Merging of resonance tongues

Abstract This paper considers the resonance behavior found near a saddle-node/Hopf bifurcation in a flow. The global structure of resonance tongues is examined, and it is shown that, in the absence of certain symmetries, different resonance tongues can merge with one another. The position and shape of the resonance tongues are seen to be related to the presence of homoclinic and heteroclinic bifurcations of two saddle-foci. The implications of these results for the normal form analysis of the saddle-node/Hopf bifurcation are discussed.