The Influence of trapped electron mode driven zonal flow on electron temperature gradient driven turbulence

Asahi, Yuichi   ; Ishizawa, Akihiro*; Watanabe, Tomohiko*; Sugama, Hideo*; Tsutsui, Hiroaki*; Iio, Shunji*

Turbulent transport driven by electron temperature gradient (ETG) modes and trapped electron modes (TEMs) is investigated by means of gyrokinetic simulations. It is found that ETG turbulence can be suppressed by zonal flows driven by TEMs. Then, the mechanism of the regulation of ETG turbulence by zonal flows is investigated by nonlinear entropy transfer analysis. Firstly, it is confirmed that the entropy is transferred from TEMs to zonal flow. Secondly, it is found that the zonal flows in the steady state meditate the entropy transfer of the ETG modes from low to high radial wavenumber regions. In short, it is quantitatively shown that the zonal flows is driven by TEMs and the ETG turbulence is regulated by the TEM-driven zonal flows.