Excitation of Alfvén waves by modulated HF heating of the ionosphere, with application to FAST observations
International audience 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 direc...
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ftinsu:oai:HAL:hal-00316920v1 2023-11-12T04:16:36+01:00 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. Department of Physics and Astronomy Leicester University of Leicester 2002 https://hal.science/hal-00316920 https://hal.science/hal-00316920/document https://hal.science/hal-00316920/file/angeo-20-57-2002.pdf en eng HAL CCSD European Geosciences Union hal-00316920 https://hal.science/hal-00316920 https://hal.science/hal-00316920/document https://hal.science/hal-00316920/file/angeo-20-57-2002.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316920 Annales Geophysicae, 2002, 20 (1), pp.57-67 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/article Journal articles 2002 ftinsu 2023-10-25T16:25:27Z International audience 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 · 10 12 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 Institut national des sciences de l'Univers: HAL-INSU Norway Tromsø |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences 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 |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience 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 · 10 12 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. |
author2 |
Department of Physics and Astronomy Leicester University of Leicester |
format |
Article in Journal/Newspaper |
author |
Kolesnikova, E. Robinson, T. R. Davies, J. A. Wright, D. M. Lester, M. |
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 |
HAL CCSD |
publishDate |
2002 |
url |
https://hal.science/hal-00316920 https://hal.science/hal-00316920/document https://hal.science/hal-00316920/file/angeo-20-57-2002.pdf |
geographic |
Norway Tromsø |
geographic_facet |
Norway Tromsø |
genre |
EISCAT Tromsø |
genre_facet |
EISCAT Tromsø |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316920 Annales Geophysicae, 2002, 20 (1), pp.57-67 |
op_relation |
hal-00316920 https://hal.science/hal-00316920 https://hal.science/hal-00316920/document https://hal.science/hal-00316920/file/angeo-20-57-2002.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782333669511266304 |