Radially Locked Sun-Ray Patterns in Reaction-Diffusion-Advection Systems

Traveling fronts ubiquitous in physics, chemistry, and biology are prone to transverse cellular deformations due to diffusive or convective instabilities. Here, we show both theoretically and experimentally that new patterns can be obtained if the destabilization is triggered around a front locked radially by advection. Specifically, angularly shifting sun-ray-like patterns can develop around an autocatalytic front frozen by radial advection. These patterns arise from a diffusive instability that occurs when the autocatalyst X and the reactant Y diffuse at different rates. The properties of these shining-star structures can be controlled by tuning the flow rate Q and the ratio of diffusion coefficients δ as evidenced by linear stability analysis, nonlinear simulations, and experiments on the chlorite-tetrathionate reaction.