The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere
A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT) auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-...
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ftdoajarticles:oai:doaj.org/article:cbe754a70f614fa1a962faa676c76464 2023-05-15T16:04:50+02:00 The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere J. Moen M. Lockwood K. Oksavik H. C. Carlson W. F. Denig A. P. van Eyken I. W. McCrea 2004-06-01T00:00:00Z https://doi.org/10.5194/angeo-22-1973-2004 https://doaj.org/article/cbe754a70f614fa1a962faa676c76464 EN eng Copernicus Publications https://www.ann-geophys.net/22/1973/2004/angeo-22-1973-2004.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-22-1973-2004 0992-7689 1432-0576 https://doaj.org/article/cbe754a70f614fa1a962faa676c76464 Annales Geophysicae, Vol 22, Pp 1973-1987 (2004) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2004 ftdoajarticles https://doi.org/10.5194/angeo-22-1973-2004 2022-12-31T02:07:20Z A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT) auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-region electron and ion gases (T e and T i , respectively) have been compared with concurrent observations of particle precipitation and field-perpendicular convection by DMSP satellites, in order to reveal a physical explanation for the persistent band of high T i , and to test the potential role of T i and T e gradients as possible markers for the open-closed field line boundary. The north/south movement of the equatorward T i boundary was found to be consistent with the contraction/expansion of the polar cap due to an unbalanced dayside and nightside reconnection. Sporadic intensifications in T i , recurring on ~10-min time scales, indicate that frictional heating was modulated by time-varying reconnection, and the band of high T i was located on open flux. However, the equatorward T i boundary was not found to be a close proxy of the open-closed boundary. The closest definable proxy of the open-closed boundary is the magnetosheath electron edge observed by DMSP. Although T e appears to be sensitive to magnetosheath electron fluxes, it is not found to be a suitable parameter for routine tracking of the open-closed boundary, as it involves case dependent analysis of the thermal balance. Finally, we have documented a region of newly-opened sunward convecting flux. This region is situated between the convection reversal boundary and the magnetosheath electron edge defining the open-closed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfvénic) magnetosheath electrons and the response in the ionospheric convection, conveyed to the ionosphere by the interior Alfvén wave. It represents a candidate footprint of the low-latitude boundary mixing layer on sunward ... Article in Journal/Newspaper EISCAT Directory of Open Access Journals: DOAJ Articles Annales Geophysicae 22 6 1973 1987 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
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ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 J. Moen M. Lockwood K. Oksavik H. C. Carlson W. F. Denig A. P. van Eyken I. W. McCrea The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT) auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-region electron and ion gases (T e and T i , respectively) have been compared with concurrent observations of particle precipitation and field-perpendicular convection by DMSP satellites, in order to reveal a physical explanation for the persistent band of high T i , and to test the potential role of T i and T e gradients as possible markers for the open-closed field line boundary. The north/south movement of the equatorward T i boundary was found to be consistent with the contraction/expansion of the polar cap due to an unbalanced dayside and nightside reconnection. Sporadic intensifications in T i , recurring on ~10-min time scales, indicate that frictional heating was modulated by time-varying reconnection, and the band of high T i was located on open flux. However, the equatorward T i boundary was not found to be a close proxy of the open-closed boundary. The closest definable proxy of the open-closed boundary is the magnetosheath electron edge observed by DMSP. Although T e appears to be sensitive to magnetosheath electron fluxes, it is not found to be a suitable parameter for routine tracking of the open-closed boundary, as it involves case dependent analysis of the thermal balance. Finally, we have documented a region of newly-opened sunward convecting flux. This region is situated between the convection reversal boundary and the magnetosheath electron edge defining the open-closed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfvénic) magnetosheath electrons and the response in the ionospheric convection, conveyed to the ionosphere by the interior Alfvén wave. It represents a candidate footprint of the low-latitude boundary mixing layer on sunward ... |
format |
Article in Journal/Newspaper |
author |
J. Moen M. Lockwood K. Oksavik H. C. Carlson W. F. Denig A. P. van Eyken I. W. McCrea |
author_facet |
J. Moen M. Lockwood K. Oksavik H. C. Carlson W. F. Denig A. P. van Eyken I. W. McCrea |
author_sort |
J. Moen |
title |
The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
title_short |
The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
title_full |
The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
title_fullStr |
The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
title_full_unstemmed |
The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
title_sort |
dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
publisher |
Copernicus Publications |
publishDate |
2004 |
url |
https://doi.org/10.5194/angeo-22-1973-2004 https://doaj.org/article/cbe754a70f614fa1a962faa676c76464 |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
Annales Geophysicae, Vol 22, Pp 1973-1987 (2004) |
op_relation |
https://www.ann-geophys.net/22/1973/2004/angeo-22-1973-2004.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-22-1973-2004 0992-7689 1432-0576 https://doaj.org/article/cbe754a70f614fa1a962faa676c76464 |
op_doi |
https://doi.org/10.5194/angeo-22-1973-2004 |
container_title |
Annales Geophysicae |
container_volume |
22 |
container_issue |
6 |
container_start_page |
1973 |
op_container_end_page |
1987 |
_version_ |
1766400475025899520 |