Noise and Chaos in a Fractal Basin Boundary Regime of a Josephson Junction

By digital simulations and experiment, we study a Josephson system in a highly nonlinear regime. High experimental noise values appear to correspond in simulations to intrinsic chaotic motion in some regions and to noise-induced hopping between periodic solutions in others. Focusing on the latter, we find correlation between high noise sensitivity and the fractal dimension of the boundary between the basins of the periodic attractors. We show that if enough noise is present to push the orbits into the basin boundary, behavior similar to intrinsic chaos results.