Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study
International audience The dynamics of the cusp region and post-noon sector for an interval of predominantly IMF B y , B z < 0 nT are studied with the CUTLASS Finland coherent HF radar, a meridian-scanning photometer located at Ny Ålesund, Svalbard, and a meridional network of magnetometers. The...
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ftinsu:oai:HAL:hal-00316523v1 2023-11-12T04:23:34+01:00 Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study Milan, S. E. Lester, M. Cowley, S. W. H. Moen, J. Sandholt, P. E. Owen, C. J. Department of Physics and Astronomy Leicester University of Leicester UNIS UniS Department of Physics Oslo Faculty of Mathematics and Natural Sciences Oslo University of Oslo (UiO)-University of Oslo (UiO) Queen Mary and Westfield College Queen Mary University of London (QMUL) 1999 https://hal.science/hal-00316523 https://hal.science/hal-00316523/document https://hal.science/hal-00316523/file/angeo-17-159-1999.pdf en eng HAL CCSD European Geosciences Union hal-00316523 https://hal.science/hal-00316523 https://hal.science/hal-00316523/document https://hal.science/hal-00316523/file/angeo-17-159-1999.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316523 Annales Geophysicae, 1999, 17 (2), pp.159-172 [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 dynamics of the cusp region and post-noon sector for an interval of predominantly IMF B y , B z < 0 nT are studied with the CUTLASS Finland coherent HF radar, a meridian-scanning photometer located at Ny Ålesund, Svalbard, and a meridional network of magnetometers. The scanning mode of the radar is such that one beam is sampled every 14 s, and a 30° azimuthal sweep is completed every 2 minutes, all at 15 km range resolution. Both the radar backscatter and red line (630 nm) optical observations are closely co-located, especially at their equatorward boundary. The optical and radar aurora reveal three different behaviours which can interchange on the scale of minutes, and which are believed to be related to the dynamic nature of energy and momentum transfer from the solar wind to the magnetosphere through transient dayside reconnection. Two interpretations of the observations are presented, based upon the assumed location of the open/closed field line boundary (OCFLB). In the first, the OCFLB is co-located with equatorward boundary of the optical and radar aurora, placing most of the observations on open field lines. In the second, the observed aurora are interpreted as the ionospheric footprint of the region 1 current system, and the OCFLB is placed near the poleward edge of the radar backscatter and visible aurora; in this interpretation, most of the observations are placed on closed field lines, though transient brightenings of the optical aurora occur on open field lines. The observations reveal several transient features, including poleward and equatorward steps in the observed boundaries, "braiding" of the backscatter power, and 2 minute quasi-periodic enhancements of the plasma drift and optical intensity, predominantly on closed field lines. Article in Journal/Newspaper Ny Ålesund Ny-Ålesund Svalbard Institut national des sciences de l'Univers: HAL-INSU Ny-Ålesund Svalbard |
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 Milan, S. E. Lester, M. Cowley, S. W. H. Moen, J. Sandholt, P. E. Owen, C. J. Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case 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 dynamics of the cusp region and post-noon sector for an interval of predominantly IMF B y , B z < 0 nT are studied with the CUTLASS Finland coherent HF radar, a meridian-scanning photometer located at Ny Ålesund, Svalbard, and a meridional network of magnetometers. The scanning mode of the radar is such that one beam is sampled every 14 s, and a 30° azimuthal sweep is completed every 2 minutes, all at 15 km range resolution. Both the radar backscatter and red line (630 nm) optical observations are closely co-located, especially at their equatorward boundary. The optical and radar aurora reveal three different behaviours which can interchange on the scale of minutes, and which are believed to be related to the dynamic nature of energy and momentum transfer from the solar wind to the magnetosphere through transient dayside reconnection. Two interpretations of the observations are presented, based upon the assumed location of the open/closed field line boundary (OCFLB). In the first, the OCFLB is co-located with equatorward boundary of the optical and radar aurora, placing most of the observations on open field lines. In the second, the observed aurora are interpreted as the ionospheric footprint of the region 1 current system, and the OCFLB is placed near the poleward edge of the radar backscatter and visible aurora; in this interpretation, most of the observations are placed on closed field lines, though transient brightenings of the optical aurora occur on open field lines. The observations reveal several transient features, including poleward and equatorward steps in the observed boundaries, "braiding" of the backscatter power, and 2 minute quasi-periodic enhancements of the plasma drift and optical intensity, predominantly on closed field lines. |
author2 |
Department of Physics and Astronomy Leicester University of Leicester UNIS UniS Department of Physics Oslo Faculty of Mathematics and Natural Sciences Oslo University of Oslo (UiO)-University of Oslo (UiO) Queen Mary and Westfield College Queen Mary University of London (QMUL) |
format |
Article in Journal/Newspaper |
author |
Milan, S. E. Lester, M. Cowley, S. W. H. Moen, J. Sandholt, P. E. Owen, C. J. |
author_facet |
Milan, S. E. Lester, M. Cowley, S. W. H. Moen, J. Sandholt, P. E. Owen, C. J. |
author_sort |
Milan, S. E. |
title |
Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study |
title_short |
Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study |
title_full |
Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study |
title_fullStr |
Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study |
title_full_unstemmed |
Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study |
title_sort |
meridian-scanning photometer, coherent hf radar, and magnetometer observations of the cusp: a case study |
publisher |
HAL CCSD |
publishDate |
1999 |
url |
https://hal.science/hal-00316523 https://hal.science/hal-00316523/document https://hal.science/hal-00316523/file/angeo-17-159-1999.pdf |
geographic |
Ny-Ålesund Svalbard |
geographic_facet |
Ny-Ålesund Svalbard |
genre |
Ny Ålesund Ny-Ålesund Svalbard |
genre_facet |
Ny Ålesund Ny-Ålesund Svalbard |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316523 Annales Geophysicae, 1999, 17 (2), pp.159-172 |
op_relation |
hal-00316523 https://hal.science/hal-00316523 https://hal.science/hal-00316523/document https://hal.science/hal-00316523/file/angeo-17-159-1999.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782338285192871936 |