A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora
A poleward-progressing 630 nm optical feature is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT) by a meridian-scanning photometer (MSP) located at Ny Ålesund, Svalbard. Simultaneous coherent HF radar measurements indicate a region of poleward-expanding backscatter with rap...
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1997
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ftdoajarticles:oai:doaj.org/article:6a64cd6c0d8341d89ab50afe5251e623 2023-05-15T17:48:28+02:00 A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora S. E. Milan M. Lester J. Moen 1997-11-01T00:00:00Z https://doi.org/10.1007/s00585-997-1388-0 https://doaj.org/article/6a64cd6c0d8341d89ab50afe5251e623 EN eng Copernicus Publications https://www.ann-geophys.net/15/1388/1997/angeo-15-1388-1997.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.1007/s00585-997-1388-0 0992-7689 1432-0576 https://doaj.org/article/6a64cd6c0d8341d89ab50afe5251e623 Annales Geophysicae, Vol 15, Pp 1388-1398 (1997) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 1997 ftdoajarticles https://doi.org/10.1007/s00585-997-1388-0 2022-12-31T01:14:47Z A poleward-progressing 630 nm optical feature is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT) by a meridian-scanning photometer (MSP) located at Ny Ålesund, Svalbard. Simultaneous coherent HF radar measurements indicate a region of poleward-expanding backscatter with rapid sunward plasma flow velocity along the MSP meridian. Spatial maps of the backscatter indicate a stationary backscatter feature aligned obliquely with respect to the MSP meridian, which produces an impression of poleward-expansion as the MSP progresses to later MLT. Two interpretations of the observations are possible, depending on whether the arc system is considered to move (time-dependent) or to be stationary in time and apparent motion is produced as the MSP meridian rotates underneath it (time-independent). The first interpretation is as a poleward motion of an east-west aligned auroral arc. In this case the appearance of the region of backscatter is not associated with the optical feature, though the velocities within it are enhanced when the two are co-located. The second interpretation is as a polar arc or theta aurora, common features of the polar cap under the prevailing IMF northwards conditions. In this case the backscatter appears as an approximately 150 km wide region adjacent to the optical arc. In both interpretations the luminosity of the optical feature appears related to the magnitude of the plasma flow velocity. The optical features presented here do not generate appreciable HF coherent backscatter, and are only identifiable in the backscatter data as a modification of the flow by the arc electrodynamics. Article in Journal/Newspaper Ny Ålesund Ny-Ålesund Svalbard Directory of Open Access Journals: DOAJ Articles Ny-Ålesund Svalbard Annales Geophysicae 15 11 1388 1398 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
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 S. E. Milan M. Lester J. Moen A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
A poleward-progressing 630 nm optical feature is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT) by a meridian-scanning photometer (MSP) located at Ny Ålesund, Svalbard. Simultaneous coherent HF radar measurements indicate a region of poleward-expanding backscatter with rapid sunward plasma flow velocity along the MSP meridian. Spatial maps of the backscatter indicate a stationary backscatter feature aligned obliquely with respect to the MSP meridian, which produces an impression of poleward-expansion as the MSP progresses to later MLT. Two interpretations of the observations are possible, depending on whether the arc system is considered to move (time-dependent) or to be stationary in time and apparent motion is produced as the MSP meridian rotates underneath it (time-independent). The first interpretation is as a poleward motion of an east-west aligned auroral arc. In this case the appearance of the region of backscatter is not associated with the optical feature, though the velocities within it are enhanced when the two are co-located. The second interpretation is as a polar arc or theta aurora, common features of the polar cap under the prevailing IMF northwards conditions. In this case the backscatter appears as an approximately 150 km wide region adjacent to the optical arc. In both interpretations the luminosity of the optical feature appears related to the magnitude of the plasma flow velocity. The optical features presented here do not generate appreciable HF coherent backscatter, and are only identifiable in the backscatter data as a modification of the flow by the arc electrodynamics. |
format |
Article in Journal/Newspaper |
author |
S. E. Milan M. Lester J. Moen |
author_facet |
S. E. Milan M. Lester J. Moen |
author_sort |
S. E. Milan |
title |
A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
title_short |
A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
title_full |
A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
title_fullStr |
A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
title_full_unstemmed |
A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
title_sort |
comparison of optical and coherent hf radar backscatter observations of a post-midnight aurora |
publisher |
Copernicus Publications |
publishDate |
1997 |
url |
https://doi.org/10.1007/s00585-997-1388-0 https://doaj.org/article/6a64cd6c0d8341d89ab50afe5251e623 |
geographic |
Ny-Ålesund Svalbard |
geographic_facet |
Ny-Ålesund Svalbard |
genre |
Ny Ålesund Ny-Ålesund Svalbard |
genre_facet |
Ny Ålesund Ny-Ålesund Svalbard |
op_source |
Annales Geophysicae, Vol 15, Pp 1388-1398 (1997) |
op_relation |
https://www.ann-geophys.net/15/1388/1997/angeo-15-1388-1997.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.1007/s00585-997-1388-0 0992-7689 1432-0576 https://doaj.org/article/6a64cd6c0d8341d89ab50afe5251e623 |
op_doi |
https://doi.org/10.1007/s00585-997-1388-0 |
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Annales Geophysicae |
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15 |
container_issue |
11 |
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1388 |
op_container_end_page |
1398 |
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