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| Titel |
Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1 |
| VerfasserIn |
C. Xiong, H. Lühr, H. Wang, M. G. Johnsen |
| 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 ; 32, no. 6 ; Nr. 32, no. 6 (2014-06-04), S.609-622 |
| Datensatznummer |
250121067
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| Publikation (Nr.) |
 copernicus.org/angeo-32-609-2014.pdf |
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| Zusammenfassung |
| In this paper we present the first statistical study on auroral oval
boundaries derived from small- and medium-scale field-aligned currents
(FACs, < 150 km). The dynamics of both the equatorward and poleward boundaries
is deduced from 10 years of CHAMP (CHAllenging Minisatellite Payload) magnetic field data (August 2000–August 2010).
The approach for detecting the boundaries from FACs works well under
dark conditions. For a given activity level the boundaries form well-defined
ellipses around the magnetic pole. The latitudes of the equatorward and
poleward boundaries both depend, but in different ways, on magnetic activity.
With increasing magnetic activity the equatorward boundary expands
everywhere, while the poleward boundary shows on average no dependence on
activity around midnight, which seems to be stationary at a value of about
72° Mlat. Functional relations between the latitudes of the
boundaries and different magnetic activity indices have been tested. Best
results for a linear dependence are derived for both boundaries with the
dayside merging electric field. The other indices, like the auroral electrojet
(AE) and disturbance storm time (Dst) index, also provide good linear relations but with some
caveats. Toward high activity a saturation of equatorwards expansion seems to
set in. The locations of the auroral boundaries are practically independent
of the level of the solar EUV flux and show no dependence on season. |
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