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| Titel |
Statistical study of inverted-V structures in FAST data |
| VerfasserIn |
N. Partamies, E. Donovan, D. Knudsen |
| 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 ; 26, no. 6 ; Nr. 26, no. 6 (2008-06-11), S.1439-1449 |
| Datensatznummer |
250016116
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| Publikation (Nr.) |
 copernicus.org/angeo-26-1439-2008.pdf |
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| Zusammenfassung |
Since the 1970s the inverted-V structures have been observed in the
satellite-borne particle data. These Λ-shaped enhancements of
the differential energy flux on the high energy channels on the top of low
number flux on the lower energies are traces of auroral
particle acceleration by U-shaped potential drops along the field
lines within the auroral zones. In this study, we show the results of
a statistical study of inverted-V events in five years (1997–2001) of
the Fast Auroral SnapshoT (FAST) electron spectrograms. We
found 588 well-defined events in total, but the statistical results are also shown for a
subset of 97 very best events.
The statistical analysis shows that the inverted-V's mainly occur
within the auroral oval latitudes (65°–75°
invariant latitude), in the pre-midnight sector (21–23 magnetic local
time) and during the Northern Hemisphere winter months (November to February). The typical
maximum energies of the inverted-V's are 2–4 keV, when a threshold
value of 0.3 keV is used as a selection criterion. This corresponds to
an acceleration potential drop of a few kV. The typical peak energy tends
to increase towards the magnetic midnight. Most of the inverted-V events occur
during magnetically quiet or moderate activity, Kp 1–4. The usual
width of an inverted-V varies from 20 to 40 km and is comparable to the
peak value of the typical meso-scale auroral arc width of 10–20 km. Furthermore,
the polar cap potential values estimated from the SuperDARN radar data
are always at least three times larger than the inverted-V
acceleration potential drop. |
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