Vistas on Stellar?Solar Atmospheres

Abstract

The evolution of the modelling of the stellar atmosphere towards greater physical consistency is described briefly. The progressive relaxation of stringent hypotheses (such as RE, L TE, HE, plane-parallel geometry) in all layers characterizes this evolution. We discuss roughness (i.e. departures from sphericaI geometry), the origin of the concept, and how its recent application to Skylab and OSO-8 UV data shows its importance, difficult to take into account accurately, but not to be overlooked. In the last part of the paper we argue for a general overall coupling between mechanisms which characterize the stellar-solar machinery described.