Feedback-controlled forcing of meandering spiral waves in an open gel reactor

The control of spiral wave dynamics has attracted much interest recently. Besides external forcing at a fixed frequency, feedback-controlled forcing has been studied. One of the simplest feedback schemes is to measure the activity level at a particular point of the medium continuously and to apply a spatially uniform pulsatory modulation if a certain threshold is reached at the detector. We have realized this feedback loop using an open gel reactor for the light-sensitive Belousov-Zhabotinskii medium. This allows us to maintain stationary non-equilibrium conditions over several hundred rotation periods of the unperturbed spiral wave. By varying the distance between the detector and the spiral tip, we find different stable branches of the resonance attractor for the same medium. We confirm the constant spacing between neighboring stable branches as predicted by Zykov and Karma and measure the dependence of the resonance drift on the forcing amplitude.