𝔖 Bobbio Scriptorium
✦   LIBER   ✦

On the center-to-limb variation of sunspot brightness

✍ Scribed by W. Mattig

Publisher
Springer
Year
1969
Tongue
English
Weight
232 KB
Volume
6
Category
Article
ISSN
0038-0938

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✦ Synopsis

A preliminary analysis of recent measurements of the brightness ratio spot-photosphere of various authors leads to the result, that the limb-darkening of the umbra is considerably less than that of the photosphere. The small value of the center-to-limb variation implies a very small temperature gradient, which is, for optical depths r~.0.2, about one order of magnitude smaller than previously thought (Figure 3). This result would seem to rule out radiative equilibrium in the deeper layers (rT~. 0.2) of sunspot umbrae.

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