Inwardly rotating spirals in nonuniform excitable media

(Received 19 August 2011; revised manuscript received 28 November 2011; published 24 January 2012)Inwardlyrotatingspirals(IRSs)haveattractedgreatattentionsincetheirobservationinanoscillatoryreaction-diffusion system. However, IRSs have not yet been reported in planar excitable media. In the present work weinvestigate rotating waves in a nonuniform excitable medium, consisting of an inner disk part surrounded byan outer ring part with different excitabilities, by numerical simulations of a simple FitzHugh-Nagumo model.Depending on the excitability of the medium as well as the inhomogeneity, we find the occurrence of IRSs, ofwhich the excitation propagates inwardly to the geometrical spiral tip.DOI: 10.1103/PhysRevE.85.016213 PACS number(s): 89