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Shapes and centre-to-limb variation of the H and K lines in sunspot umbrae

✍ Scribed by R. B. Teplitskaja; N. M. Firstova


Publisher
Springer
Year
1976
Tongue
English
Weight
614 KB
Volume
48
Category
Article
ISSN
0038-0938

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✦ Synopsis


The shapes of the Ca ii H and K lines in sunspot umbral spectra vary from single asymmetric peaks near the centre of the disk to almost symmetric double peaks at the limb. In addition, there are other differences in the behaviour of both H and K lines in sunspots compared to the quiet Sun. The whole complex of the phenomena observed can not be explained by large scale chromosphere motions. Instead, a satisfactory model reproducing in detail peculiarities of the umbral emission reversals contains a cloud of emitting and absorbing gas located above the chromosphere, which flows into the sunspot. The radiation field parameters in such a cloud are consistent with the concept of weak quiescent prominences above the umbra.


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