E-region echo characteristics governed by auroral arc electrodynamics
Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC) and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mech...
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doaj-4731a63ea313452fbaf767206f7073c32020-11-24T22:24:37ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762003-07-01211567157510.5194/angeo-21-1567-2003E-region echo characteristics governed by auroral arc electrodynamicsS. E. Milan0N. Sato1M. Lester2Y. Murata3Y. Shinkai4H. Doi5H. U. Frey6T. Saemundsson7Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UKNational Institute of Polar Research, Tokyo 173-8515, JapanDepartment of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UKGraduate University for Advanced Studies, Tokyo 173-8515, JapanGraduate University for Advanced Studies, Tokyo 173-8515, JapanTokai University, Kanagawa 259-1292, JapanSpace Sciences Laboratory, University of California at Berkeley, California, USAScience Institute, University of Iceland, Reykjavik IS-107, IcelandObservations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC) and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.<br><br><b>Key words. </b>Ionosphere (ionospheric irregularities; electric fields and currents)https://www.ann-geophys.net/21/1567/2003/angeo-21-1567-2003.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
S. E. Milan N. Sato M. Lester Y. Murata Y. Shinkai H. Doi H. U. Frey T. Saemundsson |
spellingShingle |
S. E. Milan N. Sato M. Lester Y. Murata Y. Shinkai H. Doi H. U. Frey T. Saemundsson E-region echo characteristics governed by auroral arc electrodynamics Annales Geophysicae |
author_facet |
S. E. Milan N. Sato M. Lester Y. Murata Y. Shinkai H. Doi H. U. Frey T. Saemundsson |
author_sort |
S. E. Milan |
title |
E-region echo characteristics governed by auroral arc electrodynamics |
title_short |
E-region echo characteristics governed by auroral arc electrodynamics |
title_full |
E-region echo characteristics governed by auroral arc electrodynamics |
title_fullStr |
E-region echo characteristics governed by auroral arc electrodynamics |
title_full_unstemmed |
E-region echo characteristics governed by auroral arc electrodynamics |
title_sort |
e-region echo characteristics governed by auroral arc electrodynamics |
publisher |
Copernicus Publications |
series |
Annales Geophysicae |
issn |
0992-7689 1432-0576 |
publishDate |
2003-07-01 |
description |
Observations of a pair of
auroral arc features by two imagers, one ground- and one space-based, allows
the associated field-aligned current (FAC) and electric field structure to be
inferred. Simultaneous observations of HF radar echoes provide an insight into
the irregularity-generating mechanisms. This is especially interesting for the
E-region echoes observed, which form the focus of our analysis, and from which
several conclusions can be drawn, summarized as follows. Latitudinal variations
in echo characteristics are governed by the FAC and electric field background.
Particularly sharp boundaries are found at the edges of auroral arcs. Within
regions of auroral luminosity, echoes have Doppler shifts below the
ion-acoustic speed and are proportional to the electric field, suggesting
scatter from gradient drift waves. Regions of downward FAC are associated with
mixed high and low Doppler shift echoes. The high Doppler shift component is
greatly in excess of the ion-acoustic speed, but seems to be commensurate with
the driving electric field. The low Doppler shift component appears to be much
depressed below expectations.<br><br><b>Key words. </b>Ionosphere (ionospheric
irregularities; electric fields and currents) |
url |
https://www.ann-geophys.net/21/1567/2003/angeo-21-1567-2003.pdf |
work_keys_str_mv |
AT semilan eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT nsato eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT mlester eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT ymurata eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT yshinkai eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT hdoi eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT hufrey eregionechocharacteristicsgovernedbyauroralarcelectrodynamics AT tsaemundsson eregionechocharacteristicsgovernedbyauroralarcelectrodynamics |
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