HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring
Three intervals of polar patch formation, as observed by the CUTLASS Finland HF coherent radar, are presented. Simultaneous observations from a vertical ionosonde located at Longyearbyen on Svalbard, situated in the dayside convection throat region, allow for F-region plasma structuring, leading to...
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Online Access: | https://doi.org/10.5194/angeo-20-487-2002 https://angeo.copernicus.org/articles/20/487/2002/ |
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ftcopernicus:oai:publications.copernicus.org:angeo34792 2023-05-15T17:08:30+02:00 HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring Milan, S. E. Lester, M. Yeoman, T. K. 2018-09-27 application/pdf https://doi.org/10.5194/angeo-20-487-2002 https://angeo.copernicus.org/articles/20/487/2002/ eng eng doi:10.5194/angeo-20-487-2002 https://angeo.copernicus.org/articles/20/487/2002/ eISSN: 1432-0576 Text 2018 ftcopernicus https://doi.org/10.5194/angeo-20-487-2002 2020-07-20T16:27:50Z Three intervals of polar patch formation, as observed by the CUTLASS Finland HF coherent radar, are presented. Simultaneous observations from a vertical ionosonde located at Longyearbyen on Svalbard, situated in the dayside convection throat region, allow for F-region plasma structuring, leading to polar cap patch formation to be determined. Solar wind and interplanetary magnetic field (IMF) precursors of polar patch formation are investigated with MFI and SWE measurements from the Wind spacecraft. We find that in the cases studied polar cap patches are formed in response to changes in the orientation of the IMF, especially in the By component. The resultant changes in the dayside convection pattern alter the source of plasma drifting through the convection throat region into the polar cap. When the convection flow is directed predominantly polewards, high density sub-auroral or mid-latitude plasma enters the polar cap; when flow is directed zonally, low density plasma entrained in the convection return flow replaces it. This mechanism can act to significantly structure the plasma density at sub-auroral or mid-latitudes as well as in the polar cap. In winter months, polar patches appear to be produced by depletions in an otherwise high plasma density tongue of ionisation. In summer months, patches are enhancements of an otherwise low density tongue of ionisation. Key words. Ionosphere (ionospheric irregularities; plasma convection; polar ionosphere) Text Longyearbyen Svalbard Copernicus Publications: E-Journals Longyearbyen Svalbard Annales Geophysicae 20 4 487 499 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Three intervals of polar patch formation, as observed by the CUTLASS Finland HF coherent radar, are presented. Simultaneous observations from a vertical ionosonde located at Longyearbyen on Svalbard, situated in the dayside convection throat region, allow for F-region plasma structuring, leading to polar cap patch formation to be determined. Solar wind and interplanetary magnetic field (IMF) precursors of polar patch formation are investigated with MFI and SWE measurements from the Wind spacecraft. We find that in the cases studied polar cap patches are formed in response to changes in the orientation of the IMF, especially in the By component. The resultant changes in the dayside convection pattern alter the source of plasma drifting through the convection throat region into the polar cap. When the convection flow is directed predominantly polewards, high density sub-auroral or mid-latitude plasma enters the polar cap; when flow is directed zonally, low density plasma entrained in the convection return flow replaces it. This mechanism can act to significantly structure the plasma density at sub-auroral or mid-latitudes as well as in the polar cap. In winter months, polar patches appear to be produced by depletions in an otherwise high plasma density tongue of ionisation. In summer months, patches are enhancements of an otherwise low density tongue of ionisation. Key words. Ionosphere (ionospheric irregularities; plasma convection; polar ionosphere) |
format |
Text |
author |
Milan, S. E. Lester, M. Yeoman, T. K. |
spellingShingle |
Milan, S. E. Lester, M. Yeoman, T. K. HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
author_facet |
Milan, S. E. Lester, M. Yeoman, T. K. |
author_sort |
Milan, S. E. |
title |
HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
title_short |
HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
title_full |
HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
title_fullStr |
HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
title_full_unstemmed |
HF radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
title_sort |
hf radar polar patch formation revisited: summer and winter variations in dayside plasma structuring |
publishDate |
2018 |
url |
https://doi.org/10.5194/angeo-20-487-2002 https://angeo.copernicus.org/articles/20/487/2002/ |
geographic |
Longyearbyen Svalbard |
geographic_facet |
Longyearbyen Svalbard |
genre |
Longyearbyen Svalbard |
genre_facet |
Longyearbyen Svalbard |
op_source |
eISSN: 1432-0576 |
op_relation |
doi:10.5194/angeo-20-487-2002 https://angeo.copernicus.org/articles/20/487/2002/ |
op_doi |
https://doi.org/10.5194/angeo-20-487-2002 |
container_title |
Annales Geophysicae |
container_volume |
20 |
container_issue |
4 |
container_start_page |
487 |
op_container_end_page |
499 |
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1766064274953732096 |