The enhanced soliton propagation and energy transfer in the coupled drift wave and energetic-particle-induced geodesic acoustic mode system

Abstract

The evolution of the coupled drift wave (DW) and energetic-particle-induced geodesic acoustic mode (EGAM) nonlinear system is investigated using the fully nonlinear coupled DW-EGAM two-field equations with emphasis on the turbulence spreading in the form of soliton and the nonlinear energy transfer between DW and EGAM. Four scenarios with different combinations of EGAM initial amplitudes and linear EGAM growth rates are designed to clarify the contributions of linear excitation of EGAM by EPs and nonlinear excitation by DWs to the nonlinear evolution. In the presence of the linear EPs drive, the soliton propagation is enhanced, due to the generation of small radial scale structures. Two conservation laws of the nonlinear system are derived, including the energy conservation law. It is found that the energy of DW always decreases and that of EGAM always increases, leading to the regulation of DW by EGAM.