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Title: On the collocation between dayside auroral activity and coherent HF radar backscatter
Authors: Moen, J.
Carlson, H. C.
Milan, Stephen E.
Shumilov, N.
Lybekk, B.
Sandholt, P. E.
Lester, Mark
First Published: 1-Jan-2001
Publisher: European Geosciences Union (EGU), Copernicus Publications, Springer Verlag (Germany)
Abstract: 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.
DOI Link: 10.1007/s005850000302
ISSN: 0992-7689
eISSN: 1432-0576
Type: Journal Article
Rights: Archived with reference to SHERPA/RoMEO and publisher website. © European Geosciences Union 2000. Version of record:
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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