NONNORMAL PARAMETER BLOWOUT BIFURCATION - AN EXAMPLE IN A TRUNCATED MEAN-FIELD DYNAMO MODEL

We examine global dynamics and bifurcations occurring in a truncated m odel of a stellar mean-field dy name. This model has symmetry-forced i nvariant subspaces for the dynamics and we find examples of transient type I intermittency and blowout bifurcations to transient on-off inte rmittency, involving laminar phases in the invariant submanifold. In p articular, our model provides examples of blowout bifurcations that oc cur on varying a non-normal parameter that is, the parameter varies th e dynamics within the invariant subspace at the same time as the dynam ics normal to it. As a consequence of this we find that the Lyapunov e xponents do not vary smoothly and the blowout bifurcation occurs over a range of parameter values rather than a point in the parameter space .