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| Titel |
The relationship between VHF radar auroral backscatter amplitude and Doppler velocity: a statistical study |
| VerfasserIn |
B. A. Shand, Mark Lester, T. K. Yeoman |
| 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 ; 14, no. 8 ; Nr. 14, no. 8, S.803-810 |
| Datensatznummer |
250012383
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| Publikation (Nr.) |
 copernicus.org/angeo-14-803-1996.pdf |
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| Zusammenfassung |
| A statistical investigation of the
relationship between VHF radar auroral backscatter intensity and Doppler
velocity has been undertaken with data collected from 8 years operation of the
Wick site of the Sweden And Britain Radar-auroral Experiment (SABRE). The
results indicate three different regimes within the statistical data set;
firstly, for Doppler velocities <200 m s–1, the backscatter
intensity (measured in decibels) remains relatively constant. Secondly, a linear
relationship is observed between the backscatter intensity (in decibels) and
Doppler velocity for velocities between 200 m s–1 and 700 m s–1.
At velocities greater than 700 m s–1 the backscatter intensity
saturates at a maximum value as the Doppler velocity increases. There are three
possible geophysical mechanisms for the saturation in the backscatter intensity
at high phase speeds: a saturation in the irregularity turbulence level, a
maximisation of the scattering volume, and a modification of the local ambient
electron density. There is also a difference in the dependence of the
backscatter intensity on Doppler velocity for the flow towards and away from the
radar. The results for flow towards the radar exhibit a consistent relationship
between backscatter intensity and measured velocities throughout the solar
cycle. For flow away from the radar, however, the relationship between
backscatter intensity and Doppler velocity varies during the solar cycle. The
geometry of the SABRE system ensures that flow towards the radar is
predominantly associated with the eastward electrojet, and flow away is
associated with the westward electrojet. The difference in the backscatter
intensity variation as a function of Doppler velocity is attributed to
asymmetries between the eastward and westward electrojets and the geophysical
parameters controlling the backscatter amplitude. |
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