Spectra of Solar Activity Regions

Abstract

From the brilliant lecture of Professor Minnaert we have learned how poor our knowledge is of the physical state of the undisturbed quiet solar atmosphere. But if we turn our attention to the phenomena of solar activity the position is still worse because only during the two past decades we accumulated more or less systematically important spectroscopic data about the processes in solar active regions, and yet we are very far from a clear understanding of the physical nature of these processes.