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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Main Authors: Woodfield, E.E., Davies, J.A., Lester, M., Yeoman, T.K., Eglitis, P., Lockwood, M.
Format: Article in Journal/Newspaper
Language:unknown
Published: 2002
Subjects:
Online Access:https://eprints.soton.ac.uk/9152/
http://www.copernicus.org/EGU/annales/20/9/1399.htm
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spelling ftsouthampton:oai:eprints.soton.ac.uk:9152 2024-06-09T07:45:41+00:00 Nightside studies of coherent HF Radar spectral width behaviour Woodfield, E.E. Davies, J.A. Lester, M. Yeoman, T.K. Eglitis, P. Lockwood, M. 2002 https://eprints.soton.ac.uk/9152/ http://www.copernicus.org/EGU/annales/20/9/1399.htm unknown Woodfield, E.E., Davies, J.A., Lester, M., Yeoman, T.K., Eglitis, P. and Lockwood, M. (2002) Nightside studies of coherent HF Radar spectral width behaviour. Annales Geophysicae, 20, 1399-1413. Article PeerReviewed 2002 ftsouthampton 2024-05-10T06:09:49Z 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 on ... Article in Journal/Newspaper EISCAT University of Southampton: e-Prints Soton
institution Open Polar
collection University of Southampton: e-Prints Soton
op_collection_id ftsouthampton
language unknown
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 on ...
format Article in Journal/Newspaper
author Woodfield, E.E.
Davies, J.A.
Lester, M.
Yeoman, T.K.
Eglitis, P.
Lockwood, M.
spellingShingle Woodfield, E.E.
Davies, J.A.
Lester, M.
Yeoman, T.K.
Eglitis, P.
Lockwood, M.
Nightside studies of coherent HF Radar spectral width behaviour
author_facet Woodfield, E.E.
Davies, J.A.
Lester, M.
Yeoman, T.K.
Eglitis, P.
Lockwood, M.
author_sort Woodfield, E.E.
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
publishDate 2002
url https://eprints.soton.ac.uk/9152/
http://www.copernicus.org/EGU/annales/20/9/1399.htm
genre EISCAT
genre_facet EISCAT
op_relation Woodfield, E.E., Davies, J.A., Lester, M., Yeoman, T.K., Eglitis, P. and Lockwood, M. (2002) Nightside studies of coherent HF Radar spectral width behaviour. Annales Geophysicae, 20, 1399-1413.
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