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| Titel |
A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
| VerfasserIn |
S. E. Milan, Mark Lester, J. Moen |
| 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 ; 15, no. 11 ; Nr. 15, no. 11, S.1388-1398 |
| Datensatznummer |
250013002
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| Publikation (Nr.) |
 copernicus.org/angeo-15-1388-1997.pdf |
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| Zusammenfassung |
| A poleward-progressing 630 nm optical feature
is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT) by
a meridian-scanning photometer (MSP) located at Ny Ålesund, Svalbard.
Simultaneous coherent HF radar measurements indicate a region of poleward-expanding
backscatter with rapid sunward plasma flow velocity along the MSP meridian.
Spatial maps of the backscatter indicate a stationary backscatter feature
aligned obliquely with respect to the MSP meridian, which produces an impression
of poleward-expansion as the MSP progresses to later MLT. Two interpretations of
the observations are possible, depending on whether the arc system is considered
to move (time-dependent) or to be stationary in time and apparent motion is
produced as the MSP meridian rotates underneath it (time-independent). The first
interpretation is as a poleward motion of an east-west aligned auroral arc. In
this case the appearance of the region of backscatter is not associated with the
optical feature, though the velocities within it are enhanced when the two are
co-located. The second interpretation is as a polar arc or theta aurora, common
features of the polar cap under the prevailing IMF northwards conditions. In
this case the backscatter appears as an approximately 150 km wide region
adjacent to the optical arc. In both interpretations the luminosity of the
optical feature appears related to the magnitude of the plasma flow velocity.
The optical features presented here do not generate appreciable HF coherent
backscatter, and are only identifiable in the backscatter data as a modification
of the flow by the arc electrodynamics. |
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