Solar polar brightening and radius at 100 and 230 GHz observed by ALMA
Polar brightening of the Sun at radio frequencies has been studied for almost fifty years and yet a disagreement persists between solar atmospheric models and observations. Some observations reported brightening values much smaller than the expected values obtained from the models, with discrepancie...
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ftuglasgow:oai:eprints.gla.ac.uk:174513 2024-05-19T07:48:40+00:00 Solar polar brightening and radius at 100 and 230 GHz observed by ALMA Selhorst, Caius L. Simoes, Paulo J.A. Brajša, Roman Valio, Adriana Giménez de Castro, C.G. Costa, Joaquim E.R. Menezes, Fabian Rozelot, Jean Pierre Hales, Antonio S. Iwai, Kazumasa White, Stephen 2019-01-21 text https://eprints.gla.ac.uk/174513/ https://eprints.gla.ac.uk/174513/7/174513.pdf en eng American Astronomical Society https://eprints.gla.ac.uk/174513/7/174513.pdf Selhorst, C. L. et al. (2019) Solar polar brightening and radius at 100 and 230 GHz observed by ALMA. Astrophysical Journal <https://eprints.gla.ac.uk/view/journal_volume/Astrophysical_Journal.html>, 871(1), 45. (doi:10.3847/1538-4357/aaf4f2 <https://doi.org/10.3847/1538-4357/aaf4f2>) Articles PeerReviewed 2019 ftuglasgow https://doi.org/10.3847/1538-4357/aaf4f2 2024-05-01T14:03:38Z Polar brightening of the Sun at radio frequencies has been studied for almost fifty years and yet a disagreement persists between solar atmospheric models and observations. Some observations reported brightening values much smaller than the expected values obtained from the models, with discrepancies being particularly large at millimeter wavelengths. New clues to calibrate the atmospheric models can be obtained with the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) radio interferometer. In this work, we analyzed the lower limit of the polar brightening observed at 100 and 230 GHz by ALMA, during its Science Verification period, 2015 December 16-20. We find that the average polar intensity is higher than the disk intensity at 100 and 230 GHz, with larger brightness intensities at the South pole in eight of the nine maps analyzed. The observational results were compared with calculations of the millimetric limb brightnening emission for two semi-empirical atmospheric models, FAL- C (Fontenla et al. 1993) and SSC (Selhorst et al. 2005a). Both models presented larger limb intensities than the averaged observed values. The intensities obtained with the SSC model were closer to the observations, with polar brightenings of 10.5% and 17.8% at 100 and 230 GHz, respectively. This discrepancy may be due to the presence of chromospheric features (like spicules) at regions close to the limb. Article in Journal/Newspaper South pole University of Glasgow: Enlighten - Publications The Astrophysical Journal 871 1 45 |
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Open Polar |
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University of Glasgow: Enlighten - Publications |
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ftuglasgow |
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English |
description |
Polar brightening of the Sun at radio frequencies has been studied for almost fifty years and yet a disagreement persists between solar atmospheric models and observations. Some observations reported brightening values much smaller than the expected values obtained from the models, with discrepancies being particularly large at millimeter wavelengths. New clues to calibrate the atmospheric models can be obtained with the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) radio interferometer. In this work, we analyzed the lower limit of the polar brightening observed at 100 and 230 GHz by ALMA, during its Science Verification period, 2015 December 16-20. We find that the average polar intensity is higher than the disk intensity at 100 and 230 GHz, with larger brightness intensities at the South pole in eight of the nine maps analyzed. The observational results were compared with calculations of the millimetric limb brightnening emission for two semi-empirical atmospheric models, FAL- C (Fontenla et al. 1993) and SSC (Selhorst et al. 2005a). Both models presented larger limb intensities than the averaged observed values. The intensities obtained with the SSC model were closer to the observations, with polar brightenings of 10.5% and 17.8% at 100 and 230 GHz, respectively. This discrepancy may be due to the presence of chromospheric features (like spicules) at regions close to the limb. |
format |
Article in Journal/Newspaper |
author |
Selhorst, Caius L. Simoes, Paulo J.A. Brajša, Roman Valio, Adriana Giménez de Castro, C.G. Costa, Joaquim E.R. Menezes, Fabian Rozelot, Jean Pierre Hales, Antonio S. Iwai, Kazumasa White, Stephen |
spellingShingle |
Selhorst, Caius L. Simoes, Paulo J.A. Brajša, Roman Valio, Adriana Giménez de Castro, C.G. Costa, Joaquim E.R. Menezes, Fabian Rozelot, Jean Pierre Hales, Antonio S. Iwai, Kazumasa White, Stephen Solar polar brightening and radius at 100 and 230 GHz observed by ALMA |
author_facet |
Selhorst, Caius L. Simoes, Paulo J.A. Brajša, Roman Valio, Adriana Giménez de Castro, C.G. Costa, Joaquim E.R. Menezes, Fabian Rozelot, Jean Pierre Hales, Antonio S. Iwai, Kazumasa White, Stephen |
author_sort |
Selhorst, Caius L. |
title |
Solar polar brightening and radius at 100 and 230 GHz observed by ALMA |
title_short |
Solar polar brightening and radius at 100 and 230 GHz observed by ALMA |
title_full |
Solar polar brightening and radius at 100 and 230 GHz observed by ALMA |
title_fullStr |
Solar polar brightening and radius at 100 and 230 GHz observed by ALMA |
title_full_unstemmed |
Solar polar brightening and radius at 100 and 230 GHz observed by ALMA |
title_sort |
solar polar brightening and radius at 100 and 230 ghz observed by alma |
publisher |
American Astronomical Society |
publishDate |
2019 |
url |
https://eprints.gla.ac.uk/174513/ https://eprints.gla.ac.uk/174513/7/174513.pdf |
genre |
South pole |
genre_facet |
South pole |
op_relation |
https://eprints.gla.ac.uk/174513/7/174513.pdf Selhorst, C. L. et al. (2019) Solar polar brightening and radius at 100 and 230 GHz observed by ALMA. Astrophysical Journal <https://eprints.gla.ac.uk/view/journal_volume/Astrophysical_Journal.html>, 871(1), 45. (doi:10.3847/1538-4357/aaf4f2 <https://doi.org/10.3847/1538-4357/aaf4f2>) |
op_doi |
https://doi.org/10.3847/1538-4357/aaf4f2 |
container_title |
The Astrophysical Journal |
container_volume |
871 |
container_issue |
1 |
container_start_page |
45 |
_version_ |
1799466978192130048 |