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| Titel |
Simultaneous imaging of aurora on small scale in OI (777.4 nm) and N21P to estimate energy and flux of precipitation |
| VerfasserIn |
B. S. Lanchester, M. Ashrafi, N. Ivchenko |
| 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 ; 27, no. 7 ; Nr. 27, no. 7 (2009-07-22), S.2881-2891 |
| Datensatznummer |
250016597
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| Publikation (Nr.) |
 copernicus.org/angeo-27-2881-2009.pdf |
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| Zusammenfassung |
| Simultaneous images of the aurora in three emissions, N21P
(673.0 nm), OII (732.0 nm) and OI (777.4 nm), have been analysed;
the ratio of atomic oxygen to molecular nitrogen has been used to
provide estimates of the changes in energy and flux of
precipitation within scale sizes of 100 m, and with temporal
resolution of 32 frames per second. The choice of filters for the
imagers is discussed, with particular emphasis on the choice of
the atomic oxygen line at 777.4 nm as one of the three emissions
measured. The optical measurements have been combined with radar
measurements and compared with the results of an auroral model,
hence showing that the ratio of emission rates OI/N2 can be
used to estimate the energy within the smallest auroral
structures. In the event chosen, measurements were made from
mainland Norway, near Troms\o, (69.6 N, 19.2 E). The peak energies
of precipitation were between 1–15 keV. In a narrow curling arc,
it was found that the arc filaments resulted from energies in
excess of 10 keV and fluxes of approximately 7 mW/m2.
These filaments of the order of 100 m in width were
embedded in a region of lower energies (about 5–10 keV) and fluxes of about
3 mW/m2. The modelling results show that the method
promises to be most powerful for detecting low energy
precipitation, more prevalent at the higher latitudes of Svalbard
where the multispectral imager, known as ASK, is now installed. |
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