Breaking of equatorial symmetry in a rotating system: A spiralling intermittency mechanism

Rotating fluid systems can display large-scale asymmetries about the equator. A model-independent mechanism for such symmetry breaking is described, via a spiralling intermittency that combines the on-off and Pomeau-Manneville mechanisms. This involves a periodic orbit in an invariant subspace becoming unstable to perturbations transverse to the subspace; these are describable in terms of the equatorial symmetry of the system. A scaling law is derived for the intermittency and this is tested against results from the numerical simulation of the behaviour of a rotating electrically conducting fluid. Finally we make comparisons with recent results on intermittency and symmetry breaking.