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| Titel |
Deriving the normalised ion-neutral collision frequency from EISCAT observations |
| VerfasserIn |
J. A. Davies, Mark Lester, T. R. Robinson |
| 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 ; 15, no. 12 ; Nr. 15, no. 12, S.1557-1569 |
| Datensatznummer |
250013040
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| Publikation (Nr.) |
 copernicus.org/angeo-15-1557-1997.pdf |
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| Zusammenfassung |
| Common programme observations by the EISCAT
UHF radar revealed an extended interval, post geomagnetic local noon on 03 April
1992, during which the F-region ion velocity orthogonal to the geomagnetic field
was significantly enhanced, to values exceeding 2 km s–1
corresponding to a perpendicular electric field of some 100 mV m–1.
Observations from this interval are used to illustrate a method by which
estimates of the E-region ion-neutral collision frequency may be derived in the
presence of enhanced electric field. From both the rotation of the ion velocity
vector and the reduction in the ion velocity magnitude relative to that in the
F-region, independent estimates of the normalised ion-neutral collision
frequency are made at the UHF E-region tristatic altitudes; the derived values
are, in general, lower than model predictions. Although initial calculations
assume a stationary neutral atmosphere, first-order estimates of the E-region
neutral wind are subsequently employed to calculate revised estimates of the
normalised ion-neutral collision frequency; these neutral winds are derived by
attributing the difference between predicted and observed enhancements in
field-parallel ion temperature to thermospheric motion. The inclusion of neutral
winds, which are themselves not inconsiderable, appears to have only a limited
effect on the normalised collision frequencies derived. |
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