Experimental survey of spiral dynamics in the belousov-zhabotinsky reaction

We present a systematic study of spiral waves in the Belousov-Zhabotinsky reaction in a spatial open reactor, where the concentrations of sulfuric acid, sodium bromate, and malonic acid are varied. Within this parameter space, three kinds of instabilities arise: two of them, which we identify as the retracting wavefront and convective instabilities, lead to the destruction of the spiral pattern, and mark the boundaries of the spiral existence domain in parameter space. Inside this domain, there exists a region where simply rotating spirals undergo the meandering instability. Quantitative measurements of the asymptotic characteristics of simple spirals provide scaling relations between the observables: the pitch varies as the square root of the period. They both diverge with simple exponents at the retracting wavefront instability. This organization, reminiscent of a second order phase transition, allows us to consider the spiral a critical pattern. Comparison with several models and numerical simulations indicates the validity or discrepancies of applying these theoretical approaches to our experimental results.