Forced excitations and excitable chaos in the photosensitive Oregonator under periodic sinusoidal perturbations

The responses of an excitable system to external periodic perturbations are studied by using the photosensitive Oregonator that is a three variable model of the photosensitive Belousov–Zhabotinsky reaction. The system is set at the vicinity of the subcritical Hopf bifurcation point, and sinusoidal perturbation is given by light: ϕ ( α , ν ) = ϕ 0 − α A 0 sin ⁡ ( 2 π ν τ ) . The dynamic threshold for firing appears as a U-shaped line in ν – α plane. Under high-frequency perturbations, the system shows a subthreshold period-doubling cascade, subthreshold chaotic responses (excitable chaos) and reaches firing chaos as a result of expansion of orbits around the fixed point.