Gradient induced spiral drift in heterogeneous excitable media.

Nonlinear excitable systems far from equilibrium can exhibit pattern formation such as spirals, target patterns, etc. One such system is the heterogeneous catalytic reaction of CO with oxygen on platinum single crystals. It has been established that the resonant periodic forcing of spirals in such excitable systems can cause a spiral drift. Here, we investigate the effects of a linear thermal gradient on the spiral dynamics during CO oxidation on platinum (110) for the first time, both in simulations and with experiments. Our results suggest that a spatial thermal gradient established across the surface can act as an internal forcing drive and cause the spiral patterns to drift. This drift has components both parallel and perpendicular to the external gradient.