EFDA-JET-CP(04)03/25
On the Momentum Re-Distribution via Fluctuations in Fusion Plasmas
The mechanisms underlying the generation of plasma flows play a crucial role in understanding transport in magnetically confined plasmas. The amplitude of parallel flows in the Scrape-Off Layer (SOL) is significantly larger than those resulting from simulations. Recent experiments have pointed out the possible influence of turbulence to explain flows in the plasma boundary region. In this context, it has been suggested that poloidal gradients induced by ballooning like turbulent fluxes in the outer SOL region are drivers for parallel flows and coupling between turbulent transport and parallel flows have been reported. In order to quantify the link between flows and turbulence, the energy transfer between them is under investigation. However, in view of recent results, some caution should be taken in the interpretation of probe results since it may locally perturb the plasma. In the plasma core region evidence of anomalous toroidal momentum transport has been reported in different devices and different mechanisms have been proposed to explain those results including neoclassical effects, turbulence driven models and, in the case of ICRF heating, fast particle effects. Spontaneous toroidal flow not driven by neutral beams has also been observed in stellarator devices. This paper reports recent experimental results dealing with the link between parallel flows and fluctuations in the plasma boundary region of tokamaks (JET) and stellarators (TJ-II).