Effect of the electron redistribution on the nonlinear saturation of Alfv\'en eigenmodes and the excitation of zonal flows

TL;DR

This study uses numerical simulations to explore how electron redistribution influences the nonlinear saturation of Alfvén eigenmodes and the excitation of zonal flows in a plasma with a reversed shear magnetic field.

Contribution

It demonstrates the significant role of electron population redistribution in increasing BAE saturation levels and zonal flow amplitudes in nonlinear plasma dynamics.

Findings

Electron redistribution enhances BAE saturation.

Zonal flow amplitudes are increased by electron effects.

Nonlinear wave-particle interactions are crucial in plasma behavior.

Abstract

Numerical simulations of Alfv\'en modes (AM) driven by energetic particles are performed with the GK global PIC code ORB5. A reversed shear equilibrium magnetic field is adopted. A simplified configuration with circular flux surfaces and large aspect ratio is considered. The nonlinear saturation of beta-induced Alfv\'en eigenmodes (BAE) is investigated. The roles of the wave-particle nonlinearity of the different species, i.e. thermal ions, electrons, and energetic ions are described, in particular for their role in the saturation of the BAE and the generation of zonal flows. The nonlinear redistribution of the electron population is found to be important in increasing the BAE saturation level and the zonal flow amplitude.