An invariant measure is introduced to quantify the disorder in extended locally striped patterns. The measure is invariant under Euclidean motions of the pattern, and vanishes for a uniform array of stripes. Irregularities such as point defects and domain walls make nonzero contributions to the measure. Analysis of patterns generated in a reaction-diffusion system suggests two additional properties of the measure: (1) Apart from small fluctuations, it is invariant for distinct patterns generated at fixed control parameters. (2) It exhibits a jump at the onset of pattern dynamics.

• Received 3 May 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.3281