High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica
A small, 54 MHz wind-profiler radar, MARA, was operated at Troll, Antarctica (72° S, 2.5° E), continuously from November 2011 to January 2014, covering two complete Antarctic winters. Despite very low power, MARA observed echoes from heights of 55–80 km (polar mesosphere winter echoes, PMWE) on 60%...
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ftdoajarticles:oai:doaj.org/article:27e8b6cbc3cf4ad7ab2cb635dad077bd 2023-05-15T13:39:16+02:00 High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica S. Kirkwood A. Osepian E. Belova Y.-S. Lee 2015-06-01T00:00:00Z https://doi.org/10.5194/angeo-33-609-2015 https://doaj.org/article/27e8b6cbc3cf4ad7ab2cb635dad077bd EN eng Copernicus Publications https://www.ann-geophys.net/33/609/2015/angeo-33-609-2015.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-33-609-2015 0992-7689 1432-0576 https://doaj.org/article/27e8b6cbc3cf4ad7ab2cb635dad077bd Annales Geophysicae, Vol 33, Pp 609-622 (2015) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2015 ftdoajarticles https://doi.org/10.5194/angeo-33-609-2015 2022-12-31T09:36:38Z A small, 54 MHz wind-profiler radar, MARA, was operated at Troll, Antarctica (72° S, 2.5° E), continuously from November 2011 to January 2014, covering two complete Antarctic winters. Despite very low power, MARA observed echoes from heights of 55–80 km (polar mesosphere winter echoes, PMWE) on 60% of all winter days (from March to October). This contrasts with previous reports from radars at high northern latitudes, where PWME have been reported only by very high power radars or during rare periods of unusually high electron density at PMWE heights, such as during solar proton events. Analysis shows that PWME at Troll were not related to solar proton events but were often closely related to the arrival of high-speed solar wind streams (HSS) at the Earth, with PWME appearing at heights as low as 56 km and persisting for up to 15 days following HSS arrival. This demonstrates that HSS effects penetrate directly to below 60 km height in the polar atmosphere. Using local observations of cosmic-noise absorption (CNA), a theoretical ionization/ion-chemistry model and a statistical model of precipitating energetic electrons associated with HSS, the electron density conditions during the HSS events are estimated. We find that PMWE detectability cannot be explained by these variations in electron density and molecular-ion chemistry alone. PWME become detectable at different thresholds depending on solar illumination and height. In darkness, PWME are detected only when the modelled electron density is above a threshold of about 1000 cm −3 , and only above 75 km height, where negative ions are few. In daylight, the electron density threshold falls by at least 2 orders of magnitude and PWME are found primarily below 75 km height, even in conditions when a large proportion of negative ions is expected. There is also a strong dawn–dusk asymmetry with PWME detected very rarely during morning twilight but often during evening twilight. This behaviour cannot be explained if PMWE are caused by small-scale structure in the ... Article in Journal/Newspaper Antarc* Antarctic Antarctica Directory of Open Access Journals: DOAJ Articles Antarctic Mara ENVELOPE(132.133,132.133,62.267,62.267) Troll ENVELOPE(2.534,2.534,-72.002,-72.002) Annales Geophysicae 33 6 609 622 |
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. Kirkwood A. Osepian E. Belova Y.-S. Lee High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
A small, 54 MHz wind-profiler radar, MARA, was operated at Troll, Antarctica (72° S, 2.5° E), continuously from November 2011 to January 2014, covering two complete Antarctic winters. Despite very low power, MARA observed echoes from heights of 55–80 km (polar mesosphere winter echoes, PMWE) on 60% of all winter days (from March to October). This contrasts with previous reports from radars at high northern latitudes, where PWME have been reported only by very high power radars or during rare periods of unusually high electron density at PMWE heights, such as during solar proton events. Analysis shows that PWME at Troll were not related to solar proton events but were often closely related to the arrival of high-speed solar wind streams (HSS) at the Earth, with PWME appearing at heights as low as 56 km and persisting for up to 15 days following HSS arrival. This demonstrates that HSS effects penetrate directly to below 60 km height in the polar atmosphere. Using local observations of cosmic-noise absorption (CNA), a theoretical ionization/ion-chemistry model and a statistical model of precipitating energetic electrons associated with HSS, the electron density conditions during the HSS events are estimated. We find that PMWE detectability cannot be explained by these variations in electron density and molecular-ion chemistry alone. PWME become detectable at different thresholds depending on solar illumination and height. In darkness, PWME are detected only when the modelled electron density is above a threshold of about 1000 cm −3 , and only above 75 km height, where negative ions are few. In daylight, the electron density threshold falls by at least 2 orders of magnitude and PWME are found primarily below 75 km height, even in conditions when a large proportion of negative ions is expected. There is also a strong dawn–dusk asymmetry with PWME detected very rarely during morning twilight but often during evening twilight. This behaviour cannot be explained if PMWE are caused by small-scale structure in the ... |
format |
Article in Journal/Newspaper |
author |
S. Kirkwood A. Osepian E. Belova Y.-S. Lee |
author_facet |
S. Kirkwood A. Osepian E. Belova Y.-S. Lee |
author_sort |
S. Kirkwood |
title |
High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica |
title_short |
High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica |
title_full |
High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica |
title_fullStr |
High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica |
title_full_unstemmed |
High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica |
title_sort |
high-speed solar wind streams and polar mesosphere winter echoes at troll, antarctica |
publisher |
Copernicus Publications |
publishDate |
2015 |
url |
https://doi.org/10.5194/angeo-33-609-2015 https://doaj.org/article/27e8b6cbc3cf4ad7ab2cb635dad077bd |
long_lat |
ENVELOPE(132.133,132.133,62.267,62.267) ENVELOPE(2.534,2.534,-72.002,-72.002) |
geographic |
Antarctic Mara Troll |
geographic_facet |
Antarctic Mara Troll |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_source |
Annales Geophysicae, Vol 33, Pp 609-622 (2015) |
op_relation |
https://www.ann-geophys.net/33/609/2015/angeo-33-609-2015.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-33-609-2015 0992-7689 1432-0576 https://doaj.org/article/27e8b6cbc3cf4ad7ab2cb635dad077bd |
op_doi |
https://doi.org/10.5194/angeo-33-609-2015 |
container_title |
Annales Geophysicae |
container_volume |
33 |
container_issue |
6 |
container_start_page |
609 |
op_container_end_page |
622 |
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1766116643751067648 |