Transition to synchronized chaos via suppression of the natural dynamics

We study the mechanism of synchronization for a periodic Van der Pol oscill ator driven by a strong chaotic forcing from a Rossler system. It is demons trated how thr system with increasing coupling strength adjusts its motion in accordance with the external forcing via the suppression of its natural dynamics by the chaotic signal. This transition is traced both in the power spectrum and in the spectrum of Lyapunov exponents. We identify the underl ying mechanism as a set of inverse Hopf bifurcations of saddle orbits embed ded in the synchronized chaotic set. (C) 2001 Published by Elsevier Science B.V.