The extended solar cycle and asymmetry of the large-scale magnetic field

Abstract

ABSTRACT Traditionally, the solar activity cycle is thought as an interplay of the main dipole component of the solar poloidal magnetic field and the toroidal magnetic field. However, the real picture as presented in the extended solar-cycle models is much more complicated. Here, we develop the concept of the extended solar cycle clarifying what zonal harmonics are responsible for the equatorward and polarward propagating features in the surface activity tracers. We arrive at a conclusion that the zonal harmonics with l = 5 play a crucial role in separating the phenomena of both types, which are associated with the odd zonal harmonics. Another objective of our analysis is the role of even zonal harmonics, which prove to be rather associated with the north–south asymmetry of the solar activity than with its 11-yr solar periodicity.