Computer Science
Scientific paper
Oct 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008ge%26ae..48..606v&link_type=abstract
Geomagnetism and Aeronomy, Volume 48, Issue 5, pp.606-614
Computer Science
94.20. Ac
Scientific paper
Special methods for processing TV images have been used to study the characteristics of nighttime auroras based on the observations at high-latitude observatories on Spitsbergen. Weak subvisual auroras (SVAs), originating 3°-4° north of brighter auroras in the auroral oval, have been detected in the interval 1900-0400 MLT. The average lifetime of SVAs is approximately 7 min, and the average velocity of the equatorward shift is ˜0.6 km/s. SVAs were observed during relatively quiet periods, when the IMF B z component is mainly positive. However, SVAs are not polar-cap auroras since they are oriented from east to west rather than toward the Sun. The optical observations indicate that the SVA intensity is 0.2-0.5 and 0.1-0.3 kR in the 630 and 557.7 nm emissions, respectively. The average ratio of the emission intensities ( I 5577/ I 6300) is about 0.5. According to the direct satellite observations, the SVA electron spectrum has a maximum at 0.4-1.0 keV. In this case the energy flux of precipitating electrons is approximately an order of magnitude as low as such a flux in brighter auroral arcs in the auroral oval.
Kornilov I. A.
Kornilova T. A.
Lybekk Bjørn
Sandholt Per Even
Vorobjev Vyacheslav G.
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