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| Titel |
Energy and flux variations across thin auroral arcs |
| VerfasserIn |
H. Dahlgren, B. Gustavsson, B. S. Lanchester, N. Ivchenko, U. Brandstrom, D. K. Whiter, T. Sergienko, I. Sandahl, G. Marklund |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 10 ; Nr. 29, no. 10 (2011-10-04), S.1699-1712 |
| Datensatznummer |
250017099
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| Publikation (Nr.) |
 copernicus.org/angeo-29-1699-2011.pdf |
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| Zusammenfassung |
| Two discrete auroral arc filaments, with widths of less than 1 km, have been
analysed using multi-station, multi-monochromatic optical observations from
small and medium field-of-view imagers and the EISCAT radar. The energy and
flux of the precipitating electrons, volume emission rates and local electric
fields in the ionosphere have been determined at high temporal (up to 30 Hz)
and spatial (down to tens of metres) resolution. A new time-dependent
inversion model is used to derive energy spectra from EISCAT electron density
profiles. The energy and flux are also derived independently from optical
emissions combined with ion-chemistry modelling, and a good agreement is
found. A robust method to obtain detailed 2-D maps of the average energy and
number flux of small scale aurora is presented. The arcs are stretched in the
north-south direction, and the lowest energies are found on the western,
leading edges of the arcs. The large ionospheric electric fields (250 mV m−1)
found from tristatic radar measurements are evidence of strong currents
associated with the region close to the optical arcs. The different data sets
indicate that the arcs appear on the boundaries between regions with
different average energy of diffuse precipitation, caused by pitch-angle
scattering. The two thin arcs on these boundaries are found to be related to
an increase in number flux (and thus increased energy flux) without an
increase in energy. |
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