Attractor bubbling in coupled hyperchaotic oscillators

We investigate experimentally attractor bubbling in a system of two coupled hyperchaotic electronic circuits. The degree of synchronization over a ran ge of coupling strengths for two different coupling schemes is measured to identify bubbling. The circuits display regimes of both attractor bubbling and high-quality synchronization. For the coupling scheme where high-qualit y synchronization is observed, the transition to bubbling is "soft" and its scaling with coupling strength near the transition point does not fit into the known categories of transition types. We also compare the observed beh avior to several proposed criteria for estimating the regime of high-qualit y synchronization. It is found that none of these methods is completely sat isfactory for predicting accurately the regimes of attractor bubbling and h igh-quality synchronization.