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 50 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 b...

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Autores principales: Selhorst, C.L., Simoes, P.J.A., Brajša, R., Valio, A., De Castro, C.G.G., Costa, J.E.R., Menezes, F., Rozelot, J.P., Hales, A.S., Iwai, K., White, S.
Formato: JOUR
Materias:
Sun: chromosphere
Sun: general
Sun: photosphere
Sun: radio radiation
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_0004637X_v871_n1_p_Selhorst
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_0004637X_v871_n1_p_Selhorst
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spelling todo:paper_0004637X_v871_n1_p_Selhorst2023-10-03T14:02:46Z Solar Polar Brightening and Radius at 100 and 230 GHz Observed by ALMA Selhorst, C.L. Simoes, P.J.A. Brajša, R. Valio, A. De Castro, C.G.G. Costa, J.E.R. Menezes, F. Rozelot, J.P. Hales, A.S. Iwai, K. White, S. Sun: chromosphere Sun: general Sun: photosphere Sun: radio radiation Polar brightening of the Sun at radio frequencies has been studied for almost 50 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 brightening emission for two semi-empirical atmospheric models, FAL-C and SSC. Both models presented larger limb intensities than the average 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. © 2019. The American Astronomical Society. All rights reserved.. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_0004637X_v871_n1_p_Selhorst
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Sun: chromosphere
Sun: general
Sun: photosphere
Sun: radio radiation
spellingShingle Sun: chromosphere
Sun: general
Sun: photosphere
Sun: radio radiation
Selhorst, C.L.
Simoes, P.J.A.
Brajša, R.
Valio, A.
De Castro, C.G.G.
Costa, J.E.R.
Menezes, F.
Rozelot, J.P.
Hales, A.S.
Iwai, K.
White, S.
Solar Polar Brightening and Radius at 100 and 230 GHz Observed by ALMA
topic_facet Sun: chromosphere
Sun: general
Sun: photosphere
Sun: radio radiation
description Polar brightening of the Sun at radio frequencies has been studied for almost 50 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 brightening emission for two semi-empirical atmospheric models, FAL-C and SSC. Both models presented larger limb intensities than the average 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. © 2019. The American Astronomical Society. All rights reserved..
format JOUR
author Selhorst, C.L.
Simoes, P.J.A.
Brajša, R.
Valio, A.
De Castro, C.G.G.
Costa, J.E.R.
Menezes, F.
Rozelot, J.P.
Hales, A.S.
Iwai, K.
White, S.
author_facet Selhorst, C.L.
Simoes, P.J.A.
Brajša, R.
Valio, A.
De Castro, C.G.G.
Costa, J.E.R.
Menezes, F.
Rozelot, J.P.
Hales, A.S.
Iwai, K.
White, S.
author_sort Selhorst, C.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
url http://hdl.handle.net/20.500.12110/paper_0004637X_v871_n1_p_Selhorst
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