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Association of radio polar cap brightening with bright patches and coronal holes by C. L. Selhorst et al.*

20 Mar 2018, 10:01 UTC
Association of radio polar cap brightening with bright patches and coronal holes  by C. L. Selhorst et al.*
(200 words excerpt, click title or image to see full post)

The purpose of this work is to model the emission of 17 GHz polar bright patches, which are frequently observed by the Nobeyama Radioheliograph (NoRH) in association with coronal holes. Although these bright regions have been observed for a few decades, their nature remains unclear. Our simulations were based on the temperature and density profiles from the SSC atmospheric model (Selhorst et al., 2005), with modifications to include a coronal hole atmospheric model and magnetic loops as the sources of the radio bright patches.
We calculated the radio emission at 17 GHz from coronal holes, in comparison with typical quiet Sun regions. As expected, in a static atmosphere, the lower temperature and density atmosphere inside a coronal hole resulted in lower brightness temperature values. Our results show, however, that the presence of spicules (spatially unresolved by NoRH) can produce brighter regions than what would be expected from coronal holes. To simulate the bright patches, we introduced small magnetic loops, with hotter and denser plasma than its surroundings – see Figure 1. We find that the radio emission from smaller loops (5.0 Mm of radius) comes from the top of the loop, while the emission from larger loops (7.5 Mm of ...

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