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| Titel |
On the collocation between dayside auroral activity and coherent HF radar backscatter |
| VerfasserIn |
J. Moen, H. C. Carlson, S. E. Milan, N. Shumilov, B. Lybekk, P. E. Sandholt, Mark Lester |
| 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 ; 18, no. 12 ; Nr. 18, no. 12, S.1531-1549 |
| Datensatznummer |
250014099
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| Publikation (Nr.) |
 copernicus.org/angeo-18-1531-2000.pdf |
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| Zusammenfassung |
The 2D morphology of coherent HF radar and
optical cusp aurora has been studied for conditions of predominantly southward
IMF conditions, which favours low-latitude boundary layer reconnection. Despite
the variability in shape of radar cusp Doppler spectra, the spectral width
criterion of > 220 m s–1 proves to be a robust cusp
discriminator. For extended periods of well-developed radar backscatter echoes,
the equatorward boundary of the > 220 m s–1 spectral width
enhancement lines up remarkably well with the equatorward boundary of the
optical cusp aurora. The spectral width boundary is however poorly determined
during development and fading of radar cusp backscatter. Closer inspection of
radar Doppler profile characteristics suggests that a combination of spectral
width and shape may advance boundary layer identification by HF radar. For the
two December days studied the onset of radar cusp backscatter occurred within
pre-existing 630.0 nm cusp auroral activity and appear to be initiated by
sunrise, i.e. favourable radio wave propagation conditions had to develop.
Better methods are put forward for analysing optical data, and for physical
interpretation of HF radar data, and for combining these data, as applied to
detection, tracking, and better understanding of dayside aurora. The broader
motivation of this work is to develop wider use by the scientific community, of
results of these techniques, to accelerate understanding of dynamic
high-latitude boundary-processes. The contributions in this work are: (1)
improved techniques of analysis of observational data, yielding meaningfully
enhanced accuracy for deduced cusp locations; (2) a correspondingly more
pronounced validation of correlation of boundary locations derived from the
observational data set; and (3) a firmer physical rationale as to why the good
correlation observed should theoretically be expected.
Key words: Ionosphere (ionospheric irregularities;
polar ionosphere) |
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