Session 6F - Magnetic Confinement.
ORAL session, Wednesday afternoon, November 13
Vail Room, Adam's Mark
Nonlinear dynamics of the interchange (or ballooning mode) turbulence is studied theoretically by taking into account the electron inertia effect. Method of dressed-test mode is developed, and Lagrange nonlinearity is renormalized in a form of turbulent transport coefficient. The effective mass of electrons becomes heavier due to fluctuations, causing the nonlinear growth above the threshold level. The amplitude of the stationary fluctuations is expressed in terms of the pressure gradient. It is shown that the backward bifurcation appears near the linear stability boundary. The subcritical nature of the turbulence is explicitly shown. The critical pressure gradient for the transition from collisional transport to the turbulent transport is obtained. The self-sustained turbulent state is found to maximize the entropy production rate. The result provides a prototype for the system far from the thermal equilibrium. The pressure gradient plays a role of the order parameter in the nonlinear-nonequilibrium system and characterizes the turbulence (the level, scale length, decorrelation rate, etc.). Extending the analysis to the electromagnetic turbulence, the turbulence-turbulence transition is also found. The dynamical equations for the turbulence are provided and applied to the transition physics like L-H transition or ELMs. As well as the analytical insight of the problem, the nonlinear simulation of the turbulence is also reported.