Gyrokinetic and kinetic-MHD simulations of n=1 fishbone modes in DIII-D plasmas find that self-generated zonal flows can dominate the fishbone saturation. The saturation mechanism is identified in phase space, where the zonal flows prevent holes and clumps from persisting or drifting in phase space with mode down-chirping, reducing the wave-particle resonant drive. This saturation is confirmed by quantitative agreement with experimental measurements for both mode saturation amplitude and neutron emissivity. Zonal flows shearing rate exceeds the drift-wave growth rate, consistent with the ITB observed in DIII-D plasmas. The deliberate destabilization of fishbones for the development of high performance scenarios in ITER is then proposed.
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