Observations of nightside auroral plasma upflows in the F-region and topside ionosphere
International audience Observations from the special UK EISCAT program UFIS are presented. UFIS is a joint UHF-VHF experiment, designed to make simultaneous measurements of enhanced vertical plasma flows in the F-region and topside ionospheres. Three distinct intervals of upward ion flow were observ...
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ftccsdartic:oai:HAL:hal-00316248v1 2023-11-12T04:16:38+01:00 Observations of nightside auroral plasma upflows in the F-region and topside ionosphere Foster, C. Lester, M. Radio and Space Plasma Physics Group Leicester (RSPP) University of Leicester 1996 https://hal.science/hal-00316248 https://hal.science/hal-00316248/document https://hal.science/hal-00316248/file/angeo-14-1274-1996.pdf en eng HAL CCSD European Geosciences Union hal-00316248 https://hal.science/hal-00316248 https://hal.science/hal-00316248/document https://hal.science/hal-00316248/file/angeo-14-1274-1996.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316248 Annales Geophysicae, 1996, 14 (12), pp.1274-1283 [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 1996 ftccsdartic 2023-10-21T23:08:39Z International audience Observations from the special UK EISCAT program UFIS are presented. UFIS is a joint UHF-VHF experiment, designed to make simultaneous measurements of enhanced vertical plasma flows in the F-region and topside ionospheres. Three distinct intervals of upward ion flow were observed. During the first event, upward ion fluxes in excess of 10 13 m ?2 s ?1 were detected, with vertical ion velocities reaching 300 m s ?1 at 800 km. The upflow was associated with the passage of an auroral arc through the radar field of view. In the F-region, an enhanced and sheared convection electric field on the leading edge of the arc resulted in heating of the ions, whilst at higher altitudes, above the precipitation region, strongly enhanced electron temperatures were observed; such features are commonly associated with the generation of plasma upflows. These observations demonstrate some of the acceleration mechanisms which can exist within the small-scale structure of an auroral arc. A later upflow event was associated with enhanced electron temperatures and only a moderate convection electric field, with no indication of significantly elevated ion tem- peratures. There was again some evidence of F-region particle precipitation at the time of the upflow, which exhibited vertical ion velocities of similar magnitude to the earlier upflow, suggesting that the behaviour of the electrons might be the dominant factor in this type of event. A third upflow was detected at altitudes above the observing range of the UHF radar, but which was evident in the VHF data from 600 km upwards. Smaller vertical velocities were observed in this event, which was apparently uncorrelated with any features observed at lower altitudes. Limitations imposed by the experimental conditions inhibit the interpretation of this event, although the upflow was again likely related to topside plasma heating. Article in Journal/Newspaper EISCAT Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
institution |
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 Foster, C. Lester, M. Observations of nightside auroral plasma upflows in the F-region and topside ionosphere |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience Observations from the special UK EISCAT program UFIS are presented. UFIS is a joint UHF-VHF experiment, designed to make simultaneous measurements of enhanced vertical plasma flows in the F-region and topside ionospheres. Three distinct intervals of upward ion flow were observed. During the first event, upward ion fluxes in excess of 10 13 m ?2 s ?1 were detected, with vertical ion velocities reaching 300 m s ?1 at 800 km. The upflow was associated with the passage of an auroral arc through the radar field of view. In the F-region, an enhanced and sheared convection electric field on the leading edge of the arc resulted in heating of the ions, whilst at higher altitudes, above the precipitation region, strongly enhanced electron temperatures were observed; such features are commonly associated with the generation of plasma upflows. These observations demonstrate some of the acceleration mechanisms which can exist within the small-scale structure of an auroral arc. A later upflow event was associated with enhanced electron temperatures and only a moderate convection electric field, with no indication of significantly elevated ion tem- peratures. There was again some evidence of F-region particle precipitation at the time of the upflow, which exhibited vertical ion velocities of similar magnitude to the earlier upflow, suggesting that the behaviour of the electrons might be the dominant factor in this type of event. A third upflow was detected at altitudes above the observing range of the UHF radar, but which was evident in the VHF data from 600 km upwards. Smaller vertical velocities were observed in this event, which was apparently uncorrelated with any features observed at lower altitudes. Limitations imposed by the experimental conditions inhibit the interpretation of this event, although the upflow was again likely related to topside plasma heating. |
author2 |
Radio and Space Plasma Physics Group Leicester (RSPP) University of Leicester |
format |
Article in Journal/Newspaper |
author |
Foster, C. Lester, M. |
author_facet |
Foster, C. Lester, M. |
author_sort |
Foster, C. |
title |
Observations of nightside auroral plasma upflows in the F-region and topside ionosphere |
title_short |
Observations of nightside auroral plasma upflows in the F-region and topside ionosphere |
title_full |
Observations of nightside auroral plasma upflows in the F-region and topside ionosphere |
title_fullStr |
Observations of nightside auroral plasma upflows in the F-region and topside ionosphere |
title_full_unstemmed |
Observations of nightside auroral plasma upflows in the F-region and topside ionosphere |
title_sort |
observations of nightside auroral plasma upflows in the f-region and topside ionosphere |
publisher |
HAL CCSD |
publishDate |
1996 |
url |
https://hal.science/hal-00316248 https://hal.science/hal-00316248/document https://hal.science/hal-00316248/file/angeo-14-1274-1996.pdf |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316248 Annales Geophysicae, 1996, 14 (12), pp.1274-1283 |
op_relation |
hal-00316248 https://hal.science/hal-00316248 https://hal.science/hal-00316248/document https://hal.science/hal-00316248/file/angeo-14-1274-1996.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782333714939772928 |