On the intensity thresholds of the network and plage regions

Abstract

A period of minimum solar activity in April and May 1996 was used to analyze full-disk Ca K spectroheliograms with the aim of deriving the intensity thresholds of the quiet network and the plages by applying the so-called inflexion point method. The average network intensity threshold is found to be influenced mainly by the seeing, whereas the average plage threshold shows an increasing trend from disk center towards the solar limb. Both parameters are compared with the results of other authors.