INTERCHANGE INSTABILITY TURBULENCE MODEL IN EDGE TOKAMAK PLASMA

Interchange instability is investigated as a plausible mechanism to drive turbulence in the tokamak scrape-off-layer. By averaging density and electrostatic potential fluid equations along field lines, a reduced two dimensional model is obtained. Similarly to Rayleigh-Benard convection, interchange instability shows a instability threshold and presents localised modes (with a simple geometry and boundary conditions). The nonlinear, turbulent, behaviour of the model is investigated using numerical simulations. Preliminary results show a self-organization of the flow in coherent structures with a departure from gaussian statistics.