Alfvén soliton and emitted radiation in the presence of perturbations.

Soliton perturbation theory based on the inverse scattering transform method is applied to the derivative nonlinear Schrödinger equation, which describes nonlinear Alfvén waves propagating quasiparallel to the external magnetic field. Radiative effects are considered. Spectral distributions of the emitted energy and magnetic helicity rates (in the wave number domain) are calculated analytically. Several forms of perturbations are considered, including the finite electric conductivity, the effect of resonant particles (nonlinear Landau damping), and the influence of the random inhomogeneity of the plasma density. The space structure of the radiative field is determined for a perturbation in the form of the finite electric conductivity.