Emission from a soliton in a resonant field

The radiant power of plasma waves emitted by a fluxon in a long Josephson junction under the action of an impressed alternating current with a frequency close to the plasma frequency of the contact is calculated, along with the power of spin waves emitted by a quasione-dimensional domain wall in a weak easy-plane ferromagnet under the action of an external magnetic field with a frequency close to parametric resonance. The resonant emission from small-amplitude breathers (dynamical solitons) and the emission from a breather in a weak ferromagnet under the action of a randomly varying field are investigated. The investigation is carried out by a perturbation theory based on the inverse-scattering method for the sine–Gordon equation, in which the external field plays the role of a small perturbation.