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Two-fluid, three-dimensional, flux-driven, global, electromagnetic turbulencesimulations carried out by using the GBS code are used to identify the mainparameters controlling turbulent transport in the tokamak boundary and todelineate an electromagnetic phase space of edge turbulence. Four turbulenttransport regimes are identified: (i) a regime of fully developed turbulenceappearing at intermediate values of collisionality and $\beta$, with turbulencedriven by resistive ballooning modes, related to the L-mode operation oftokamaks, (ii) a regime of reduced turbulent transport at low collisionalityand large heat source, with turbulence driven by drift-waves, related to ahigh-density H-mode regime, (iii) a regime of extremely large turbulenttransport at high collisionality, which is associated with the crossing of thedensity limit, and (iv) a regime above the ideal ballooning limit at high$\beta$, with global modes affecting the dynamics of the entire confinedregion, which can be associated with the crossing of the $\beta$ limit. Thetransition from the reduced to the developed turbulent transport regime isassociated here with the H-mode density limit and an analytical scaling law formaximum edge density achievable in H-mode is obtained. Analogously, analyticalscaling laws for the crossing of the L-mode density and $\beta$ limits areprovided and compared to the results of GBS simulations.

Turbulent transport regimes in the tokamak boundary and operational limits