Large-Scale Magnetic Fields and Activity Patterns on the Sun

Abstract

The recent results concerning the large-scale magnetic field and solar activity distribution are summarized. The static characteristics for three types of such large-scale features are given: (a) Giant regular structures (super-supergranules) are probably the largest elements in the hierarchy of solar convective cells, which can be defined in the solar atmosphere for example, by magnetic field patterns, faculae, calcium flocculi, and the organization of active regions. (b) Active longitudes are the longitude sectors with grouped activity and concentrated magnetic fields. The grouping lasts in the same sector for many successive rotations. These active longitudes may have different rates of shift in heliographic longitude per rotation in a given system of coordinates. They are demonstrated not only on magnetic synoptic charts arranged by latitude zones but may also be followed on Zurich Heliographic Maps of the Photosphere for at least four cycles. This means that the organization of activity and fields in streams or active longitudes does not change during several tens of years and proceeds in the same way following the same rules of development, (c) Active latitudes may also play a role in the formation of large-scale patterns.

The dynamics of large-scale features is presented. The active longitudes develop as consecutive complexes of activity which are separate impulses of activity, being usually in opposite phase if two longitudes are active. Giant regular structures develop analogously to supergranules or granules if the background magnetic field in the active longitude reaches a certain level. A possible theoretical explanation of the formation of large-scale patterns, including the ‘influence of the planets’ is discussed.

The sun as a star and the manifestation of longitudinal and latitudinal distributions of the solar magnetic field in the interplanetary magnetic field is considered. Problems of long-term forecasts of important solar events on the basis of recurrences in the large-scale magnetic field and activity patterns are shown.