Spontaneous Formation of Multiarmed Spiral Waves in Various Simple Models of Weakly Excitable Media

We investigate a spontaneous formation of stable multiarmed spirals in two-dimensional excitable media, an effect observed in various biological and chemical systems. A previous study based on FitzHugh–Nagumo-type Pushchino model reported a robust effect of stable two- and three-armed spiral formation from nearby vortices, when the spirals rotate around unexcited cores, i.e. when excitability of the medium is low. In this study, we used a powerful parallel computer cluster to perform an extensive parameter search in two other widely used FitzHugh–Nagumo-type models, as well as in the two-component Oregonator model. We observed formation of stable n-armed spirals, with 2 ≤ n ≤ 10, whenever the excitability of the medium was sufficiently low. Thus, we conclude that the formation and persistence of stable multiarmed spirals (MAS) is not an artifact of one particular model, but, rather, it is an amazing higher-level self-organization property of a generic weakly excitable medium. We also establish quantitatively that such multiarmed spirals serve as high-frequency wave sources — a finding that has a direct relevance to cardiac defibrillation research.