EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary
The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6 degree cgmLat) and Longyearbyen (75.2 degree cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent sc...
Published in: | Annales Geophysicae |
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Language: | English |
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Department of Physical Sciences, University of Oulu, Finland
2008
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Online Access: | http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102619 https://doi.org/10.5194/angeo-26-87-2008 |
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ftumeauniv:oai:DiVA.org:umu-102619 2023-10-09T21:51:08+02:00 EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary Aikio, Anita T. Pitkänen, Timo Fontaine, Dominic Dandouras, Iannis Amm, Olaf Kozlovsky, Alexander Vaivads, Andris Fazakerley, Andrew 2008 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102619 https://doi.org/10.5194/angeo-26-87-2008 eng eng Department of Physical Sciences, University of Oulu, Finland CETP/UVSQ, Velizy, France CESR/CNRS, Toulouse, France Finnish meteorological Institute, Helsinki, Finland Department of Physical Sciences, University of Oulu, Finland; Sodankylä Geophysical Observatory, Sodankylä, Finland Swedish Institute of Space Physics, Ångströmlaboratoriet, Uppsala, Sweden Mullard Space Science Laboratory, University College, London, UK Copernicus Publications Annales Geophysicae, 0992-7689, 2008, 26, s. 87-105 orcid:0000-0002-5681-0366 http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102619 doi:10.5194/angeo-26-87-2008 info:eu-repo/semantics/openAccess Ionosphere (Auroral ionosphere Electric fields and currents Storms and substorms) Fusion Plasma and Space Physics plasma och rymdfysik Article in journal info:eu-repo/semantics/article text 2008 ftumeauniv https://doi.org/10.5194/angeo-26-87-2008 2023-09-22T13:51:37Z The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6 degree cgmLat) and Longyearbyen (75.2 degree cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5 degree cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4RE mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H+ and O+ ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2 degree during ˜ 5 min. The beginning of the poleward motion of the PCB was associated with an intensification of ... Article in Journal/Newspaper EISCAT Longyearbyen Tromsø Umeå University: Publications (DiVA) Cowley ENVELOPE(-134.909,-134.909,60.518,60.518) Lockwood ENVELOPE(167.400,167.400,-84.150,-84.150) Longyearbyen Tromsø Annales Geophysicae 26 1 87 105 |
institution |
Open Polar |
collection |
Umeå University: Publications (DiVA) |
op_collection_id |
ftumeauniv |
language |
English |
topic |
Ionosphere (Auroral ionosphere Electric fields and currents Storms and substorms) Fusion Plasma and Space Physics plasma och rymdfysik |
spellingShingle |
Ionosphere (Auroral ionosphere Electric fields and currents Storms and substorms) Fusion Plasma and Space Physics plasma och rymdfysik Aikio, Anita T. Pitkänen, Timo Fontaine, Dominic Dandouras, Iannis Amm, Olaf Kozlovsky, Alexander Vaivads, Andris Fazakerley, Andrew EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary |
topic_facet |
Ionosphere (Auroral ionosphere Electric fields and currents Storms and substorms) Fusion Plasma and Space Physics plasma och rymdfysik |
description |
The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6 degree cgmLat) and Longyearbyen (75.2 degree cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5 degree cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4RE mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H+ and O+ ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2 degree during ˜ 5 min. The beginning of the poleward motion of the PCB was associated with an intensification of ... |
format |
Article in Journal/Newspaper |
author |
Aikio, Anita T. Pitkänen, Timo Fontaine, Dominic Dandouras, Iannis Amm, Olaf Kozlovsky, Alexander Vaivads, Andris Fazakerley, Andrew |
author_facet |
Aikio, Anita T. Pitkänen, Timo Fontaine, Dominic Dandouras, Iannis Amm, Olaf Kozlovsky, Alexander Vaivads, Andris Fazakerley, Andrew |
author_sort |
Aikio, Anita T. |
title |
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary |
title_short |
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary |
title_full |
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary |
title_fullStr |
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary |
title_full_unstemmed |
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary |
title_sort |
eiscat and cluster observations in the vicinity of the dynamical polar cap boundary |
publisher |
Department of Physical Sciences, University of Oulu, Finland |
publishDate |
2008 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102619 https://doi.org/10.5194/angeo-26-87-2008 |
long_lat |
ENVELOPE(-134.909,-134.909,60.518,60.518) ENVELOPE(167.400,167.400,-84.150,-84.150) |
geographic |
Cowley Lockwood Longyearbyen Tromsø |
geographic_facet |
Cowley Lockwood Longyearbyen Tromsø |
genre |
EISCAT Longyearbyen Tromsø |
genre_facet |
EISCAT Longyearbyen Tromsø |
op_relation |
Annales Geophysicae, 0992-7689, 2008, 26, s. 87-105 orcid:0000-0002-5681-0366 http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102619 doi:10.5194/angeo-26-87-2008 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/angeo-26-87-2008 |
container_title |
Annales Geophysicae |
container_volume |
26 |
container_issue |
1 |
container_start_page |
87 |
op_container_end_page |
105 |
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1779314220999901184 |