On zero frequency zonal flow and second harmonic generation by finite amplitude energetic particle induced geodesic acoustic mode

摘要

The nonlinear self-interaction of finite amplitude energetic particle induced geodesic acoustic modes (EGAMs) is investigated using the nonlinear gyrokinetic theory. It is found that both zero frequency zonal flow (ZFZF) and second harmonic can be driven by finite amplitude EGAMs, with energetic particles (EPs) playing a dominant role in the nonlinear couplings through finite orbit width effects. For ZFZF, the effects of EPs on EGAM nonlinear self-coupling dominate those of the thermal plasmas which are also present, while the second harmonic generation is only possible via finite amplitude coupling through EPs. Our findings may improve the understanding of stabilizing zonal modes and consequently drift wave turbulence. Published by AIP Publishing.