Transition from Simple Rotating Chemical Spirals to Meandering and Traveling Spirals

Experiments on the Belousov-Zhabotinksy reaction unfold the bifurcation from simple (temporally periodic) rotating spirals to meandering (quasiperiodic) spirals in the neighborhood of a codimension-2 point. There are two types of meandering spirals, inward-petal (epicycloid) spirals and outward-petal (hypocycloid) spirals. These two types of meandering regimes are separated in the phase diagram by a line of traveling spirals that terminates at the codimension-2 point. The observations are in good accord with theory.