The effect of internal noise on the period-2 behavior is investigated
in low-dimensional dynamical systems. To treat the morphological compl
exity of such attractors, a general stochastic formulation using a sui
table moving frame in the Gaussian approximation is set up. Its applic
ability is illustrated on a specific model, the Willamowski-Rossler ch
emical scheme. Using this approach, we are able to interpret the direc
t simulations of the master equation which show significant changes wi
th respect to the deterministic behavior. Specifically, a band merging
in the multi-periodic regime which at first sight seems to disrupt th
e bifurcation cascade is observed. Marked inhomogeneities in the fluct
uations distribution along the period-2 attractor explaining these fea
tures are brought out.