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Ann. Geophys., 25, 1131-1139, 2007
www.ann-geophys.net/25/1131/2007/
© European Geosciences Union 2007
Features of stable diffuse arcs observed by means of auroral tomography
Zh. V. Dashkevich, V. E. Ivanov, and B. Z. Khudukon
Polar Geophysical Institute, 14 Fersmana St., 184209 Apatity, Russia
Abstract. In this paper we study the spatial distribution of optical volume emission
rates and peculiarities of the luminosity intensity within weak diffuse
auroral arcs recovered by means of auroral tomography. The tomographic
images are obtained from sets of scanning multi-channel photometer data
obtained in February 1999 on the Kola Peninsula in Russia at three sites of
a chain extending 226 km along the geomagnetic meridian. The 427.8- and
557.7-nm emissions of a 15-s time resolution observed within one hour during
low geomagnetic activity are analyzed. We found that the intensity profile
of an individual arc along the geomagnetic meridian has an inverted-V-shape.
The luminosity maximum altitude decrease by 4–14 km at about 140 km distance
in the south-north direction can be observed during two or more diffuse
arcs. The parameters of the precipitating electron flux are obtained from an
integral equation, which determines the best relationship between the 427.8-nm
intensity height profile and an arbitrary particle energy spectrum. A
dimensionless function of the energy dissipation is used as the core in the
integral equation. The estimated average energy of electron flux, which
generated the isolated diffuse arc, is 1–2 keV higher in the central part of
the arc in comparison to values at its borders.
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