Magnetic field reversals and long-time memory in conducting flows
  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. 
P. Dmitruk, P.D. Mininni, A. Pouquet, S. Servidio and W.H. Matthaeus
physics.flu-dyn astro-ph.EP physics.geo-ph physics.plasm-ph