Resistive drift wave and interchange turbulence in a cylindrical plasma with magnetic and velocity shear

Abstract

By solving numerically the two-field nonlinear model equations for the potential and density fluctuations in the presence of a density gradient, magnetic curvature with shear, and poloidal velocity shear, turbulent spectra and diffusion rates are studied. When the adiabatic parameter (Ωe/νe)(ρs2/R2)/(κρs) is small, a trend of a dual cascade, normal cascade of the density fluctuations, and an inverse cascade of the potential fluctuations, is seen in the wave number spectra, producing a large particle flux proportional to νe1/3. Here R is the major radius, ρs is the ion Larmor radius at the electron temperature, Ωe is the electron cyclotron frequency, νe is the electron ion collision frequency, and κ is an inverse scale length of the background density gradient. Parallel wave numbers are represented by 1/R. For large (Ωe/νe)(ρs2/R2)/(κρs), the electrons become adiabatic, with a significantly reduced particle flux proportional to νe. In the presence of an externally imposed radial electric field with a negative (positive) polarity, Er<0 (Er≳0), the poloidal velocity shear in the E×B drift motion suppresses (enhances) the fluctuation level in the growth phase; however, these effects practically disappear in the saturated state. The radial electric field produced by the inverse cascade due to the convective nonlinearity is also studied; however, its effect on the particle transport is mild.