On the Effect of Electron Temperature Fluctuations on Turbulent Heat Transport in the Edge Plasma of Tokamaks: On the Effect of Electron Temperature Fluctuations on Turbulent Heat Transport in the Edge Plasma of Tokamaks

In this paper we study the impact of electron temperature fluctuations in a two-dimensional turbulent model. This modification adds a second linear instability, known as sheath-driven conducting-wall instability, with respect to the previous isothermal model only driven by the interchange instability. Non-linear simulations, backed up by the linear analysis, show that the additional mechanism can change drastically the dynamics of turbulence (scales, density-potential correlation, and statistical momentum). Moreover, its importance relatively to the interchange instability should be more significant in the private flux region than in the main scrape of layer. Its effect on heat transport is also investigated for different regimes of parameters, results show that both instabilities are at play in the heat transport. Finally, the sheath neagtive resistance instability could be responsible for the existence of corrugated heat flux profiles in the scrape-off layer leading to a multiple decay length. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)