  The variable magnetic field of the solar photosphere exhibits periodic
reversals as a result of dynamo activity occurring within the solar interior.
We decompose the surface field as observed by both the Wilcox Solar Observatory
and the Michelson Doppler Imager into its harmonic constituents, and present
the time evolution of the mode coefficients for the past three sunspot cycles.
The interplay between the various modes is then interpreted from the
perspective of general dynamo theory, where the coupling between the primary
and secondary families of modes is found to correlate with large-scale polarity
reversals for many examples of cyclic dynamos. Mean-field dynamos based on the
solar parameter regime are then used to explore how such couplings may result
in the various long-term trends in the surface magnetic field observed to occur
in the solar case.
