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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ftleicesterunfig:oai:figshare.com:article/10115297 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://figshare.com/articles/journal_contribution/A_comparison_of_optical_and_coherent_HF_radar_backscatter_observations_of_a_post-midnight_aurora/10115297 unknown 2381/19757 https://figshare.com/articles/journal_contribution/A_comparison_of_optical_and_coherent_HF_radar_backscatter_observations_of_a_post-midnight_aurora/10115297 All Rights Reserved Uncategorized Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD SMALL-SCALE IRREGULARITIES LATITUDE F-REGION SUN-ALIGNED ARCS POLAR-CAP ELECTRIC-FIELD NORTHWARD CONVECTION PATTERNS TIMES Text Journal contribution 1997 ftleicesterunfig 2021-11-11T20:04:58Z 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. Other Non-Article Part of Journal/Newspaper Ny Ålesund Ny-Ålesund Svalbard University of Leicester: Figshare Svalbard Ny-Ålesund |
institution |
Open Polar |
collection |
University of Leicester: Figshare |
op_collection_id |
ftleicesterunfig |
language |
unknown |
topic |
Uncategorized Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD SMALL-SCALE IRREGULARITIES LATITUDE F-REGION SUN-ALIGNED ARCS POLAR-CAP ELECTRIC-FIELD NORTHWARD CONVECTION PATTERNS TIMES |
spellingShingle |
Uncategorized Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD SMALL-SCALE IRREGULARITIES LATITUDE F-REGION SUN-ALIGNED ARCS POLAR-CAP ELECTRIC-FIELD NORTHWARD CONVECTION PATTERNS TIMES S. E. Milan M. Lester J. Moen A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
topic_facet |
Uncategorized Science & Technology Physical Sciences Astronomy & Astrophysics Geosciences Multidisciplinary Meteorology & Atmospheric Sciences Geology INTERPLANETARY MAGNETIC-FIELD SMALL-SCALE IRREGULARITIES LATITUDE F-REGION SUN-ALIGNED ARCS POLAR-CAP ELECTRIC-FIELD NORTHWARD CONVECTION PATTERNS TIMES |
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 |
Other Non-Article Part of 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 |
publishDate |
1997 |
url |
https://figshare.com/articles/journal_contribution/A_comparison_of_optical_and_coherent_HF_radar_backscatter_observations_of_a_post-midnight_aurora/10115297 |
geographic |
Svalbard Ny-Ålesund |
geographic_facet |
Svalbard Ny-Ålesund |
genre |
Ny Ålesund Ny-Ålesund Svalbard |
genre_facet |
Ny Ålesund Ny-Ålesund Svalbard |
op_relation |
2381/19757 https://figshare.com/articles/journal_contribution/A_comparison_of_optical_and_coherent_HF_radar_backscatter_observations_of_a_post-midnight_aurora/10115297 |
op_rights |
All Rights Reserved |
_version_ |
1766154548256178176 |