Crisis-induced intermittency due to attractor-widening in a buoyancy-driven solar dynamo

Abstract

In a recent paper [M. A. J. H. Ossendrijver, A&A {\bf 359}, 364 (2000)] numerical simulations of a 2D mean--field model where shown to produce grand minima, typical of the long-term behavior of solar magnetic activity. The model consisted of dynamo that features an $α$ effect based on the buoyancy instability of magnetic fluxtubes, which gives rise to the switching back and forth from grand minima to ``regular&#39;&#39; solar behavior. In this Letter, we report evidence from a time-series analysis of the model for the presence of crisis--induced intermittency due to attractor--widening. We support this finding by showing that the average duration of the minima, $<τ>$, follows the theoretically predicted scaling $<τ> \sim (C_{δα}-C_{δα}^*)^{-γ}$, where $C_{δα}$ is the bifurcation parameter of interest, together with other statistical evidence. As far as we are aware, this is the first time concrete and detailed evidence has been produced for the occurrence of this type of crisis--induced intermittency -- due to attractor widening -- for such dynamo models.