Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica
Polar cap absorption (PCA) events recorded during November 2001 are investigated by observations of ionospheric absorption of a 30MHz riometer installed at Terra Nova Bay (Antarctica), and of solar proton flux, monitored by the NOAA-GOES8 satellite in geo-synchronous orbit. During this period three...
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ftdoajarticles:oai:doaj.org/article:cb4887970c484527babeae4c5ba94502 2023-05-15T13:52:47+02:00 Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica L. Perrone L. Alfonsi V. Romano G. de Franceschi 2004-04-01T00:00:00Z https://doi.org/10.5194/angeo-22-1633-2004 https://doaj.org/article/cb4887970c484527babeae4c5ba94502 EN eng Copernicus Publications https://www.ann-geophys.net/22/1633/2004/angeo-22-1633-2004.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-22-1633-2004 0992-7689 1432-0576 https://doaj.org/article/cb4887970c484527babeae4c5ba94502 Annales Geophysicae, Vol 22, Pp 1633-1648 (2004) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2004 ftdoajarticles https://doi.org/10.5194/angeo-22-1633-2004 2022-12-30T21:25:12Z Polar cap absorption (PCA) events recorded during November 2001 are investigated by observations of ionospheric absorption of a 30MHz riometer installed at Terra Nova Bay (Antarctica), and of solar proton flux, monitored by the NOAA-GOES8 satellite in geo-synchronous orbit. During this period three solar proton events (SPE) on 4, 19 and 23 November occurred. Two of these are among the dozen most intense events since 1954 and during the current solar cycle (23rd), the event of 4 November shows the greatest proton flux at energies >10MeV. Many factors contribute to the peak intensity of the two SPE biggest events, one is the Coronal Mass Ejection (CME) speed, other factors are the ambient population of SPE and the shock front due to the CME. During these events absorption peaks of several dB (~20dB) are observed at Terra Nova Bay, tens of minutes after the impact of fast halo CMEs on the geomagnetic field. Results of a cross-correlation analysis show that the first hour of absorption is mainly produced by 84–500MeV protons in the case of the 4 November event and by 15–44MeV protons for the event of 23 November, whereas in the entire event the contribution to the absorption is due chiefly to 4.2–82MeV (4 November) and by 4.2–14.5MeV (23 November). Good agreement is generally obtained between observed and calculated absorption by the empirical flux-absorption relationship for threshold energy E 0 =10MeV. From the residuals one can argue that other factors (e.g. X-ray increases and geomagnetic disturbances) can contribute to the ionospheric absorption. Key words. Ionosphere (Polar Ionosphere, Particle precipitation) – Solar physics (Flares and mass ejections) Article in Journal/Newspaper Antarc* Antarctica Directory of Open Access Journals: DOAJ Articles Terra Nova Bay Annales Geophysicae 22 5 1633 1648 |
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 L. Perrone L. Alfonsi V. Romano G. de Franceschi Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
Polar cap absorption (PCA) events recorded during November 2001 are investigated by observations of ionospheric absorption of a 30MHz riometer installed at Terra Nova Bay (Antarctica), and of solar proton flux, monitored by the NOAA-GOES8 satellite in geo-synchronous orbit. During this period three solar proton events (SPE) on 4, 19 and 23 November occurred. Two of these are among the dozen most intense events since 1954 and during the current solar cycle (23rd), the event of 4 November shows the greatest proton flux at energies >10MeV. Many factors contribute to the peak intensity of the two SPE biggest events, one is the Coronal Mass Ejection (CME) speed, other factors are the ambient population of SPE and the shock front due to the CME. During these events absorption peaks of several dB (~20dB) are observed at Terra Nova Bay, tens of minutes after the impact of fast halo CMEs on the geomagnetic field. Results of a cross-correlation analysis show that the first hour of absorption is mainly produced by 84–500MeV protons in the case of the 4 November event and by 15–44MeV protons for the event of 23 November, whereas in the entire event the contribution to the absorption is due chiefly to 4.2–82MeV (4 November) and by 4.2–14.5MeV (23 November). Good agreement is generally obtained between observed and calculated absorption by the empirical flux-absorption relationship for threshold energy E 0 =10MeV. From the residuals one can argue that other factors (e.g. X-ray increases and geomagnetic disturbances) can contribute to the ionospheric absorption. Key words. Ionosphere (Polar Ionosphere, Particle precipitation) – Solar physics (Flares and mass ejections) |
format |
Article in Journal/Newspaper |
author |
L. Perrone L. Alfonsi V. Romano G. de Franceschi |
author_facet |
L. Perrone L. Alfonsi V. Romano G. de Franceschi |
author_sort |
L. Perrone |
title |
Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica |
title_short |
Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica |
title_full |
Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica |
title_fullStr |
Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica |
title_full_unstemmed |
Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica |
title_sort |
polar cap absorption events of november 2001 at terra nova bay, antarctica |
publisher |
Copernicus Publications |
publishDate |
2004 |
url |
https://doi.org/10.5194/angeo-22-1633-2004 https://doaj.org/article/cb4887970c484527babeae4c5ba94502 |
geographic |
Terra Nova Bay |
geographic_facet |
Terra Nova Bay |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_source |
Annales Geophysicae, Vol 22, Pp 1633-1648 (2004) |
op_relation |
https://www.ann-geophys.net/22/1633/2004/angeo-22-1633-2004.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-22-1633-2004 0992-7689 1432-0576 https://doaj.org/article/cb4887970c484527babeae4c5ba94502 |
op_doi |
https://doi.org/10.5194/angeo-22-1633-2004 |
container_title |
Annales Geophysicae |
container_volume |
22 |
container_issue |
5 |
container_start_page |
1633 |
op_container_end_page |
1648 |
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1766257480717828096 |