Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations
We analyse a conjunction event of the Cluster II spacecraft with the MIRACLE ground-based instrument net-work in northern Fennoscandia on 6 February 2001, between 23:00 and 00:00 UT. Shortly after the spacecraft were located at perigee, the Cluster II satellites’ magnetic footpoints move northwards...
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ftdoajarticles:oai:doaj.org/article:0cf3351794c349b681aa0a357fcba2ef 2023-05-15T16:12:18+02:00 Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations O. Amm A. Aikio J.-M. Bosqued M. Dunlop A. Fazakerley P. Janhunen K. Kauristie M. Lester I. Sillanpää M. G. G. T. Taylor A. Vontrat-Reberac K. Mursula M. André 2003-08-01T00:00:00Z https://doi.org/10.5194/angeo-21-1737-2003 https://doaj.org/article/0cf3351794c349b681aa0a357fcba2ef EN eng Copernicus Publications https://www.ann-geophys.net/21/1737/2003/angeo-21-1737-2003.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-21-1737-2003 0992-7689 1432-0576 https://doaj.org/article/0cf3351794c349b681aa0a357fcba2ef Annales Geophysicae, Vol 21, Pp 1737-1751 (2003) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2003 ftdoajarticles https://doi.org/10.5194/angeo-21-1737-2003 2022-12-31T15:55:18Z We analyse a conjunction event of the Cluster II spacecraft with the MIRACLE ground-based instrument net-work in northern Fennoscandia on 6 February 2001, between 23:00 and 00:00 UT. Shortly after the spacecraft were located at perigee, the Cluster II satellites’ magnetic footpoints move northwards over Scandinavia and Svalbard, almost perfectly aligned with the central chain of the IMAGE magnetometer network, and cross a morning sector ionospheric shear zone during this passage. In this study we focus on the mesoscale structure of the ionosphere. Ionospheric conductances, true horizontal currents, and field-aligned currents (FAC) are calculated from the ground-based measurements of the IMAGE magnetometers and the STARE coherent scatter radar, using the 1-D method of characteristics. An excellent agreement between these results and the FAC observed by Cluster II is reached after averaging the Cluster measurements to mesoscales, as well as between the location of the convection reversal boundary (CRB), as observed by STARE and by the Cluster II EFW instrument. A sheet of downward FAC is observed in the vicinity of the CRB, which is mainly caused by the positive divergence of the electric field there. This FAC sheet is detached by 0.5°–2° of latitude from a more equatorward downward FAC sheet at the poleward flank of the westward electrojet. This latter FAC sheet, as well as the upward FAC at the equatorward flank of the jet, are mainly caused by meridional gradients in the ionospheric conductances, which reach up to 25 S in the electrojet region, but only ~ 5 S poleward of it, with a minimum at the CRB. Particle measurements show that the major part of the downward FAC is carried by upward flowing electrons, and only a small part by downward flowing ions. The open-closed field line boundary is found to be located 3°–4° poleward of the CRB, implying significant errors if the latter is used as a proxy of the former. Key words. Ionosphere (electric fields and currents) – Magnetosphere physics (current systems; ... Article in Journal/Newspaper Fennoscandia Svalbard Directory of Open Access Journals: DOAJ Articles Svalbard Annales Geophysicae 21 8 1737 1751 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 O. Amm A. Aikio J.-M. Bosqued M. Dunlop A. Fazakerley P. Janhunen K. Kauristie M. Lester I. Sillanpää M. G. G. T. Taylor A. Vontrat-Reberac K. Mursula M. André Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
We analyse a conjunction event of the Cluster II spacecraft with the MIRACLE ground-based instrument net-work in northern Fennoscandia on 6 February 2001, between 23:00 and 00:00 UT. Shortly after the spacecraft were located at perigee, the Cluster II satellites’ magnetic footpoints move northwards over Scandinavia and Svalbard, almost perfectly aligned with the central chain of the IMAGE magnetometer network, and cross a morning sector ionospheric shear zone during this passage. In this study we focus on the mesoscale structure of the ionosphere. Ionospheric conductances, true horizontal currents, and field-aligned currents (FAC) are calculated from the ground-based measurements of the IMAGE magnetometers and the STARE coherent scatter radar, using the 1-D method of characteristics. An excellent agreement between these results and the FAC observed by Cluster II is reached after averaging the Cluster measurements to mesoscales, as well as between the location of the convection reversal boundary (CRB), as observed by STARE and by the Cluster II EFW instrument. A sheet of downward FAC is observed in the vicinity of the CRB, which is mainly caused by the positive divergence of the electric field there. This FAC sheet is detached by 0.5°–2° of latitude from a more equatorward downward FAC sheet at the poleward flank of the westward electrojet. This latter FAC sheet, as well as the upward FAC at the equatorward flank of the jet, are mainly caused by meridional gradients in the ionospheric conductances, which reach up to 25 S in the electrojet region, but only ~ 5 S poleward of it, with a minimum at the CRB. Particle measurements show that the major part of the downward FAC is carried by upward flowing electrons, and only a small part by downward flowing ions. The open-closed field line boundary is found to be located 3°–4° poleward of the CRB, implying significant errors if the latter is used as a proxy of the former. Key words. Ionosphere (electric fields and currents) – Magnetosphere physics (current systems; ... |
format |
Article in Journal/Newspaper |
author |
O. Amm A. Aikio J.-M. Bosqued M. Dunlop A. Fazakerley P. Janhunen K. Kauristie M. Lester I. Sillanpää M. G. G. T. Taylor A. Vontrat-Reberac K. Mursula M. André |
author_facet |
O. Amm A. Aikio J.-M. Bosqued M. Dunlop A. Fazakerley P. Janhunen K. Kauristie M. Lester I. Sillanpää M. G. G. T. Taylor A. Vontrat-Reberac K. Mursula M. André |
author_sort |
O. Amm |
title |
Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations |
title_short |
Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations |
title_full |
Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations |
title_fullStr |
Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations |
title_full_unstemmed |
Mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate Cluster II and MIRACLE ground-based observations |
title_sort |
mesoscale structure of a morning sector ionospheric shear flow region determined by conjugate cluster ii and miracle ground-based observations |
publisher |
Copernicus Publications |
publishDate |
2003 |
url |
https://doi.org/10.5194/angeo-21-1737-2003 https://doaj.org/article/0cf3351794c349b681aa0a357fcba2ef |
geographic |
Svalbard |
geographic_facet |
Svalbard |
genre |
Fennoscandia Svalbard |
genre_facet |
Fennoscandia Svalbard |
op_source |
Annales Geophysicae, Vol 21, Pp 1737-1751 (2003) |
op_relation |
https://www.ann-geophys.net/21/1737/2003/angeo-21-1737-2003.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-21-1737-2003 0992-7689 1432-0576 https://doaj.org/article/0cf3351794c349b681aa0a357fcba2ef |
op_doi |
https://doi.org/10.5194/angeo-21-1737-2003 |
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Annales Geophysicae |
container_volume |
21 |
container_issue |
8 |
container_start_page |
1737 |
op_container_end_page |
1751 |
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