The poloidal variation of the radial transport due to electrostatic fluctuations in toroidal magnetic confinement experiments

Abstract

The `anomalous' radial transport in the plasma edge is generally thought to be largely due to correlated fluctuations of plasma density, temperature and potential. Experimental results show that fluctuations of these quantities are highly correlated, in phase and of constant amplitude parallel to the magnetic field. The resulting transport is often described by diffusive terms, using anomalous transport coefficients. The objective of this paper is to show that, in keeping with the high correlation and constant amplitude of the fluctuations along the magnetic field, the transport coefficients should scale as the square of the flux expansion (i.e. the separation between magnetic flux surfaces) along a magnetic flux tube in order to describe the fluctuation-induced transport correctly.