Three-Field Model for Drift Waves in a Simple Magnetized Torus

Abstract

A three-field model for resistive drift waves in a weakly ionized plasma, comprising the evolution of particle density, vorticity, and electron temperature, is investigated in a simple toroidal geometry. A derivation of the model is presented, along with a linear normal mode analysis. The non-linear evolution and saturation are studied by means of two-dimensional computations for a double-periodic domain. The analysis is focused in particular on the dependence of the behavior of the system on the parameter C which is inversely proportional to the electron-neutral collision frequency and which couples potential, density and electron temperature fluctuations along the magnetic field. In the adiabatic regime, corresponding to C >> 1 it is found that many of the linear fluctuation characteristics are preserved, including cross phases and a clear wave-like feature with propagation in the electron diamagnetic drift direction. Electron temperature fluctuations in this regime turn out to be strongly damped due to the large parallel heat flux. In the hydrodynamic regime (C << 1) the wave motion is less evident and non-linear behavior prevails. The convective heat transport is seen to dominate the conductive one for all values of the coupling parameter.