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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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_0004637X_v851_n2_p_Selhorst |
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todo:paper_0004637X_v851_n2_p_Selhorst2023-10-03T14:02:44Z Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes Selhorst, C.L. Simões, P.J.A. Silva, A.J.O.E. Castro, C.G.G.D. Costa, J.E.R. Valio, A. 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. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar 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 Selhorst, C.L. Simões, P.J.A. Silva, A.J.O.E. Castro, C.G.G.D. Costa, J.E.R. Valio, A. 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. |
| format |
JOUR |
| author |
Selhorst, C.L. Simões, P.J.A. Silva, A.J.O.E. Castro, C.G.G.D. Costa, J.E.R. Valio, A. |
| author_facet |
Selhorst, C.L. Simões, P.J.A. Silva, A.J.O.E. Castro, C.G.G.D. Costa, J.E.R. Valio, A. |
| author_sort |
Selhorst, C.L. |
| 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 |
| url |
http://hdl.handle.net/20.500.12110/paper_0004637X_v851_n2_p_Selhorst |
| work_keys_str_mv |
AT selhorstcl associationofradiopolarcapbrighteningwithbrightpatchesandcoronalholes AT simoespja associationofradiopolarcapbrighteningwithbrightpatchesandcoronalholes AT silvaajoe associationofradiopolarcapbrighteningwithbrightpatchesandcoronalholes AT castrocggd associationofradiopolarcapbrighteningwithbrightpatchesandcoronalholes AT costajer associationofradiopolarcapbrighteningwithbrightpatchesandcoronalholes AT valioa associationofradiopolarcapbrighteningwithbrightpatchesandcoronalholes |
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