Large-scale patterns on the Sun observed in the millimetric wavelength range

Abstract

The nature and behaviour of large-scale patterns on the solar surface, indicated by the areas of brightness-temperature depressions in the millimetric wavelength range, is studied. A large sample of 346 individual, low-temperature regions (LTRs) was employed to provide reliable statistical evidence. An association of 99% was found between the locations of LTRs and the large-scale magnetic field inversion lines, and 60% of the LTRs were associated with the inversion line filaments. A tentative physical association with filaments is reconsidered, and one particularly well-observed case is presented. The heights of the perturbers causing brightness-temperature depressions are discussed. The long-term evolution of the latitudinal distribution of LTRs is presented in a butterfly diagram. Two belts of low-temperature regions outline the active region belts, shifting with them towards the equator during the solar activity cycle. The low-temperature region belts of the forthcoming cycle appear already at the maximum of the actual cycle at latitudes of about 55 °. The superpositions of the temperature minima distributions in the synoptic maps show patterns appearing as ‘giant cells’ and compatible with indications inferred from magnetographic data. The reliability of the inferred cells is considered, and a statistical analysis reveals a negligible probability for an accidental distribution appearing in the form of giant cells.