Abstract:
A Fourier analysis of sunspot activity during the 1933-1954 period using data entending over the first 10 degrees and all azimuthal orders of the spherical harmonics is presented, and results suggest that the sunspot activity may originate in global solar oscillations with periods of years and decades. However, the finding that the sunspot cycle originates in global modes of about 11-yr periodicity indicates that the set of axisymmetric modes responsible for sunspot activity is different from one sunspot to another. These results contradict the conclusion of Stenflo and Vogel (1986) that axisymmetric modes of only odd parity exhibit 22-yr periodicity in the evolution of the large scale photospheric field.
