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We study dynamics of spiral waves in excitable media under spatio-temporal forcing in the form of a traveling-wave modulation of a control parameter. Within a certain range of the modulation frequency a synchronized drift of a spiral wave along a straight line is obtained. A complicated cycloidal-like motion occurs outside this synchronization band. Although circulation of the spiral wave tip is in-phase with external modulation, its rotation frequency is not locked by the applied perturbation. These numerical results obtained for the Oreganator model are confirmed and complemented by analysis of a simplified kinematical model. It is shown that the observed paradoxical phase synchronization is caused by Doppler shift of the modulation frequency in a coordinate system comoving with the spiral wave core.

The evolution of an excitation front propagating on a nonuniformly curved surface is considered within the framework of a kinematical model of its motion. For the case of a surface with a periodically modulated curvature an exact solution of the front shape is obtained under the assumption of sufficiently small surface deformation. The results of the theoretical consideration are compared with the experimental data obtained with a modified Belousov-Zhabotinsky reaction in a thin nonuniformly curved layer.

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