Anomalous pinch effect and energy exchange in tokamaks

It is shown that, under very generic assumptions of the nature of plasma turbulence in an inhomogeneous magnetic field, the anomalous particle and energy fluxes, in addition to usual diffusive terms, involve purely convective terms not directly associated with density or temperature gradients. The anomalous convective transport results from the conservation, on turbulent time scale, of adiabatic invariants of particle motion in the inhomogeneous magnetic field and the Liouville-theorem constraint on the microscopic dynamics, thus furnishing the mechanism of the anomalous pinch effect in tokamaks. This theory also predicts an electron-turbulence energy exchange, which can be interpreted as a turbulent enhancement of the electron-ion energy exchange. Collisions introduce important modifications to the turbulent mechanisms of the pinch effect. It is argued that the nondiffusive effects are intrinsic to tokamak transport and should be included in power-balance analyses. (C) 1996 American Institute of Physics.