Nonlinear reversed shear Alfvén eigenmode saturation due to spontaneous zonal current generation

2021/09/22 by Shizhao Wei, Tao Wang, Ningfei Chen +1
Physics and Astronomy · #Ionosphere and magnetosphere dynamics #Magnetic confinement fusion research #Solar and Space Plasma Dynamics

paper · pdf · doi:10.1017/s0022377821000908

Abstract

General nonlinear equations describing reversed shear Alfvén eigenmode (RSAE) self-modulation via zero-frequency zonal structure (ZFZS) generation are derived using nonlinear gyrokinetic theory, which are then applied to study the spontaneous ZFZS excitation as well as RSAE nonlinear saturation. It is found that both electrostatic zonal flow and electromagnetic zonal current can be preferentially excited by finite-amplitude RSAE, depending on specific plasma parameters. The modification to local shear Alfvén wave continuum is evaluated using the derived saturation level of zonal current, which is shown to play a comparable role in saturating RSAE with the ZFZS scattering.

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