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Limb-darkening and solar cycle variation of sunspot intensities

✍ Scribed by F. Albregtsen; P. B. Jorås; P. Maltby

Publisher
Springer
Year
1984
Tongue
English
Weight
677 KB
Volume
90
Category
Article
ISSN
0038-0938

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✦ Synopsis

New observations of the umbral limb-darkening are presented. We find a real and significant decrease in the umbra/photosphere intensity ratio towards the limb. This result contrasts the findings of previous authors and we believe this to be the first time such a decrease is reported. Our conclusion is based on broad band pinhole photometer intensity observations of 22 large sunspots covering the spectral region 0.387-2.35 ~tm. The data are selected from measurements on approximately 600 days during the last 15.5 yr. The application of the limb-darkening data to the study of the temperature stratification in the umbra is briefly discussed. The observations confirm the suggestion that the umbra/photosphere intensity ratio seems to be a linear function of the phase in the solar cycle.

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