Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes

Radio-bright regions near the solar poles are frequently observed in Nobeyama Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal holes. However, the origin of these polar brightenings has not been established yet. We propose that small magnetic loops are the source of these...

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Detalles Bibliográficos
Publicado: 2017
Materias:
Sun: chromosphere
Sun: general
Sun: radio radiation
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v851_n2_p_Selhorst
http://hdl.handle.net/20.500.12110/paper_0004637X_v851_n2_p_Selhorst
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_0004637X_v851_n2_p_Selhorst
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spelling paper:paper_0004637X_v851_n2_p_Selhorst2023-06-08T14:29:20Z Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes Sun: chromosphere Sun: general Sun: radio radiation Radio-bright regions near the solar poles are frequently observed in Nobeyama Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal holes. However, the origin of these polar brightenings has not been established yet. We propose that small magnetic loops are the source of these bright patches, and present modeling results that reproduce the main observational characteristics of the polar brightening within coronal holes at 17 GHz. The simulations were carried out by calculating the radio emission of the small loops, with several temperature and density profiles, within a 2D coronal hole atmospheric model. If located at high latitudes, the size of the simulated bright patches are much smaller than that of the beam size and they present the instrument beam size when observed. The larger bright patches can be generated by a great number of small magnetic loops unresolved by the NoRH beam. Loop models that reproduce bright patches contain denser and hotter plasma near the upper chromosphere and lower corona. On the other hand, loops with increased plasma density and temperature only in the corona do not contribute to the emission at 17 GHz. This could explain the absence of a one-to-one association between the 17 GHz bright patches and those observed in extreme ultraviolet. Moreover, the emission arising from small magnetic loops located close to the limb may merge with the usual limb brightening profile, increasing its brightness temperature and width. © 2017. The American Astronomical Society. All rights reserved. 2017 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v851_n2_p_Selhorst http://hdl.handle.net/20.500.12110/paper_0004637X_v851_n2_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: radio radiation
spellingShingle Sun: chromosphere
Sun: general
Sun: radio radiation
Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
topic_facet Sun: chromosphere
Sun: general
Sun: radio radiation
description Radio-bright regions near the solar poles are frequently observed in Nobeyama Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal holes. However, the origin of these polar brightenings has not been established yet. We propose that small magnetic loops are the source of these bright patches, and present modeling results that reproduce the main observational characteristics of the polar brightening within coronal holes at 17 GHz. The simulations were carried out by calculating the radio emission of the small loops, with several temperature and density profiles, within a 2D coronal hole atmospheric model. If located at high latitudes, the size of the simulated bright patches are much smaller than that of the beam size and they present the instrument beam size when observed. The larger bright patches can be generated by a great number of small magnetic loops unresolved by the NoRH beam. Loop models that reproduce bright patches contain denser and hotter plasma near the upper chromosphere and lower corona. On the other hand, loops with increased plasma density and temperature only in the corona do not contribute to the emission at 17 GHz. This could explain the absence of a one-to-one association between the 17 GHz bright patches and those observed in extreme ultraviolet. Moreover, the emission arising from small magnetic loops located close to the limb may merge with the usual limb brightening profile, increasing its brightness temperature and width. © 2017. The American Astronomical Society. All rights reserved.
title Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
title_short Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
title_full Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
title_fullStr Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
title_full_unstemmed Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
title_sort association of radio polar cap brightening with bright patches and coronal holes
publishDate 2017
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v851_n2_p_Selhorst
http://hdl.handle.net/20.500.12110/paper_0004637X_v851_n2_p_Selhorst
_version_ 1768543973083709440

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