S-component model computations applied to mean mm-wave measurements

Abstract

Selected mm-wave observations with arc-min resolution of active regions in the central part of the solar disk obtained by the Metsahovi Radio Research Station during the years 1978–1984 are discussed from the perspective of recently developed mean S-component models. It is concluded that the mm-wave emission has a considerable (but at present unresolved) spatial fine structure. Compatibility with optical and EUV observations is only achieved by the assumption of embedding of bright plage elements in a quasi-quiet background according to filling factors of less than about 5% in the mm-wave range. Basing on model calculations, predictions are made concerning the mm-wave brightness of the sunspot and plage components. Averaging over the whole S-component sources provides a good correspondence between observation and calculation. The necessary elimination of well identified burst sources (15% of cases) and of a group of further unspecified small-scale sources (30%) from the above material indicates a greater contribution of ‘hot-temperature’ radiation to the mean emission from solar active regions at mm-wavelengths than had formerly been expected.