Effect of Edge Shear Flow on Radial Spreading of Ballooning Mode Turbulence

Turbulent transport by the ballooning mode in tokamak plasmas with edge pedestals is simulated using a reduced set of two-fluid equations. In the absence of the equilibrium poloidal flow, global heat transport by the secondary nonlinear evolution of the resistive ballooning mode turbulence is observed. By examining the effect of the edge shear flow, the global heat transport is suppressed to be almost half, if the edge shear flow is strong enough. A detailed analysis on the radial profile and the poloidal spectrum of the heat flux is newly performed. It is revealed that such confinement improvement is caused by the suppression of the formation of streamer structures that lead to the strong convective heat transport.