Electron Fishbone Simulations in FTU-Like Equilibria Using XHMGC

Abstract. This work discusses the first numerical simulation results of fishbone excitation by a suprathermal electron population due to, e.g., electron cyclotron resonance heating and/or lower hybrid wave current drive. The precession resonance underlying the linear instability is clearly identified. Meanwhile, mode saturation is shown to occur because of the secular resonant particle motion, pumping particles out of the radial region where the wave-particle power exchanged is initially localized. The mode nonlinear saturation is accompanied by downward frequency chirping, due to phase-locking of the mode with resonant particles, consistent with the “mode particle pumping” mechanism. Additional frequencies and mode structure patterns emerge in the late nonlinear phase of the fluctuation evolution.