On stability of rotation of the mean magnetic field of the Sun

Abstract

New data on the mean magnetic field of the Sun (MMFS) as a star measured at the Crimean Astrophysical Observatory in 1998-2001 are presented. The 34-year time series of the MMFS using similar data from three other observatories (1968-2001, with the total number of daily MMFS values N = 12 428), is considered. It is found that (a) the primary synodic period of the equatorial rotation of solar magnetic field, P⊙ = 26.929 ± 0.015 days, did not vary over the last 34 years, but (b) the average intensity H0 of the photospheric large-scale fields, by modulus, decreased by about 4.5% (with a confidence level of about 80%). The conclusion is made that the longer, 90-year, cycle might be responsible for this potential gradual decrease of H0. The average curve of MMFS variation as plotted with the primary rotational period P⊙ demonstrates an obvious N-S asymmetric of polarities, perhaps associated with the quadrupole and "magnetic disequilibrium" of the Sun as a whole.