Nonlinear excitation of zonal flows by turbulent energy flux

The nonlinear excitation of zonal flows (ZFs) generated by the ion-temperature-gradient turbulence in a tokamak plasma is investigated by using the global gyrokinetic code NLT. It is found that ZFs are initially driven by the nonlinear self-interaction of the eigenmode. In the nonlinear saturation, the modulational instability becomes important, and its contribution to ZFs can finally be comparable to that of the self-interaction mechanism. More importantly, both types of nonlinear wave-wave interactions can be well described by the turbulent energy flux model.

Automated summary

The nonlinear excitation of zonal flows (ZFs) generated by ion-temperature-gradient turbulence in a tokamak plasma is investigated. It is found that ZFs are initially driven by the nonlinear self-interaction of the eigenmode. In the nonlinear saturation, the contribution of modulational instability becomes important and can be comparable to that of the self-interaction mechanism. Additionally, both types of nonlinear wave-wave interactions can be well described by the turbulent energy flux model.