Localized structure in the cusp and high-latitude ionosphere: a modelling study
International audience The ionospheric signature of a flux transfer event (FTE) seen in EISCAT radar data has been used as the basis for a modelling study using a new numerical model of the high-latitude ionosphere developed at the University of Sheffield, UK. The evolution of structure in the high-...
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ftinsu:oai:HAL:hal-00316567v1 2023-11-12T04:16:38+01:00 Localized structure in the cusp and high-latitude ionosphere: a modelling study Balmforth, H. F. Moffett, R. J. Rodger, A. S. Upper Atmosphere Modelling Group (UAMG) University of Sheffield Sheffield British Antarctic Survey (BAS) Natural Environment Research Council (NERC) 1999 https://hal.science/hal-00316567 https://hal.science/hal-00316567/document https://hal.science/hal-00316567/file/angeo-17-455-1999.pdf en eng HAL CCSD European Geosciences Union hal-00316567 https://hal.science/hal-00316567 https://hal.science/hal-00316567/document https://hal.science/hal-00316567/file/angeo-17-455-1999.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316567 Annales Geophysicae, 1999, 17 (4), pp.455-462 [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 1999 ftinsu 2023-10-25T16:25:34Z International audience The ionospheric signature of a flux transfer event (FTE) seen in EISCAT radar data has been used as the basis for a modelling study using a new numerical model of the high-latitude ionosphere developed at the University of Sheffield, UK. The evolution of structure in the high-latitude ionosphere is investigated and examined with respect to the current views of polar patch formation and development. A localized velocity enhancement, of the type associated with FTEs, is added to the plasma as it passes through the cusp. This is found to produce a region of greatly enhanced ion temperature. The new model can provide greater detail during this event as it includes anisotropic temperature calculations for the O + ions. This illustrates the uneven partitioning of the energy during an event of this type. O + ion temperatures are found to become increasingly anisotropic, with the perpendicular temperature being substantially larger than the parallel component during the velocity enhancement. The enhanced temperatures lead to an increase in the recombination rate, which results in an alteration of the ion concentrations. A region of decreased O + and increased molecular ion concentration develops in the cusp. The electron temperature is less enhanced than the ions. As the new model has an upper boundary of 10 000 km the topside can also be studied in great detail. Large upward fluxes are seen to transport plasma to higher altitudes, contributing to the alteration of the ion densities. Plasma is stored in the topside ionosphere and released several hours after the FTE has finished as the flux tube convects across the polar cap. This mechanism illustrates how concentration patches can be created on the dayside and be maintained into the nightside polar cap. Article in Journal/Newspaper EISCAT Institut national des sciences de l'Univers: HAL-INSU Sheffield |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
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 Balmforth, H. F. Moffett, R. J. Rodger, A. S. Localized structure in the cusp and high-latitude ionosphere: a modelling study |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience The ionospheric signature of a flux transfer event (FTE) seen in EISCAT radar data has been used as the basis for a modelling study using a new numerical model of the high-latitude ionosphere developed at the University of Sheffield, UK. The evolution of structure in the high-latitude ionosphere is investigated and examined with respect to the current views of polar patch formation and development. A localized velocity enhancement, of the type associated with FTEs, is added to the plasma as it passes through the cusp. This is found to produce a region of greatly enhanced ion temperature. The new model can provide greater detail during this event as it includes anisotropic temperature calculations for the O + ions. This illustrates the uneven partitioning of the energy during an event of this type. O + ion temperatures are found to become increasingly anisotropic, with the perpendicular temperature being substantially larger than the parallel component during the velocity enhancement. The enhanced temperatures lead to an increase in the recombination rate, which results in an alteration of the ion concentrations. A region of decreased O + and increased molecular ion concentration develops in the cusp. The electron temperature is less enhanced than the ions. As the new model has an upper boundary of 10 000 km the topside can also be studied in great detail. Large upward fluxes are seen to transport plasma to higher altitudes, contributing to the alteration of the ion densities. Plasma is stored in the topside ionosphere and released several hours after the FTE has finished as the flux tube convects across the polar cap. This mechanism illustrates how concentration patches can be created on the dayside and be maintained into the nightside polar cap. |
author2 |
Upper Atmosphere Modelling Group (UAMG) University of Sheffield Sheffield British Antarctic Survey (BAS) Natural Environment Research Council (NERC) |
format |
Article in Journal/Newspaper |
author |
Balmforth, H. F. Moffett, R. J. Rodger, A. S. |
author_facet |
Balmforth, H. F. Moffett, R. J. Rodger, A. S. |
author_sort |
Balmforth, H. F. |
title |
Localized structure in the cusp and high-latitude ionosphere: a modelling study |
title_short |
Localized structure in the cusp and high-latitude ionosphere: a modelling study |
title_full |
Localized structure in the cusp and high-latitude ionosphere: a modelling study |
title_fullStr |
Localized structure in the cusp and high-latitude ionosphere: a modelling study |
title_full_unstemmed |
Localized structure in the cusp and high-latitude ionosphere: a modelling study |
title_sort |
localized structure in the cusp and high-latitude ionosphere: a modelling study |
publisher |
HAL CCSD |
publishDate |
1999 |
url |
https://hal.science/hal-00316567 https://hal.science/hal-00316567/document https://hal.science/hal-00316567/file/angeo-17-455-1999.pdf |
geographic |
Sheffield |
geographic_facet |
Sheffield |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316567 Annales Geophysicae, 1999, 17 (4), pp.455-462 |
op_relation |
hal-00316567 https://hal.science/hal-00316567 https://hal.science/hal-00316567/document https://hal.science/hal-00316567/file/angeo-17-455-1999.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782333714735300608 |