Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets
We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conduct...
Published in: | Annales Geophysicae |
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Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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Springer Verlag
1999
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00037014 2023-05-15T16:04:44+02:00 Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets Valladares, C. E. Alcaydé, D. Rodriguez, J. V. Ruohoniemi, J. M. Van Eyken, A. P. 1999-08 electronic https://doi.org/10.1007/s00585-999-1020-6 https://noa.gwlb.de/receive/cop_mods_00037014 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00036968/angeo-17-1020-1999.pdf https://angeo.copernicus.org/articles/17/1020/1999/angeo-17-1020-1999.pdf eng eng Springer Verlag Annales Geophysicae -- http://www.bibliothek.uni-regensburg.de/ezeit/?1458425 -- https://www.ann-geophys.net/ -- https://www.ann-geophys.net/volumes.html -- http://link.springer.com/journal/585 -- 1432-0576 https://doi.org/10.1007/s00585-999-1020-6 https://noa.gwlb.de/receive/cop_mods_00037014 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00036968/angeo-17-1020-1999.pdf https://angeo.copernicus.org/articles/17/1020/1999/angeo-17-1020-1999.pdf https://open-access.net/ uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 1999 ftnonlinearchiv https://doi.org/10.1007/s00585-999-1020-6 2022-02-08T22:43:43Z We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two different types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The first event consisted of the passage of traveling convection vortices (TCV). The other event occurred in association with the development of large plasma jets (LPJ) embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also confirmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O+ recombination due to an elevated Ti, which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km) longitudinal extension and were 200-300 km in width. They were seen principally with the Sondrestrom, and SuperDARN radars. Enhanced ion temperature (Ti) was also observed by the Sondrestrom and EISCAT radars. These channels of high Ti were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma flow is important to define the depth of the density depletion. Systematic changes in the latitudinal location and in the intensity of the LPJs were observed in the 2 min time resolution data of the SuperDARN radars. The effect of the abrupt changes in the LPJs location is to create regions containing dayside plasma almost detached from the rest of the oval density. One of these density features was seen by the Sondrestrom radar at 1542 UT. The data presented here suggest that two plasma structuring mechanisms (TCVs and LPJs) can act tens of minutes apart to produce higher levels of density structures in the near noon F-region ionosphere. Key words. Ionosphere (ionospheric irregularities) · Magnetospheric physics (electric fields; polar cap phenomena) Article in Journal/Newspaper EISCAT Greenland Niedersächsisches Online-Archiv NOA Greenland Annales Geophysicae 17 8 1020 1039 |
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Open Polar |
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Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Valladares, C. E. Alcaydé, D. Rodriguez, J. V. Ruohoniemi, J. M. Van Eyken, A. P. Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
topic_facet |
article Verlagsveröffentlichung |
description |
We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two different types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The first event consisted of the passage of traveling convection vortices (TCV). The other event occurred in association with the development of large plasma jets (LPJ) embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also confirmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O+ recombination due to an elevated Ti, which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km) longitudinal extension and were 200-300 km in width. They were seen principally with the Sondrestrom, and SuperDARN radars. Enhanced ion temperature (Ti) was also observed by the Sondrestrom and EISCAT radars. These channels of high Ti were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma flow is important to define the depth of the density depletion. Systematic changes in the latitudinal location and in the intensity of the LPJs were observed in the 2 min time resolution data of the SuperDARN radars. The effect of the abrupt changes in the LPJs location is to create regions containing dayside plasma almost detached from the rest of the oval density. One of these density features was seen by the Sondrestrom radar at 1542 UT. The data presented here suggest that two plasma structuring mechanisms (TCVs and LPJs) can act tens of minutes apart to produce higher levels of density structures in the near noon F-region ionosphere. Key words. Ionosphere (ionospheric irregularities) · Magnetospheric physics (electric fields; polar cap phenomena) |
format |
Article in Journal/Newspaper |
author |
Valladares, C. E. Alcaydé, D. Rodriguez, J. V. Ruohoniemi, J. M. Van Eyken, A. P. |
author_facet |
Valladares, C. E. Alcaydé, D. Rodriguez, J. V. Ruohoniemi, J. M. Van Eyken, A. P. |
author_sort |
Valladares, C. E. |
title |
Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
title_short |
Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
title_full |
Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
title_fullStr |
Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
title_full_unstemmed |
Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
title_sort |
observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets |
publisher |
Springer Verlag |
publishDate |
1999 |
url |
https://doi.org/10.1007/s00585-999-1020-6 https://noa.gwlb.de/receive/cop_mods_00037014 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00036968/angeo-17-1020-1999.pdf https://angeo.copernicus.org/articles/17/1020/1999/angeo-17-1020-1999.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
EISCAT Greenland |
genre_facet |
EISCAT Greenland |
op_relation |
Annales Geophysicae -- http://www.bibliothek.uni-regensburg.de/ezeit/?1458425 -- https://www.ann-geophys.net/ -- https://www.ann-geophys.net/volumes.html -- http://link.springer.com/journal/585 -- 1432-0576 https://doi.org/10.1007/s00585-999-1020-6 https://noa.gwlb.de/receive/cop_mods_00037014 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00036968/angeo-17-1020-1999.pdf https://angeo.copernicus.org/articles/17/1020/1999/angeo-17-1020-1999.pdf |
op_rights |
https://open-access.net/ uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1007/s00585-999-1020-6 |
container_title |
Annales Geophysicae |
container_volume |
17 |
container_issue |
8 |
container_start_page |
1020 |
op_container_end_page |
1039 |
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1766400360551809024 |