Structure and cyclic evolution of large-scale solar magnetic fields

The global magnetic field of the Sun is regarded as consisting of 4 main field systems: 1) the axial dipole field, which is most pronounced at polar latitudes (phi > similar to 50 degrees); 2) the inclined dipole field in the equatorial region (phi < similar to 50 degrees); 3) the quadrupole component (a system of super giant cells with a size of similar to 80 degrees -110 degrees) that manifest itself in the form of a 4-sector field structure; and 4) the multipole component of orders higher than quadrupole. The global field and each of its components are quantitatively characterized by the total and partial magnetic field indices. The absolute and relative contribution of each field component in different phases of the solar cycle are displayed for solar cycles 20, 21 and 22. The physical meaning of solar cycle reference points is discussed.