Figure 9.

Two possible effects of additive noisy fluctuations in a slow–fast system. (a) If the slow–fast system is in the excitable regime, then noisy fluctuations can cause excitations. Excitations will be sporadic if the amplitude of the oscillations is weak (as shown here), or regular, as in a limit cycle, in the coherent resonance regime. (b) If the slow–fast system is oscillating, then additive fluctuations may cause early or delayed escapes from the slow branches, compared with the deterministic system. The net effect is a shortening of the cycle duration. (Online version in colour.)