Sunward flow, associated with positive IMF-Bz, were observed within newly-created polar caps in event (a),(c),(d). Not clear ionospheric convection pattern was seen across the polar cap arc in event (b) die to limitation of data set. In event (c), O+ with energy more than 1 keV were observed by FAST within a transpolar arc, suggesting that their origin be from plasma sheet. Transpolar arcs are thought to be projection of plasma sheet bifurcation into lobe regime. There can be several ways of development of transpolar arcs and two different patterns were observed through this work.
Publication Date: Jan 01, 2002
Document ID:
(Acquired Jun 14, 2002)
Subject Category: GEOPHYSICS
Document Type: Preprint
Meeting Information: European Geophysical Society Conference; 22-26 Apr. 2002; Nice; France
Meeting Sponsor: European Geophysical Society; Unknown
Financial Sponsor: NASA Marshall Space Flight Center; Huntsville, AL United States
Organization Source: NASA Marshall Space Flight Center; Huntsville, AL United States
Description: 2p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
Availability Source: Other Sources
Availability Notes: Abstract Only
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