Resistivity gradient driven versus drift wave turbulence

Abstract

Drift wave and rippling mode turbulences are investigated numerically in a 2-D slab, using the full fluid electron dynamical system from which both spring. Non-adiabatic electron dynamics capable of free energy access from temperature and density gradients are localized in the vicinity of the resonant surface, either by resistive dissipation/thermal conduction or by 'rippling', i.e. coupling of temperature and electrostatic potential fluctuations by the equilibrium current. Which type of turbulence prevails, self-organized drift wave or instability driven rippling mode, is determined solely by the competition between these two localization mechanisms. Because the localization is through linear terms, the regime boundary between the two types of turbulence is precisely where the linear theory of Hassam and Drake (Phys. Fluids 26 (1983) 133) says it is. And since even the most collisional edge plasmas in tokamaks such as ASDEX or TFTR are firmly ensconced within the drift wave regime, it is concluded that 'resistivity gradient driven turbulence' has no relevance to present or future tokamak experiments. Non-linearly self-sustaining collisional drift wave turbulence, on the other hand, remains viable