Ion radial transport in the Tara central cell

Abstract

The radial transport rate of bulk ions in the Tara central cell, in a globally axisymmetric configuration, is determined by comparing the ionization source profile deduced from axial two-dimensional measurements of Hα emission with the axial electron end-loss profile. The radial transport of an impurity ion is also calculated, from the departure of the radial profile of O V from coronal equilibrium. The two techniques yield comparable transport coefficients: D ∼ 3 × 104cm2 · s−1 and v ∼ – 1000r cm · s−1, near the plasma core. A separate technique is used to deduce a lower bound for the edge bulk ion radial transport rate of 3 × 105 cm2 · s−1. Azimuthal electric fields are proposed as the likely source of particle transport.