Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations
During the operation of the EISCAT high power facility (heater) at Tromsø, Norway, on 8 October 1998, the FAST spacecraft made electric field and particle observations in the inner magnetosphere at 0.39 Earth radii above the heated ionospheric region. Measurements of the direct current electric fiel...
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European Geosciences Union (EGU), Copernicus Publications, Springer Verlag (Germany)
2009
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Online Access: | http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html http://hdl.handle.net/2381/710 https://doi.org/10.5194/angeo-20-57-2002 |
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ftleicester:oai:lra.le.ac.uk:2381/710 2023-05-15T16:04:37+02:00 Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations Kolesnikova, E. Robinson, T. R. Davies, J. A. Wright, D. M. Lester, M. 2009-12-08T16:24:13Z http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html http://hdl.handle.net/2381/710 https://doi.org/10.5194/angeo-20-57-2002 en eng European Geosciences Union (EGU), Copernicus Publications, Springer Verlag (Germany) RAE 2007 Radio and Space Plasma Physics Annales Geophysicae: Atmospheres Hydrospheres and Space Science, 2002, 20 (1), pp.57-67 0992-7689 http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html http://hdl.handle.net/2381/710 doi:10.5194/angeo-20-57-2002 Available from the publisher website at http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html © Author(s) 2002. This work is distributed under the Creative Commons Attribution 3.0 License. CC-BY Article 2009 ftleicester https://doi.org/10.5194/angeo-20-57-2002 2019-03-22T20:13:54Z During the operation of the EISCAT high power facility (heater) at Tromsø, Norway, on 8 October 1998, the FAST spacecraft made electric field and particle observations in the inner magnetosphere at 0.39 Earth radii above the heated ionospheric region. Measurements of the direct current electric field clearly exhibit oscillations with a frequency close to the modulated frequency of heater ( ~ 3 Hz) and an amplitude of ~ 2 - 5 mV m-1. Thermal electron data from the electrostatic analyser show the modulation at the same frequency of the downward electron fluxes. During this period the EISCAT UHF incoherent scatter radar, sited also at Tromsø, measured a significant enhancement of the electron density in E-layer up to 2 · 1012 m-3. These observations have prompted us to make quantitative estimates of the expected pulsations in the inner magnetosphere caused by the modulated HF heating of lower ionosphere. Under the conditions of the strong electron precipitation in the ionosphere, which took place during the FAST observations, the primary current caused by the perturbation of the conductivity in the heated region is closed entirely by the parallel current which leaks into the magnetosphere. In such circumstances the conditions at the ionosphere-magnetosphere boundary are most favourable for the launching of an Alfvén wave: it is launched from the node in the gradient of the scalar potential which is proportional to the parallel current. The parallel electric field of the Alfvén wave is significant in the region where the electron inertial length is of order of the transverse wavelength of the Alfvén wave or larger and may effectively accelerate superthermal electrons downward into the ionosphere. Article in Journal/Newspaper EISCAT Tromsø University of Leicester: Leicester Research Archive (LRA) Norway Tromsø Annales Geophysicae 20 1 57 67 |
institution |
Open Polar |
collection |
University of Leicester: Leicester Research Archive (LRA) |
op_collection_id |
ftleicester |
language |
English |
description |
During the operation of the EISCAT high power facility (heater) at Tromsø, Norway, on 8 October 1998, the FAST spacecraft made electric field and particle observations in the inner magnetosphere at 0.39 Earth radii above the heated ionospheric region. Measurements of the direct current electric field clearly exhibit oscillations with a frequency close to the modulated frequency of heater ( ~ 3 Hz) and an amplitude of ~ 2 - 5 mV m-1. Thermal electron data from the electrostatic analyser show the modulation at the same frequency of the downward electron fluxes. During this period the EISCAT UHF incoherent scatter radar, sited also at Tromsø, measured a significant enhancement of the electron density in E-layer up to 2 · 1012 m-3. These observations have prompted us to make quantitative estimates of the expected pulsations in the inner magnetosphere caused by the modulated HF heating of lower ionosphere. Under the conditions of the strong electron precipitation in the ionosphere, which took place during the FAST observations, the primary current caused by the perturbation of the conductivity in the heated region is closed entirely by the parallel current which leaks into the magnetosphere. In such circumstances the conditions at the ionosphere-magnetosphere boundary are most favourable for the launching of an Alfvén wave: it is launched from the node in the gradient of the scalar potential which is proportional to the parallel current. The parallel electric field of the Alfvén wave is significant in the region where the electron inertial length is of order of the transverse wavelength of the Alfvén wave or larger and may effectively accelerate superthermal electrons downward into the ionosphere. |
format |
Article in Journal/Newspaper |
author |
Kolesnikova, E. Robinson, T. R. Davies, J. A. Wright, D. M. Lester, M. |
spellingShingle |
Kolesnikova, E. Robinson, T. R. Davies, J. A. Wright, D. M. Lester, M. Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations |
author_facet |
Kolesnikova, E. Robinson, T. R. Davies, J. A. Wright, D. M. Lester, M. |
author_sort |
Kolesnikova, E. |
title |
Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations |
title_short |
Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations |
title_full |
Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations |
title_fullStr |
Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations |
title_full_unstemmed |
Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations |
title_sort |
excitation of alfvén waves by modulated hf heating of the ionosphere, with application to fast observations |
publisher |
European Geosciences Union (EGU), Copernicus Publications, Springer Verlag (Germany) |
publishDate |
2009 |
url |
http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html http://hdl.handle.net/2381/710 https://doi.org/10.5194/angeo-20-57-2002 |
geographic |
Norway Tromsø |
geographic_facet |
Norway Tromsø |
genre |
EISCAT Tromsø |
genre_facet |
EISCAT Tromsø |
op_relation |
RAE 2007 Radio and Space Plasma Physics Annales Geophysicae: Atmospheres Hydrospheres and Space Science, 2002, 20 (1), pp.57-67 0992-7689 http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html http://hdl.handle.net/2381/710 doi:10.5194/angeo-20-57-2002 |
op_rights |
Available from the publisher website at http://www.ann-geophys.net/20/57/2002/angeo-20-57-2002.html © Author(s) 2002. This work is distributed under the Creative Commons Attribution 3.0 License. |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/angeo-20-57-2002 |
container_title |
Annales Geophysicae |
container_volume |
20 |
container_issue |
1 |
container_start_page |
57 |
op_container_end_page |
67 |
_version_ |
1766400229091835904 |