Force exerted on the spiral tip by the heterogeneity in an excitable medium

Heterogeneity exerts a repulsive force on the approaching spiral tip, and the attractive force prevents the spiral tip from unpinning from the heterogeneity once the tip has anchored. Studying the two kinds of forces in the same context enables comparisons between them. Findings indicate the following: 1) the value of the attractive force is about a few tells that of the repulsive force for different parameter values; 2) the repulsive and attractive forces always increase with the level of heterogeneity; and 3) compared with the size of the heterogeneous area the level of heterogeneity influences the forces more significantly. Copyright (C) EPLA, 2013