Parametric resonance of a vortex in an active medium

Abstract
Experimental observation of parametric resonance of a vortex in an active medium is reported. Unlike the parametric resonance in conservative systems, no parametric pumping of energy is involved here, making the resonance especially interesting. An alternating electric-field with frequency, equal to double frequency of the vortex rotation, has induced the vortex drift in the Belousov-Zhabotinsky chemical active medium. The drift velocity was about 1/5 of the vortex drift velocity in constant electric field with the same amplitude. The direction of the drift did not coincide with the direction of the electric field and could be arbitrarily chosen by changing the phase shift between the electric-field oscillations and the vortex rotation. No effects were observed at a frequency equal to the frequency of vortex rotation, as well as at nonresonant frequencies.