IP4 ~ Monday, May 22, 1995 ~ 8:30 AM
Turbulent Vortex Rings in Excitable Media
Certain physiological and chemical media exhibit an "excitability" now well understood in terms of local reaction mechanisms coupled in space by diffusion (of electrical potential or of molecules). Such motionless media support unattenuated propagation of a curved wave front in which the local state makes an excursion from quiescence. In 3D, the wave front can have an internal edge, which becomes a vortex filament, typically closed in a ring. Its reproducible but seemingly irregular spontaneous motions even in uniform isotropic media far from boundaries remain to be even described, still less interpreted, except in special limiting cases. But they have some topological regularities. For example, in numerical experiments several qualitatively distinct configurations seem unable to shrink and vanish like the simplest vortex rings. These stubbornly persistent "organizing centers" seem so robust that they ought to be observable in laboratory experiments, given suitable initial conditions to evoke them.
Arthur T. Winfree
Department of Ecology and Evolutionary Biology, University of Arizona