Nonlinear dynamics of nonadiabatic chirping-frequency Alfven modes in tokamak plasmas

Frequency chirping of Alfven modes, a phenomenon observed in tokamak fusion plasmas driven by energetic particles (EPs), can result in significant losses of EPs. In this study, we use the global gyrokinetic code ORB5 (Lanti et al 2020 Comput. Phys. Commun. 251 107072) to investigate the nonlinear dynamics of non-adiabatic frequency chirping EP modes (EPMs). Our results illuminate non-perturbative features of EPMs caused by the presence of EPs. Additionally, we find that, with a fixed safety factor profile and a single toroidal mode number, the frequency chirping rate is linearly proportional to the mode saturation amplitude, as predicted by the theory (Chen and Zonca 2016 Rev. Mod. Phys. 88 015008).

Automated summary

In this study, we investigate the nonlinear dynamics of non-adiabatic frequency chirping energetic particle modes using the global gyrokinetic code ORB5. Our results reveal the non-perturbative features of these modes and confirm the linear relationship between the frequency chirping rate and mode saturation amplitude.