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| Titel |
HF radar observations of high-aspect angle backscatter from the E-region |
| VerfasserIn |
S. E. Milan, Mark Lester, T. K. Yeoman, T. R. Robinson, M. V. Uspensky, J.-P. Villain |
| 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 ; 22, no. 3 ; Nr. 22, no. 3 (2004-03-19), S.829-847 |
| Datensatznummer |
250014805
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| Publikation (Nr.) |
 copernicus.org/angeo-22-829-2004.pdf |
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| Zusammenfassung |
We present evidence for the observation of high-aspect
angle HF radar backscatter from the auroral electrojets, and describe the
spectral characteristics of these echoes. Such backscatter is observed at
very near ranges where ionospheric refraction is not sufficient to bring the
sounding radio waves to orthogonality with the magnetic field; the frequency
dependence of this propagation effect is investigated with the Stereo
upgrade of the CUTLASS Iceland radar. We term the occurrence of such echoes
the "high-aspect angle irregularity region" or HAIR. It is suggested that
backscatter is observed at aspect angles as high as 30°, with an aspect
sensitivity as low as 1dB deg–1. These echoes are distinguished from
normal electrojet backscatter by having low Doppler shifts with an azimuthal
dependence that appears more consistent with the direction of the convection
electric field  than with the
expected electron  drift direction. This is
discussed in terms of the linear theory dispersion relation for electrojet
waves.
Key words. Ionosphere (ionospheric irregularities; plasma
waves and instabilities; auroral ionosphere) |
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