Modelling of the edge plasma with account of self-consistent electric fields

Recent results on the simulation of the edge plasma parameters are discussed with emphasis on the role of self-consistent electric fields. It is demonstrated that simulation with B2SOLPS5.0 code as well as with the other codes is consistent with the neoclassical nature of the radial electric field in the core region 1-2 cm inside the separatrix. Near the separatrix the viscous layer exists, where the impact of the parallel fluxes of the SOL is important and electric field deviates from the neoclassical value. It is shown that the experimental dependence of the L-H transition threshold on the local and global plasma parameters might be explained on the basis of the simulations. The impact of the geometrical factors on the radial electric field structure is discussed. It is shown that the change of the parallel fluxes in the scrape-off layer, which are transported through the separatrix due to turbulent viscosity and diffusivity, should result in variation of the radial electric field. The parallel (toroidal) fluxes in the SOL and mechanisms of their formation are analyzed for different geometry and directions of the magnetic field. Currents in the SOL and in the core region are analyzed and compared with the analytical predictions. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.