EISCAT observations of unusual flows in the morning sector associated with weak substorm activity
Abstract. A discussion is given of plasma flows in the dawn and nightside high-latitude ionospheric regions during substorms occurring on a contracted auroral oval, as observed using the EISCAT CP-4-A experiment. Supporting data from the PACE radar, Greenland magnetometer chain, SAMNET magnetometers...
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Language: | English |
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SPRINGER VERLAG
2012
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Online Access: | http://hdl.handle.net/2381/19558 http://www.ann-geophys.net/12/541/1994/angeo-12-541-1994.html https://doi.org/10.1007/s00585-994-0541-2 |
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ftleicester:oai:lra.le.ac.uk:2381/19558 2023-05-15T16:04:28+02:00 EISCAT observations of unusual flows in the morning sector associated with weak substorm activity Fox, N. J. Lockwood, M. Cowley, S. W. H. Freeman, M. P. Friischristensen, E. Milling, D. K. Pinnock, M. Reeves, G. D. 2012-10-24T09:07:22Z metadata http://hdl.handle.net/2381/19558 http://www.ann-geophys.net/12/541/1994/angeo-12-541-1994.html https://doi.org/10.1007/s00585-994-0541-2 English eng SPRINGER VERLAG ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES, 1994, 12 (6), pp. 541-553 0992-7689 http://hdl.handle.net/2381/19558 http://www.ann-geophys.net/12/541/1994/angeo-12-541-1994.html doi:10.1007/s00585-994-0541-2 Copyright © European Geosciences Union 1994 Web of Science http://webofknowledge.com Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD HIGH-LATITUDE IONOSPHERE ENERGETIC PARTICLE MEASUREMENTS NORTH-SOUTH COMPONENT POLAR-CAP BOUNDARY GEOMAGNETIC-ACTIVITY PLASMA-FLOW AMPTE-UKS CONVECTION MAGNETOSPHERE Journal Article 2012 ftleicester https://doi.org/10.1007/s00585-994-0541-2 2019-03-22T20:16:58Z Abstract. A discussion is given of plasma flows in the dawn and nightside high-latitude ionospheric regions during substorms occurring on a contracted auroral oval, as observed using the EISCAT CP-4-A experiment. Supporting data from the PACE radar, Greenland magnetometer chain, SAMNET magnetometers and geostationary satellites are compared to the EISCAT observations. On 4 October 1989 a weak substorm with initial expansion phase onset signatures at 0030 UT, resulted in the convection reversal boundary observed by EISCAT (at ~0415 MLT) contracting rapidly poleward, causing a band of elevated ionospheric ion temperatures and a localised plasma density depletion. This polar cap contraction event is shown to be associated with various substorm signatures; Pi2 pulsations at mid-latitudes, magnetic bays in the midnight sector and particle injections at geosynchronous orbit. A similar event was observed on the following day around 0230 UT (~0515 MLT) with the unusual and significant difference that two convection reversals were observed, both contracting poleward. We show that this feature is not an ionospheric signature of two active reconnection neutral lines as predicted by the near-Earth neutral model before the plasmoid is "pinched off", and present two alternative explanations in terms of (1) viscous and lobe circulation cells and (2) polar cap contraction during northward IMF. The voltage associated with the anti-sunward flow between the reversals reaches a maximum of 13 kV during the substorm expansion phase. This suggests it to be associated with the polar cap contraction and caused by the reconnection of open flux in the geomagnetic tail which has mimicked "viscous-like" momentum transfer across the magnetopause. 45149 Article in Journal/Newspaper EISCAT Greenland University of Leicester: Leicester Research Archive (LRA) Greenland Annales Geophysicae 12 6 541 553 |
institution |
Open Polar |
collection |
University of Leicester: Leicester Research Archive (LRA) |
op_collection_id |
ftleicester |
language |
English |
topic |
Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD HIGH-LATITUDE IONOSPHERE ENERGETIC PARTICLE MEASUREMENTS NORTH-SOUTH COMPONENT POLAR-CAP BOUNDARY GEOMAGNETIC-ACTIVITY PLASMA-FLOW AMPTE-UKS CONVECTION MAGNETOSPHERE |
spellingShingle |
Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD HIGH-LATITUDE IONOSPHERE ENERGETIC PARTICLE MEASUREMENTS NORTH-SOUTH COMPONENT POLAR-CAP BOUNDARY GEOMAGNETIC-ACTIVITY PLASMA-FLOW AMPTE-UKS CONVECTION MAGNETOSPHERE Fox, N. J. Lockwood, M. Cowley, S. W. H. Freeman, M. P. Friischristensen, E. Milling, D. K. Pinnock, M. Reeves, G. D. EISCAT observations of unusual flows in the morning sector associated with weak substorm activity |
topic_facet |
Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD HIGH-LATITUDE IONOSPHERE ENERGETIC PARTICLE MEASUREMENTS NORTH-SOUTH COMPONENT POLAR-CAP BOUNDARY GEOMAGNETIC-ACTIVITY PLASMA-FLOW AMPTE-UKS CONVECTION MAGNETOSPHERE |
description |
Abstract. A discussion is given of plasma flows in the dawn and nightside high-latitude ionospheric regions during substorms occurring on a contracted auroral oval, as observed using the EISCAT CP-4-A experiment. Supporting data from the PACE radar, Greenland magnetometer chain, SAMNET magnetometers and geostationary satellites are compared to the EISCAT observations. On 4 October 1989 a weak substorm with initial expansion phase onset signatures at 0030 UT, resulted in the convection reversal boundary observed by EISCAT (at ~0415 MLT) contracting rapidly poleward, causing a band of elevated ionospheric ion temperatures and a localised plasma density depletion. This polar cap contraction event is shown to be associated with various substorm signatures; Pi2 pulsations at mid-latitudes, magnetic bays in the midnight sector and particle injections at geosynchronous orbit. A similar event was observed on the following day around 0230 UT (~0515 MLT) with the unusual and significant difference that two convection reversals were observed, both contracting poleward. We show that this feature is not an ionospheric signature of two active reconnection neutral lines as predicted by the near-Earth neutral model before the plasmoid is "pinched off", and present two alternative explanations in terms of (1) viscous and lobe circulation cells and (2) polar cap contraction during northward IMF. The voltage associated with the anti-sunward flow between the reversals reaches a maximum of 13 kV during the substorm expansion phase. This suggests it to be associated with the polar cap contraction and caused by the reconnection of open flux in the geomagnetic tail which has mimicked "viscous-like" momentum transfer across the magnetopause. 45149 |
format |
Article in Journal/Newspaper |
author |
Fox, N. J. Lockwood, M. Cowley, S. W. H. Freeman, M. P. Friischristensen, E. Milling, D. K. Pinnock, M. Reeves, G. D. |
author_facet |
Fox, N. J. Lockwood, M. Cowley, S. W. H. Freeman, M. P. Friischristensen, E. Milling, D. K. Pinnock, M. Reeves, G. D. |
author_sort |
Fox, N. J. |
title |
EISCAT observations of unusual flows in the morning sector associated with weak substorm activity |
title_short |
EISCAT observations of unusual flows in the morning sector associated with weak substorm activity |
title_full |
EISCAT observations of unusual flows in the morning sector associated with weak substorm activity |
title_fullStr |
EISCAT observations of unusual flows in the morning sector associated with weak substorm activity |
title_full_unstemmed |
EISCAT observations of unusual flows in the morning sector associated with weak substorm activity |
title_sort |
eiscat observations of unusual flows in the morning sector associated with weak substorm activity |
publisher |
SPRINGER VERLAG |
publishDate |
2012 |
url |
http://hdl.handle.net/2381/19558 http://www.ann-geophys.net/12/541/1994/angeo-12-541-1994.html https://doi.org/10.1007/s00585-994-0541-2 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
EISCAT Greenland |
genre_facet |
EISCAT Greenland |
op_source |
Web of Science http://webofknowledge.com |
op_relation |
ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES, 1994, 12 (6), pp. 541-553 0992-7689 http://hdl.handle.net/2381/19558 http://www.ann-geophys.net/12/541/1994/angeo-12-541-1994.html doi:10.1007/s00585-994-0541-2 |
op_rights |
Copyright © European Geosciences Union 1994 |
op_doi |
https://doi.org/10.1007/s00585-994-0541-2 |
container_title |
Annales Geophysicae |
container_volume |
12 |
container_issue |
6 |
container_start_page |
541 |
op_container_end_page |
553 |
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1766400060854108160 |