ENTRAINMENT AND RESONANCE OF SPIRAL WAVES IN ACTIVE MEDIA WITH PERIODICALLY MODULATED EXCITABILITY

We study frequency locking and resonance of spiral waves in an active medium subjected to periodic forcing with adjustable frequency. The ex periments are carried out with a modified Belousov-Zhabotinsky system whose excitability is light-sensitive. In the meander regime of compou nd rotation we find entrainment bands if the sum of the two basic freq uencies determining the dynamics of the spiral tip is a rational multi ple of the modulation frequency. We observe resonance if the ratio bet ween the forcing period and the mean excitation period outside of the pattern is equal to one, two, etc. The experimental results are in qua litative agreement with data of numerical simulations obtained using a two-variable Oregonator scheme. This model takes account of an additi onal flow of the inhibitor bromide produced photochemically.