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| Titel |
PFISR nightside observations of naturally enhanced ion acoustic lines, and their relation to boundary auroral features |
| VerfasserIn |
R. G. Michell, K. A. Lynch, C. J. Heinselman, H. C. Stenbaek-Nielsen |
| 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. 11 ; Nr. 26, no. 11 (2008-11-19), S.3623-3639 |
| Datensatznummer |
250016297
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3623-2008.pdf |
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| Zusammenfassung |
| We present results from a coordinated camera and radar study of the auroral
ionosphere conducted during March of 2006 from Poker Flat, Alaska. The
campaign was conducted to coincide with engineering tests of the first
quarter installation of the Poker Flat Incoherent Scatter Radar (PFISR). On
31 March 2006, a moderately intense auroral arc, (~10 kR at 557.7 nm),
was located in the local magnetic zenith at Poker Flat. During
this event the radar observed 7 distinct periods of abnormally large
backscattered power from the F-region. These were only observed in the
field-aligned radar beam, and radar spectra from these seven times show
naturally enhanced ion-acoustic lines (NEIALs), the first observed with
PFISR. These times corresponded to (a) when the polar cap boundary of the
auroral oval passed through the magnetic zenith, and (b) when small-scale
filamentary dark structures were visible in the magnetic zenith. The presence
of both (a) and (b) was necessary for their occurrence. Soft electron
precipitation occurs near the magnetic zenith during these same times. The
electron density in the vicinity where NEIALs have been observed by previous
studies is roughly between 5 and 30×1010 m−3. Broad-band
extremely low frequency (BBELF) wave activity is observed in situ by
satellites and sounding rockets to occur with similar morphology, during
active auroral conditions, associated with the poleward edge of the aurora
and soft electron precipitation. The observations presented here suggest
further investigation of the idea that NEIALs and BBELF wave activity are
differently-observed aspects of the same wave phenomenon. If a connection
between NEIALs and BBELF can be established with more data, this could
provide a link between in situ measurements of downward current regions
(DCRs) and dynamic aurora, and ground-based observations of dark auroral
structures and NEIALs. Identification of in situ processes, namely wave
activity, in ground-based signatures could have many implications. One
specific example of interest is identifying and following the temporal and
spatial evolution of regions of potential ion outflow over large spatial and
temporal scales using ground-based optical observations. |
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