Low frequency oscillations and chaos in plasmas

Regular and chaotic low frequency oscillations are studied in thermionic discharges. A model for relaxation oscillations is presented that is based on particle‐in‐cell simulations and probe measurements. The synchronization of the oscillations by an external driver and the period‐doubling route to chaos can be understood in terms of a periodically forced van der Pol oscillator. The stabilization of unstable periodic orbits by the Ott‐Grebogy‐Yorke technique is demonstrated. Spatio‐temporal chaos is found at the onset of drift‐wave turbulence. Here the transition to chaos involves the Ruelle‐Takens‐Newhouse scenario with a sequence of Hopf bifurcations. The spatio‐temporal evolution of interacting drift‐waves is studied with a novel 64‐probe array.