LARGE-SCALE MAGNETIC-FIELD STRUCTURES AND CORONAL HOLES ON THE SUN

This paper is aimed at establishing the relationship between the large -scale magnetic fields (LSMF), coronal holes (CH), and active regions (AR) in the Sun. The LSMF structure was analyzed by calculating the ve ctor photospheric magnetic field under a potential approximation. Syno ptic maps were drawn to study the distribution of the B perpendicular to field component and to isolate regions where the open field lines o f the unipolar magnetic field are most radial. These are the sites of occurrence of X-ray and He I 10 830 Angstrom coronal holes detected fr om the SXT/Yohkoh images. It is shown that coronal holes are usually l ocated in LSMF regions with a typical pattern of divergent B perpendic ular to vectors and a so-called 'saddle' configuration. B perpendicula r to vectors from the 'conjugate' (spaced by 90 degrees) coronal holes converge towards the active regions between CH. Variations in AR dist ort coronal holes and change their boundaries. This implies that the e nergy regime in CH depends on the energy supply from the active region . The LSMF structure is more stable than coronal holes: remaining prac tically unchanged during tens of rotations of the Sun. Thus, a peculia r-magnetically coupled system of LSMF/CH/AR has been revealed. A model has been suggested to describe the interaction of the emerging toroid s in the convection zone and in the photosphere. The cellular convecti on, that develops at the center of the toroids, is responsible for the occurrence of active regions. The model qualitatively describes the o bserved particularities of the LSMF/CH/AR system.