THE PINCH EFFECT EXPLAINS TURBULENT TRANSPORT IN TOKAMAKS

The pinch effect of the particles, which is observed in all tokamaks, furnishes the key to the selection of dominant turbulence modes. The c oncept of a turbulent uniform distribution of particles over some phas e-space surfaces specified by the geometry of the magnetic field and b y invariants is introduced. Large-scale electrostatic modes lead to a turbulent uniform distribution nq = const with a maximum particle dens ity at the center of the column. They also lead to a natural explanati on of the self-consistency of profiles. These modes can be transformed to the greatest extent by radial electrostatic fields, in accordance with the phenomenology of L-H-VH transitions. (C) 1994 American Instit ute of Physics.