Dynamic evolutions of multiple toroidal Alfvén eigenmodes with energetic particles

Kinetic simulations based on a reduced model are carried out to study dynamic evolutions of multiple toroidicity-induced shear Alfvén eigenmodes driven by energetic particles. It is found that passing and trapped particles play quite different roles on the mode evolution. For cases without background damping, passing particles lead to a longer linear growth phase and subsequent enhancement of the nonlinear saturation level when resonant regions with two modes are closely overlapped. On the other hand, trapped particles are mainly responsible for the persistent mode growth in the nonlinear phase. By comparing the results from anisotropic and isotropic simulations, it is suggested that passing particles have a negative impact on the mode development in the nonlinear phase. For the near marginal stability cases with large background damping, the upward and downward frequency chirping in multiple branches are significantly affected by the multi-mode interaction due to overlapping of hole and clump in the distribution function