Observations of the solar butterfly diagram from sunspot records suggest
persistent fluctuation in parity, away from the overall, approximately dipolar
structure. We use a simple mean-field dynamo model with a solar-like rotation
law, and perturb the $\alpha$-effect. We find that the parity of the magnetic
field with respect to the rotational equator can demonstrate what we describe
as resonant behaviour, while the magnetic energy behaves in a more or less
expected way. We discuss possible applications of the phenomena in the context
of various deviations of the solar magnetic field from dipolar symmetry, as
reported from analysis of archival sunspot data. We deduce that our model
produces fluctuations in field parity, and hence in the butterfly diagram, that
are consistent with observed fluctaions in solar behaviour