Instabilities Associated with Fast Particles in Toroidal Confinement Systems

Book chapter, 2012

As mentioned in Sect. 6.93, toroidal drift wave transport gives an unfavourable scaling of the energy confinement time with heating power, roughly in agreement with the empirical scaling law (1.8). It is worth observing that this scaling is obtained with a reactive fluid model where only magnetic drift resonances of a fluid type were included. The unfavourable scaling with heating power is due partly to the scaling of transport coefficients with temperature as T−3/2 and partly to the threshold behaviour, i.e. (ηi−ηith)1/2. These are effects of a pure (ideal) heating on the bulk plasma transport and are thus independent of the heating method. We note the close analogy with Rayleigh Benard convection in usual fluids where the heating itself leads to convective transport.