SHEAR-FLOW EFFECTS ON THE NONLINEAR EVOLUTION OF THERMAL INSTABILITIES

In the weak radiation drive regime, the coupling between the thermal i nstability driven by impurity radiation and the self-consistent flow p rofile modification leads to a simple dynamical system that can be app roximated by the Volterra-Lotka equations. In this system the shear fl ow acts as a predator and the temperature fluctuations act as prey. Th e solutions are oscillatory, and their behavior resembles that of edge -localized modes (ELM's). The solutions of the simplified model are co mpared with the three-dimensional and two-dimensional nonlinear numeri cal results for this instability.