Nonlinear dynamics of beta induced Alfv\'en eigenmode driven by energetic particles

TL;DR

This paper investigates the nonlinear saturation behavior of beta induced Alfvén eigenmodes driven by energetic particles, revealing frequency chirping, symmetry breaking, and resonance detuning effects through advanced simulations.

Contribution

It provides new insights into the nonlinear dynamics and saturation mechanisms of Alfvén eigenmodes driven by energetic particles using a hybrid MHD gyro-kinetic code.

Findings

Frequency chirping observed during saturation

Symmetry breaking between co- and counter-passing particles

Saturation amplitude scales with growth rate consistent with radial resonance detuning

Abstract

Nonlinear saturation of beta induced Alfv\'en eigenmode, driven by slowing down energetic particles via transit resonance, is investigated by the nonlinear hybrid magnetohyrodynamic gyro-kinetic code (XHMGC). Saturation is characterized by frequency chirping and symmetry breaking between co- and counter-passing particles, which can be understood as the the evidence of resonance-detuning. The scaling of the saturation amplitude with the growth rate is also demonstrated to be consistent with radial resonance detuning due to the radial non-uniformity and mode structure.