Nightside studies of coherent HF Radar spectral width behaviour
A previous case study found a relationship between high spectral width measured by the CUTLASS Finland HF radar and elevated electron temperatures observed by the EISCAT and ESR incoherent scatter radars in the post-midnight sector of magnetic local time. This paper expands that work by briefly re-e...
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ftdoajarticles:oai:doaj.org/article:37f59ce82a92409ba0e8686803c4d22d 2023-05-15T16:04:50+02:00 Nightside studies of coherent HF Radar spectral width behaviour E. E. Woodfield J. A. Davies M. Lester T. K. Yeoman P. Eglitis M. Lockwood 2002-09-01T00:00:00Z https://doi.org/10.5194/angeo-20-1399-2002 https://doaj.org/article/37f59ce82a92409ba0e8686803c4d22d EN eng Copernicus Publications https://www.ann-geophys.net/20/1399/2002/angeo-20-1399-2002.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-20-1399-2002 0992-7689 1432-0576 https://doaj.org/article/37f59ce82a92409ba0e8686803c4d22d Annales Geophysicae, Vol 20, Pp 1399-1413 (2002) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2002 ftdoajarticles https://doi.org/10.5194/angeo-20-1399-2002 2022-12-31T13:15:18Z A previous case study found a relationship between high spectral width measured by the CUTLASS Finland HF radar and elevated electron temperatures observed by the EISCAT and ESR incoherent scatter radars in the post-midnight sector of magnetic local time. This paper expands that work by briefly re-examining that interval and looking in depth at two further case studies. In all three cases a region of high HF spectral width (>200 ms -1 ) exists poleward of a region of low HF spectral width (<200 ms -1 ). Each case, however, occurs under quite different geomagnetic conditions. The original case study occurred during an interval with no observed electrojet activity, the second study during a transition from quiet to active conditions with a clear band of ion frictional heating indicating the location of the flow reversal boundary, and the third during an isolated sub-storm. These case studies indicate that the relationship between elevated electron temperature and high HF radar spectral width appears on closed field lines after 03:00 magnetic local time (MLT) on the nightside. It is not clear whether the same relationship would hold on open field lines, since our analysis of this relationship is restricted in latitude. We find two important properties of high spectral width data on the nightside. Firstly the high spectral width values occur on both open and closed field lines, and secondly that the power spectra which exhibit high widths are both single-peak and multiple-peak. In general the regions of high spectral width (>200 ms -1 ) have more multiple-peak spectra than the regions of low spectral widths whilst still maintaining a majority of single-peak spectra. We also find that the region of ion frictional heating is collocated with many multiple-peak HF spectra. Several mechanisms for the generation of high spectral width have been proposed which would produce multiple-peak spectra, these are discussed in relation to the data presented here. Since the regions of high spectral width are observed both ... Article in Journal/Newspaper EISCAT Directory of Open Access Journals: DOAJ Articles Annales Geophysicae 20 9 1399 1413 |
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Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
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Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 E. E. Woodfield J. A. Davies M. Lester T. K. Yeoman P. Eglitis M. Lockwood Nightside studies of coherent HF Radar spectral width behaviour |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
A previous case study found a relationship between high spectral width measured by the CUTLASS Finland HF radar and elevated electron temperatures observed by the EISCAT and ESR incoherent scatter radars in the post-midnight sector of magnetic local time. This paper expands that work by briefly re-examining that interval and looking in depth at two further case studies. In all three cases a region of high HF spectral width (>200 ms -1 ) exists poleward of a region of low HF spectral width (<200 ms -1 ). Each case, however, occurs under quite different geomagnetic conditions. The original case study occurred during an interval with no observed electrojet activity, the second study during a transition from quiet to active conditions with a clear band of ion frictional heating indicating the location of the flow reversal boundary, and the third during an isolated sub-storm. These case studies indicate that the relationship between elevated electron temperature and high HF radar spectral width appears on closed field lines after 03:00 magnetic local time (MLT) on the nightside. It is not clear whether the same relationship would hold on open field lines, since our analysis of this relationship is restricted in latitude. We find two important properties of high spectral width data on the nightside. Firstly the high spectral width values occur on both open and closed field lines, and secondly that the power spectra which exhibit high widths are both single-peak and multiple-peak. In general the regions of high spectral width (>200 ms -1 ) have more multiple-peak spectra than the regions of low spectral widths whilst still maintaining a majority of single-peak spectra. We also find that the region of ion frictional heating is collocated with many multiple-peak HF spectra. Several mechanisms for the generation of high spectral width have been proposed which would produce multiple-peak spectra, these are discussed in relation to the data presented here. Since the regions of high spectral width are observed both ... |
format |
Article in Journal/Newspaper |
author |
E. E. Woodfield J. A. Davies M. Lester T. K. Yeoman P. Eglitis M. Lockwood |
author_facet |
E. E. Woodfield J. A. Davies M. Lester T. K. Yeoman P. Eglitis M. Lockwood |
author_sort |
E. E. Woodfield |
title |
Nightside studies of coherent HF Radar spectral width behaviour |
title_short |
Nightside studies of coherent HF Radar spectral width behaviour |
title_full |
Nightside studies of coherent HF Radar spectral width behaviour |
title_fullStr |
Nightside studies of coherent HF Radar spectral width behaviour |
title_full_unstemmed |
Nightside studies of coherent HF Radar spectral width behaviour |
title_sort |
nightside studies of coherent hf radar spectral width behaviour |
publisher |
Copernicus Publications |
publishDate |
2002 |
url |
https://doi.org/10.5194/angeo-20-1399-2002 https://doaj.org/article/37f59ce82a92409ba0e8686803c4d22d |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
Annales Geophysicae, Vol 20, Pp 1399-1413 (2002) |
op_relation |
https://www.ann-geophys.net/20/1399/2002/angeo-20-1399-2002.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-20-1399-2002 0992-7689 1432-0576 https://doaj.org/article/37f59ce82a92409ba0e8686803c4d22d |
op_doi |
https://doi.org/10.5194/angeo-20-1399-2002 |
container_title |
Annales Geophysicae |
container_volume |
20 |
container_issue |
9 |
container_start_page |
1399 |
op_container_end_page |
1413 |
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1766400465398923264 |