SPIRAL WAVE MEANDER IN EXCITABLE MEDIA - THE LARGE-CORE LIMIT

We show that the dynamics of spiral waves in excitable media can be re duced to a nonlinear equation of motion for the wave tip that is asymp totically exact in a parameter range where the motion takes place arou nd a large central core region. The onset of meander is shown to occur naturally in this range in the usual free-boundary limit where the me dium exhibits an abrupt response to a stimulus. This equation provides a simple understanding of the physical origin of the meandering insta bility of spiral waves and of the quasiperiodic motion of the wave tip .