Super-modulation of the Sun’s magnetic activity: the effects of symmetry changes

In this paper we argue that the solar activity record, as revealed by telescopic observations and proxy data from the abundances of cosmogenic isotopes, is consistent with the action of a deterministic nonlinear chaotic dynamo. In particular we claim that the long timescale ‘super-modulation’ apparent in the isotopic record can be ascribed to switching of the dynamo between two different modulational patterns. The first (which is currently in operation) involves deep grand minima and occasional changes in symmetry triggered by these minima. The second, which exhibits only weak modulation and no grand minima, arises as a consequence of symmetry breaking. These processes are demonstrated for highly idealized simple models of the nonlinear dynamo equations.