Stochastic multiresonance in a chaotic map with fractal basins of attraction

Noise-free stochastic resonance in a chaotic kicked spin model at the edge of the attractor merging crisis is considered. The output signal reflects the occurrence of crisis-induced jumps between the two parts of the attractor. As the control parameter-the amplitude of the magnetic field pulses-is varied, the signal-to-noise ratio shows plateaus and multiple maxima, thus stochastic multiresonance is observed. It is shown that the multiresonance occurs due to a fractal structure of the precritical attractors and their basins. In the adiabatic approximation theoretical expression for the signal-to-noise ratio is derived, based on the theory of oscillations in average crisis-induced transient lifetimes. Numerical and theoretical results agree quantitatively just above the threshold for crisis and qualitatively in a wide range of the control parameter.