On temperature in line-gap regions

The small regions in the photosphere where many absorption lines weaken have been investigated by several authors. Sheeley attempted to explain the weakening of neutral lines in terms of a temperature increase on the basis of a simple theoretical model. It is shown that this model is not applicable but that a modified theory is able to interpret the observed behaviour of both neutral and ionized lines in terms of a temperature increase of a few percent.Mitteilungen aus dem Fraunhofer Institut, Nr. 98.