A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora
International audience 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-expandi...
Main Authors: | , , |
---|---|
Other Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
1997
|
Subjects: | |
Online Access: | https://hal.science/hal-00316496 https://hal.science/hal-00316496/document https://hal.science/hal-00316496/file/angeo-15-1388-1997.pdf |
id |
ftinsu:oai:HAL:hal-00316496v1 |
---|---|
record_format |
openpolar |
spelling |
ftinsu:oai:HAL:hal-00316496v1 2023-11-12T04:23:34+01:00 A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora Milan, S. E. Lester, M. Moen, J. Department of Physics and Astronomy Leicester University of Leicester UNIS UniS 1997 https://hal.science/hal-00316496 https://hal.science/hal-00316496/document https://hal.science/hal-00316496/file/angeo-15-1388-1997.pdf en eng HAL CCSD European Geosciences Union hal-00316496 https://hal.science/hal-00316496 https://hal.science/hal-00316496/document https://hal.science/hal-00316496/file/angeo-15-1388-1997.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316496 Annales Geophysicae, 1997, 15 (11), pp.1388-1398 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/article Journal articles 1997 ftinsu 2023-10-25T16:25:36Z International audience 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 Institut national des sciences de l'Univers: HAL-INSU Ny-Ålesund Svalbard |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences Milan, S. E. Lester, M. Moen, J. A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience 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. |
author2 |
Department of Physics and Astronomy Leicester University of Leicester UNIS UniS |
format |
Article in Journal/Newspaper |
author |
Milan, S. E. Lester, M. Moen, J. |
author_facet |
Milan, S. E. Lester, M. Moen, J. |
author_sort |
Milan, S. E. |
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 |
HAL CCSD |
publishDate |
1997 |
url |
https://hal.science/hal-00316496 https://hal.science/hal-00316496/document https://hal.science/hal-00316496/file/angeo-15-1388-1997.pdf |
geographic |
Ny-Ålesund Svalbard |
geographic_facet |
Ny-Ålesund Svalbard |
genre |
Ny Ålesund Ny-Ålesund Svalbard |
genre_facet |
Ny Ålesund Ny-Ålesund Svalbard |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00316496 Annales Geophysicae, 1997, 15 (11), pp.1388-1398 |
op_relation |
hal-00316496 https://hal.science/hal-00316496 https://hal.science/hal-00316496/document https://hal.science/hal-00316496/file/angeo-15-1388-1997.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782338284568969216 |