  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 delineate the effects of linear
EGAM drive and finite EGAM amplitude on DW nonlinear dynamic evolution. In
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 regulation of DW by EGAM.
