Mainz 2022 – scientific programme

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P: Fachverband Plasmaphysik

P 22: Helmholtz Graduate School HEPP V

P 22.3: Talk

Friday, April 1, 2022, 14:50–15:15, P-H12

Excitation of High Frequency Waves in Full-6D Kinetic Simulations of Magnetically Confined Plasmas — •Mario Raeth, Klaus Hallatschek, and Katharina Kormann — Max Planck Institute für Plasmaphysik, Garching, Deutschland

Although current gyrokinetic computer simulations are in fair agreement with experimental results in core physics, the assumptions in the derivation make them unreliable in regimes of higher fluctuation amplitudes and stronger gradients, such as the tokamak edge. To correctly describe all phenomena in such regimes, more involved simulations might be necessary. We have developed a novel optimised and scalable semi-Lagrangian solver to simulate ion-temperature gradient modes with the full 6D kinetic equations. It has been verified extensively in the regime of gyrokinetics, including the growth of linear modes and the turbulent saturation. Furthermore, the excitation of high-frequency Bernstein waves (IBWs) has been shown in the non-linear saturation phase. To increase the understanding of the relevance of such high-frequency waves in turbulence, we investigated various excitation mechanisms. Investigations range from non-linear transfer of energy up the frequency scale, to the presence of secondary linear instabilities. The latter lead to a model which allows us to predict a threshold, in the amplitude of a primary gyrokinetic mode, for the excitation and the resulting growth rate of the secondary instability. This helps us to predict the presence and amplitude of IBWs in non-linear ITG simulations, which we could confirm by simulations in our full-6D kinetic code.