Diffusion, intermittency, and noise-sustained metastable chaos in the Lorenz equations: Effects of noise on multistability

Multistability is an interesting phenomenon of nonlinear dynamical systems. To gain insights into the effects of noise on multistability, we consider the parameter region of the Lorenz equations that admits two stable fixed point attractors, two unstable periodic solutions, and a metastable chaotic "attractor". Depending on the values of the parameters, we observe and characterize three interesting dynamical behaviors: ( i) noise induces oscillatory motions with a well-defined period, a phenomenon similar to stochastic resonance but without a weak periodic forcing; ( ii) noise annihilates the two stable fixed point solutions, leaving the originally transient metastable chaos the only observable; and ( iii) noise induces hopping between one of the fixed point solutions and the metastable chaos, a three-state intermittency phenomenon.