ATTRACTION AND REPULSION OF SPIRAL WAVES BY LOCALIZED INHOMOGENEITIESIN EXCITABLE MEDIA

The anchoring and repelling of spiral waves in a two-dimensional homog eneous excitable medium in the presence of a localized defect is studi ed in the framework of a numerical model and the kinematical theory. D epending on the relative initial distance between the obstacle and the core center, the vortex is observed either to drift towards the obsta cle or to move away from it. The anchoring phenomenon is explained in terms of periodic perturbations of the front curvature, while the repu lsion is rather connected with inhomogeneous refractoriness, which aff ects the spiral tip motion.