Nonlinear Instability Mechanism in 3D Collisional Drift-Wave Turbulence

Numerical simulations of 3D collisional drift-wave turbulence reveal a behavior basically different from that found in previous 2D studies. The linear instability saturates due to energy transfer to small $k_z$ leading to the formation of convective cells. The turbulence is sustained by nonlinear transfer processes between $k_z=0\mathrm{}$ and $k_z\ne 0$ modes, the latter acting as a catalyst. The system tends to relax to a nonturbulent poloidal shear flow.