3-DIMENSIONAL COLLISIONAL DRIFT-WAVE TURBULENCE - ROLE OF MAGNETIC SHEAR

Three-dimensional (3-D) nonlinear simulations of collisional drift-wav e turbulence are presented. Results for the Hasegawa-Wakatani equation s (without magnetic shear) in 3-D are compared to former two-dimension al (2-D) simulations. In contrast to the 2-D system the 3-D situation is completely dominated by a nonlinear drive mechanism. The final stat e of the system is sensitive to the configuration of the computational grid since the sheared flow develops at the longest: scales of the sy stem. When magnetic shear is included, the system is linearly stable b ut the turbulence is self-sustained by basically the same nonlinear me chanism. Magnetic shear limits the size of the dominant eddies, so the system evolves to a stationary turbulent state independent of the com putational box. Finally, it is shown that the level of turbulence in t he system with magnetic shear depends sensitively on the size of the e ffective Larmor radius rho(s) compared with the characteristic transve rse scale length of the eddies. (C) 1996 American Institute of Physics .