On the impact of electric field fluctuations on microtearing turbulence

The magnetic drift and the electric potential play an important role in microtearing destabilization by increasing the growth rate of this instability in the presence of collisions, while in electrostatic plasma micro-turbulence, zonal electric potentials can have a strong impact on turbulent saturation. A reduced model has been developed, showing that the Rechester-Rosenbluth model is a good model for the prediction of electron heat diffusivity by microtearing turbulence. Here, nonlinear gyrokinetic flux-tube simulations are performed in order to compute the characteristics of microtearing turbulence and the associated heat fluxes in tokamak plasmas and to assess how zonal flows and zonal fields affect saturation. This is consistent with a change in saturation mechanism from temperature corrugations to zonal field- and zonal flow-based energy transfer. It is found that removing the electrostatic potential causes a flux increase, while linearly stabilization is observed.

Automated summary

The magnetic drift and theelectric potential affect the growth rate of microtearing instability andturbulent saturation. The Rechester-Rosenbluth model predicts electron heatdiffusivity by microtearing turbulence accurately. Nonlinear gyrokineticflux-tube simulations show that zonal flows and fields influence thesaturation mechanism and heat fluxes in tokamak plasmas.