Deriving the normalised ion-neutral collision frequency from EISCAT observations
International audience 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...
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ftccsdartic:oai:HAL:hal-00316517v1 2023-11-12T04:16:36+01:00 Deriving the normalised ion-neutral collision frequency from EISCAT observations Davies, J. A. Lester, M. Robinson, T. R. Radio and Space Plasma Physics Group Leicester (RSPP) University of Leicester 1997 https://hal.science/hal-00316517 https://hal.science/hal-00316517/document https://hal.science/hal-00316517/file/angeo-15-1557-1997.pdf en eng HAL CCSD European Geosciences Union hal-00316517 https://hal.science/hal-00316517 https://hal.science/hal-00316517/document https://hal.science/hal-00316517/file/angeo-15-1557-1997.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316517 Annales Geophysicae, 1997, 15 (12), pp.1557-1569 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/article Journal articles 1997 ftccsdartic 2023-10-21T23:08:27Z International audience 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. Article in Journal/Newspaper EISCAT Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
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Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences Davies, J. A. Lester, M. Robinson, T. R. Deriving the normalised ion-neutral collision frequency from EISCAT observations |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience 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. |
author2 |
Radio and Space Plasma Physics Group Leicester (RSPP) University of Leicester |
format |
Article in Journal/Newspaper |
author |
Davies, J. A. Lester, M. Robinson, T. R. |
author_facet |
Davies, J. A. Lester, M. Robinson, T. R. |
author_sort |
Davies, J. A. |
title |
Deriving the normalised ion-neutral collision frequency from EISCAT observations |
title_short |
Deriving the normalised ion-neutral collision frequency from EISCAT observations |
title_full |
Deriving the normalised ion-neutral collision frequency from EISCAT observations |
title_fullStr |
Deriving the normalised ion-neutral collision frequency from EISCAT observations |
title_full_unstemmed |
Deriving the normalised ion-neutral collision frequency from EISCAT observations |
title_sort |
deriving the normalised ion-neutral collision frequency from eiscat observations |
publisher |
HAL CCSD |
publishDate |
1997 |
url |
https://hal.science/hal-00316517 https://hal.science/hal-00316517/document https://hal.science/hal-00316517/file/angeo-15-1557-1997.pdf |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316517 Annales Geophysicae, 1997, 15 (12), pp.1557-1569 |
op_relation |
hal-00316517 https://hal.science/hal-00316517 https://hal.science/hal-00316517/document https://hal.science/hal-00316517/file/angeo-15-1557-1997.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782333656994414592 |