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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

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

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Selhorst, Caius L. [1] ; Simoes, Paulo J. A. [2] ; Oliveira e Silva, Alexandre J. [3] ; Gimenez de Castro, C. G. [4, 5] ; Costa, Joaquim E. R. [6] ; Valio, Adriana [5]
Total Authors: 6
[1] Univ Cruzeiro Sul, NAT, Sao Paulo, SP - Brazil
[2] Univ Glasgow, Sch Phys & Astron, SUPA, Glasgow G12 8QQ, Lanark - Scotland
[3] Univ Vale Paraba Univ, IP&D, Sao Jose Dos Campos, SP - Brazil
[4] Univ Buenos Aires, CONICET, IAFE, Buenos Aires, DF - Argentina
[5] Univ Presbiteriana Mackenzie, CRAAM, BR-01302907 Sao Paulo, SP - Brazil
[6] Inst Nacl Pesquisas Espaciais, CEA, Sao Jose Dos Campos, SP - Brazil
Total Affiliations: 6
Document type: Journal article
Source: ASTROPHYSICAL JOURNAL; v. 851, n. 2 DEC 20 2017.
Web of Science Citations: 2

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. (AU)

FAPESP's process: 14/10489-0 - Study of the changes in the solar magnetic field based on radio observations
Grantee:Caius Lucius Selhorst
Support type: Regular Research Grants