Multiple reversals of pulse waves in an excitable medium resulting from switching the polarity of dc electric fields

A planar wave propagating in the Belousov–Zhabotinsky reaction medium with pyrogallol as substrate is shown to undergo multiple reversals upon switching the polarity of an imposed dc electric field. During the multiple reversals an asymmetry arises in: (i) the propagation velocities of reversed waves, (ii) the ferroin concentrations in front of reversed waves shortly before switching the electric field polarity, and (iii) the location at which a new wave emerges in the wake of the original one. Multiple reversals occur in a limited range of control parameter values and depend on the pyrogallol concentration.