  Employing a simple ideal magnetohydrodynamic model in spherical geometry,we
show that the presence of either rotation or finite magnetic helicity is
sufficient to induce dynamical reversals of the magnetic dipole moment. The
statistical character of the model is similar to that of terrestrial magnetic
field reversals, with the similarity being stronger when rotation is
present.The connection between long time correlations, $1/f$ noise, and
statistics of reversals is supported, consistent with earlier suggestions.
