Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann
Abstract. 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 perpendi...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.497.6713 2023-05-15T16:04:34+02:00 Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann J. A. Davies M. Lester T. R. Robinson The Pennsylvania State University CiteSeerX Archives 1997 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.497.6713 http://www.ann-geophys.net/15/1557/1997/angeo-15-1557-1997.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.497.6713 http://www.ann-geophys.net/15/1557/1997/angeo-15-1557-1997.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.ann-geophys.net/15/1557/1997/angeo-15-1557-1997.pdf text 1997 ftciteseerx 2016-01-08T08:52:04Z Abstract. 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 atmo-sphere, 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 dierence 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 eect on the normalised collision frequencies derived. 1 Text EISCAT Unknown |
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ftciteseerx |
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English |
description |
Abstract. 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 atmo-sphere, 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 dierence 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 eect on the normalised collision frequencies derived. 1 |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
J. A. Davies M. Lester T. R. Robinson |
spellingShingle |
J. A. Davies M. Lester T. R. Robinson Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann |
author_facet |
J. A. Davies M. Lester T. R. Robinson |
author_sort |
J. A. Davies |
title |
Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann |
title_short |
Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann |
title_full |
Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann |
title_fullStr |
Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann |
title_full_unstemmed |
Deriving the normalised ion-neutral collision frequency from EISCAT observations, Ann |
title_sort |
deriving the normalised ion-neutral collision frequency from eiscat observations, ann |
publishDate |
1997 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.497.6713 http://www.ann-geophys.net/15/1557/1997/angeo-15-1557-1997.pdf |
genre |
EISCAT |
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EISCAT |
op_source |
http://www.ann-geophys.net/15/1557/1997/angeo-15-1557-1997.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.497.6713 http://www.ann-geophys.net/15/1557/1997/angeo-15-1557-1997.pdf |
op_rights |
Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
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1766400164193370112 |