Plasmaspheric storm time erosion

Unusually low whistler mode group delay times are observed by VLF Doppler receivers at both Faraday, Antarctica, and Dunedin, New Zealand, following magnetic storms. These are typically caused by plasmaspheric electron concentration depletions near L=2.4 and not by changes in the VLF wave propagatio...

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Published in:Journal of Geophysical Research: Space Physics
Main Authors: Clilverd, Mark A., Jenkins, Barbara, Thomson, Neil R.
Format: Article in Journal/Newspaper
Language:unknown
Published: American Geophysical Union 2000
Subjects:
Online Access:http://nora.nerc.ac.uk/id/eprint/20453/
https://doi.org/10.1029/1999JA900497
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spelling ftnerc:oai:nora.nerc.ac.uk:20453 2023-05-15T13:45:12+02:00 Plasmaspheric storm time erosion Clilverd, Mark A. Jenkins, Barbara Thomson, Neil R. 2000 http://nora.nerc.ac.uk/id/eprint/20453/ https://doi.org/10.1029/1999JA900497 unknown American Geophysical Union Clilverd, Mark A. orcid:0000-0002-7388-1529 Jenkins, Barbara; Thomson, Neil R. 2000 Plasmaspheric storm time erosion. Journal of Geophysical Research, 105 (A6). 12997-13008. https://doi.org/10.1029/1999JA900497 <https://doi.org/10.1029/1999JA900497> Publication - Article PeerReviewed 2000 ftnerc https://doi.org/10.1029/1999JA900497 2023-02-04T19:32:55Z Unusually low whistler mode group delay times are observed by VLF Doppler receivers at both Faraday, Antarctica, and Dunedin, New Zealand, following magnetic storms. These are typically caused by plasmaspheric electron concentration depletions near L=2.4 and not by changes in the VLF wave propagation path. Using a data set that is almost continuous since 1986, we find that depletions during storms in the solar minimum of 1995 are significantly deeper than in the minimum of 1986. Event studies at Faraday show that the electron concentration depletions caused by storms were about a factor of 2 in 1986 and a factor of 3–4 in 1995, independent of the time of year. However, the depletions observed by both sites are significantly deeper than those observed in 1958 and 1961 using natural whistlers (i.e., factors of 2–4 compared to 1.3). The Sheffield University Plasmasphere Ionosphere Model (SUPIM) has been used to investigate possible causes of the plasmaspheric electron concentration depletions observed in the whistler mode data. Thermospheric parameters, including a reduction in the concentration of neutral hydrogen and oxygen at all altitudes, were perturbed by a factor of 10 from their normal levels. However, the plasmaspheric depletions produced were only of the order of 10% after 27 hours. It is unlikely therefore that thermospheric modifications alone are responsible for the depletions observed in the data. Additionally, a tube of plasma was moved to higher L shell under the influence of an equatorial meridional E × B drift velocity of 1000 m s−1 and showed levels of depletion of about a factor of 2. Although it is possible to generate plasmaspheric concentration depletions using the drifting tube model, the depletions are smaller than those observed and the outward E × B drift velocity needed is a factor of 2 greater than those reported previously at L=2.4. It is therefore unlikely that the tube drifting mechanism is the principal cause of the observed plasmaspheric electron concentration depletions at L=2.4. ... Article in Journal/Newspaper Antarc* Antarctica Natural Environment Research Council: NERC Open Research Archive New Zealand Sheffield Faraday ENVELOPE(-64.256,-64.256,-65.246,-65.246) Journal of Geophysical Research: Space Physics 105 A6 12997 13008
institution Open Polar
collection Natural Environment Research Council: NERC Open Research Archive
op_collection_id ftnerc
language unknown
description Unusually low whistler mode group delay times are observed by VLF Doppler receivers at both Faraday, Antarctica, and Dunedin, New Zealand, following magnetic storms. These are typically caused by plasmaspheric electron concentration depletions near L=2.4 and not by changes in the VLF wave propagation path. Using a data set that is almost continuous since 1986, we find that depletions during storms in the solar minimum of 1995 are significantly deeper than in the minimum of 1986. Event studies at Faraday show that the electron concentration depletions caused by storms were about a factor of 2 in 1986 and a factor of 3–4 in 1995, independent of the time of year. However, the depletions observed by both sites are significantly deeper than those observed in 1958 and 1961 using natural whistlers (i.e., factors of 2–4 compared to 1.3). The Sheffield University Plasmasphere Ionosphere Model (SUPIM) has been used to investigate possible causes of the plasmaspheric electron concentration depletions observed in the whistler mode data. Thermospheric parameters, including a reduction in the concentration of neutral hydrogen and oxygen at all altitudes, were perturbed by a factor of 10 from their normal levels. However, the plasmaspheric depletions produced were only of the order of 10% after 27 hours. It is unlikely therefore that thermospheric modifications alone are responsible for the depletions observed in the data. Additionally, a tube of plasma was moved to higher L shell under the influence of an equatorial meridional E × B drift velocity of 1000 m s−1 and showed levels of depletion of about a factor of 2. Although it is possible to generate plasmaspheric concentration depletions using the drifting tube model, the depletions are smaller than those observed and the outward E × B drift velocity needed is a factor of 2 greater than those reported previously at L=2.4. It is therefore unlikely that the tube drifting mechanism is the principal cause of the observed plasmaspheric electron concentration depletions at L=2.4. ...
format Article in Journal/Newspaper
author Clilverd, Mark A.
Jenkins, Barbara
Thomson, Neil R.
spellingShingle Clilverd, Mark A.
Jenkins, Barbara
Thomson, Neil R.
Plasmaspheric storm time erosion
author_facet Clilverd, Mark A.
Jenkins, Barbara
Thomson, Neil R.
author_sort Clilverd, Mark A.
title Plasmaspheric storm time erosion
title_short Plasmaspheric storm time erosion
title_full Plasmaspheric storm time erosion
title_fullStr Plasmaspheric storm time erosion
title_full_unstemmed Plasmaspheric storm time erosion
title_sort plasmaspheric storm time erosion
publisher American Geophysical Union
publishDate 2000
url http://nora.nerc.ac.uk/id/eprint/20453/
https://doi.org/10.1029/1999JA900497
long_lat ENVELOPE(-64.256,-64.256,-65.246,-65.246)
geographic New Zealand
Sheffield
Faraday
geographic_facet New Zealand
Sheffield
Faraday
genre Antarc*
Antarctica
genre_facet Antarc*
Antarctica
op_relation Clilverd, Mark A. orcid:0000-0002-7388-1529
Jenkins, Barbara; Thomson, Neil R. 2000 Plasmaspheric storm time erosion. Journal of Geophysical Research, 105 (A6). 12997-13008. https://doi.org/10.1029/1999JA900497 <https://doi.org/10.1029/1999JA900497>
op_doi https://doi.org/10.1029/1999JA900497
container_title Journal of Geophysical Research: Space Physics
container_volume 105
container_issue A6
container_start_page 12997
op_container_end_page 13008
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