PHASE-SPACE OF TOKAMAK EDGE TURBULENCE, THE L-H TRANSITION, AND THE FORMATION OF THE EDGE PEDESTAL

Based on three-dimensional simulations of the Braginskii equations, we identify two main parameters which control transport in the edge of t okamaks: the MHD ballooning parameter and a diamagnetic parameter. The space defined by these parameters delineates regions where typical L- mode levels of transport arise, where the transport is catastrophicall y large (density limit) and where the plasma spontaneously forms a tra nsport barrier (H mode).