When the observed pattern of solar magnetic fields is decomposed in its spherical-harmonic components and a time series analysis is performed, a resonant global wave pattern is revealed. The power spectrum indicates modes with discrete frequencies, obeying a strict parity selection rule in the case of the zonal, rotationally-symmetric modes (with spherical-harmonic order m = 0). For instance, the 22 yr resonance that dominates for the anti-symmetric modes (with odd values of the spherical-harmonic degree l) is completely absent for the symmetric modes, which instead exhibit a number of resonances having frequencies increasing with l.