Progress on theoretical issues in modelling turbulent transport

We discuss theoretical progress in turbulent transport modelling in tokamaks. In particular, we address issues that the conventional quasilinear type calculation cannot confront, such as (i) the nature of turbulence in the edge-core coupling region of tokamaks (i.e. the so-called 'no man's land'), and the dynamics of incoming structures coupled to zonal flows, (ii) nonlinear dynamics of zonal flows and (iii) transport by drift wave turbulence with strong wave–particle interaction. A unifying theme of these studies is their formulation in terms of the phase space density correlation evolution. (paper)