Intermittency transitions to strange nonchaotic attractors in a quasiperiodically driven Duffing oscillator

Different mechanisms for the creation of strange nonchaotic attractors (SNA s) are studied in a two-frequency parametrically driven Duffing oscillator. We focus on intermittency transitions in particular, and show that SNAs in this system are created through quasiperiodic saddle-node bifurcations (ty pe-I intermittency) as well as through a quasiperiodic subharmonic bifurcat ion (type-m intermittency). The intermittent attractors are characterized v ia a number of Lyapunov measures including the behavior of the largest nont rivial Lyapunov exponent and its variance, as well as through distributions of finite-time Lyapunov exponents. These attractors an ubiquitous in quasi periodically driven systems; the regions of occurrence of various SNAs are identified in a phase diagram of the Duffing system.