Manifestation of Rossby Waves in the Global Magnetic Field of the Sun during Cycles 21–24

Abstract

Abstract The evolution of the solar global magnetic field (GMF) was investigated and compared with oscillations of different periods during cycles 21–24. The data from the Wilcox Solar Observatory were used. The results indicate that GMF structures were associated with certain oscillations. Oscillations of 81.83–163.65 days were associated with structures lasting 10–20 CRs. They occurred as some pulses during solar maxima. Oscillations of 163.652–463.680 days were associated with GMF structures lasting ≈20–50 CRs. They match two peaks in the magnetic-field cycle. Oscillations of 1.270–5.231 yr were formed during the dominance of the sectorial GMF structure. Oscillations of 5.231–13.451 yr were the most intense. From cycle 22 to 24, their intensity decreased, and the range of periods narrowed and shifted to longer periods, determining the corresponding changes in the oscillations of 81.83 days–5.231 yr and associated GMF structures. They match well the evolution of the zonal GMF structure. They are assumed to be a descending part of a period of ≈≥60 yr. A decrease in the magnetic field from cycle 22 to 24 may be due to a decrease in the intensity of these oscillations. Some periodicities of the revealed oscillations are in good agreement with the estimates of the periods for fast magnetic Rossby waves. The GMF structure connection with Rossby waves is discussed.