Noise driven avalanche behavior in subexcitable media

The interaction of noise with a subexcitable chemical system gives rise to spatiotemporal behavior with novel statistical properties. Wave behavior in a photosensitive Belousov-Zhabotinsky reaction with imposed noise is monit ored and statistically analyzed. Waves are initiated at sites where the acc umulation of subthreshold perturbations induces local excitations, and wave s propagate through the medium by a facilitated percolation process. Statis tical analysis of the coherent spatiotemporal structures reveals power-law relations that indicate the system has no intrinsic length or time scale.