Interchange turbulence and radial transport in tokamak scrape-Off layer dominated by meso scale structure

A nonlinear simulation of scrape-off layer (SOL) interchange turbulence is performed using a two dimensional Hasegawa-Wakatani-type model. In the initial stage of nonlinear evolution, blobs are observed to form and detach from the separatrix. The blobs propagate radially and deform owing to the Kelvin-Helmholtz instability. During the nonlinear stage, an inverse cascade occurs and radially elongated meso scale structures are created. These structures are broken into pieces by the boundary effect when they touch the wall. Finally, the system reaches a quasi-steady state and intermittent transport appears. The velocity of the convective transport is estimated from the slope of the auto correlation function in the quasi-stady state, and it agrees with the velocity estimated using a model for a single blob whose size corresponds to that of a typical meso scale structure. This result indicates that meso scale structures play an important role in convective transport in the SOL.