Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements
Dayside merging between the interplanetary and terrestrial magnetic fields couples the solar wind electric field to the Earth's magnetosphere, increases the magnetospheric convection and results in efficient transport of solar wind energy into the magnetosphere. Subsequent reconnection of the l...
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ftdoajarticles:oai:doaj.org/article:a33846236b0a4727b87fe273f04c4b7f 2023-05-15T16:04:32+02:00 Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements N. Østgaard J. Moen S. B. Mende H. U. Frey T. J. Immel P. Gallop K. Oksavik M. Fujimoto 2005-01-01T00:00:00Z https://doi.org/10.5194/angeo-23-123-2005 https://doaj.org/article/a33846236b0a4727b87fe273f04c4b7f EN eng Copernicus Publications https://www.ann-geophys.net/23/123/2005/angeo-23-123-2005.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-23-123-2005 0992-7689 1432-0576 https://doaj.org/article/a33846236b0a4727b87fe273f04c4b7f Annales Geophysicae, Vol 23, Pp 123-134 (2005) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2005 ftdoajarticles https://doi.org/10.5194/angeo-23-123-2005 2022-12-31T13:52:22Z Dayside merging between the interplanetary and terrestrial magnetic fields couples the solar wind electric field to the Earth's magnetosphere, increases the magnetospheric convection and results in efficient transport of solar wind energy into the magnetosphere. Subsequent reconnection of the lobe magnetic field in the magnetotail transports energy into the closed magnetic field region. Combining global imaging and ground-based radar measurements, we estimate the reconnection rate in the magnetotail during two days of an EISCAT campaign in November-December 2000. Global images from the IMAGE FUV system guide us to identify ionospheric signatures of the open-closed field line boundary observed by the two EISCAT radars in Tromsø (VHF) and on Svalbard (ESR). Continuous radar and optical monitoring of the open-closed field line boundary is used to determine the location, orientation and velocity of the open-closed boundary and the ion flow velocity perpendicular to this boundary. The magnetotail reconnection electric field is found to be a bursty process that oscillates between 0mV/m and 1mV/m with ~10-15min periods. These ULF oscillations are mainly due to the motion of the open-closed boundary. In situ measurements earthward of the reconnection site in the magnetotail by Geotail show similar oscillations in the duskward electric field. We also find that bursts of increased magnetotail reconnection do not necessarily have any associated auroral signatures. Finally, we find that the reconnection rate correlates poorly with the solar wind electric field. This indicates that the magnetotail reconnection is not directly driven, but is an internal magnetospheric process. Estimates of a coupling efficiency between the solar wind electric field and magnetotail reconnection only seem to be relevant as averages over long time intervals. The oscillation mode at 1mHz corresponds to the internal cavity mode with additional lower frequencies, 0.5 and 0.8mHz, that might be modulated by solar wind pressure variations. Article in Journal/Newspaper EISCAT Svalbard Tromsø Directory of Open Access Journals: DOAJ Articles Svalbard Tromsø Annales Geophysicae 23 1 123 134 |
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English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 N. Østgaard J. Moen S. B. Mende H. U. Frey T. J. Immel P. Gallop K. Oksavik M. Fujimoto Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
Dayside merging between the interplanetary and terrestrial magnetic fields couples the solar wind electric field to the Earth's magnetosphere, increases the magnetospheric convection and results in efficient transport of solar wind energy into the magnetosphere. Subsequent reconnection of the lobe magnetic field in the magnetotail transports energy into the closed magnetic field region. Combining global imaging and ground-based radar measurements, we estimate the reconnection rate in the magnetotail during two days of an EISCAT campaign in November-December 2000. Global images from the IMAGE FUV system guide us to identify ionospheric signatures of the open-closed field line boundary observed by the two EISCAT radars in Tromsø (VHF) and on Svalbard (ESR). Continuous radar and optical monitoring of the open-closed field line boundary is used to determine the location, orientation and velocity of the open-closed boundary and the ion flow velocity perpendicular to this boundary. The magnetotail reconnection electric field is found to be a bursty process that oscillates between 0mV/m and 1mV/m with ~10-15min periods. These ULF oscillations are mainly due to the motion of the open-closed boundary. In situ measurements earthward of the reconnection site in the magnetotail by Geotail show similar oscillations in the duskward electric field. We also find that bursts of increased magnetotail reconnection do not necessarily have any associated auroral signatures. Finally, we find that the reconnection rate correlates poorly with the solar wind electric field. This indicates that the magnetotail reconnection is not directly driven, but is an internal magnetospheric process. Estimates of a coupling efficiency between the solar wind electric field and magnetotail reconnection only seem to be relevant as averages over long time intervals. The oscillation mode at 1mHz corresponds to the internal cavity mode with additional lower frequencies, 0.5 and 0.8mHz, that might be modulated by solar wind pressure variations. |
format |
Article in Journal/Newspaper |
author |
N. Østgaard J. Moen S. B. Mende H. U. Frey T. J. Immel P. Gallop K. Oksavik M. Fujimoto |
author_facet |
N. Østgaard J. Moen S. B. Mende H. U. Frey T. J. Immel P. Gallop K. Oksavik M. Fujimoto |
author_sort |
N. Østgaard |
title |
Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements |
title_short |
Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements |
title_full |
Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements |
title_fullStr |
Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements |
title_full_unstemmed |
Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements |
title_sort |
estimates of magnetotail reconnection rate based on image fuv and eiscat measurements |
publisher |
Copernicus Publications |
publishDate |
2005 |
url |
https://doi.org/10.5194/angeo-23-123-2005 https://doaj.org/article/a33846236b0a4727b87fe273f04c4b7f |
geographic |
Svalbard Tromsø |
geographic_facet |
Svalbard Tromsø |
genre |
EISCAT Svalbard Tromsø |
genre_facet |
EISCAT Svalbard Tromsø |
op_source |
Annales Geophysicae, Vol 23, Pp 123-134 (2005) |
op_relation |
https://www.ann-geophys.net/23/123/2005/angeo-23-123-2005.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-23-123-2005 0992-7689 1432-0576 https://doaj.org/article/a33846236b0a4727b87fe273f04c4b7f |
op_doi |
https://doi.org/10.5194/angeo-23-123-2005 |
container_title |
Annales Geophysicae |
container_volume |
23 |
container_issue |
1 |
container_start_page |
123 |
op_container_end_page |
134 |
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1766400128618332160 |