Measurements of kinematical parameters of spiral waves in media of low excitability

The dynamics of spiral waves rotating in a thin layer of the light sensitiv e Belousov-Zhabotinsky reaction mixture are studied under a homogeneous and steady illumination. At a given composition of the excitable medium, the s piral waves meand, when no or low intensity light is applied, or rigidly ro tate, when the light intensity is increased sufficiently. There exists, how ever, a critical value of light intensity above which no wave activity is s upported by the medium, since its excitability is too strongly reduced by t he illumination. In the vicinity of this critical value the basic kinematic al parameters of rigidly rotating spirals (such as the rotation period, wav elength, propagation velocity, and the diameter of the spiral core) are mea sured as a function of the illumination intensity. The experimental observa tions are in good agreement with the predictions based on an earlier propos ed kinematical theory of spiral waves in media of low excitability.