EXPERIMENTAL SURVEY OF SPIRAL DYNAMICS IN THE BELOUSOV-ZHABOTINSKY REACTION

We present a systematic study of spiral waves in the Belousov-Zhabotin sky reaction in a spatial open reactor, where the concentrations of su lfuric acid, sodium bromate, and malonic acid are varied. Within this parameter space, three kinds of instabilities arise: two of them, whic h we identify as the retracting wavefront and convective instabilities , lead to the destruction of the spiral pattern, and mark the boundari es of the spiral existence domain in parameter space. Inside this doma in, there exists a region where simply rotating spirals undergo the me andering instability. Quantitative measurements of the asymptotic char acteristics of simple spirals provide scaling relations between the ob servables: the pitch varies as the square root of the period. They bot h diverge with simple exponents at the retracting wavefront instabilit y. This organization, reminiscent of a second order phase transition, allows us to consider the spiral a critical pattern. Comparison with s everal models and numerical simulations indicates the validity or disc repancies of applying these theoretical approaches to our experimental results.