Propagation of electromagnetic solitons in nonequilibrium dispersive media

We establish the possibility of the existence of stationary solitary electromagnetic waves in nonequilibrium plasma-beam systems. We show that the propagation of wave packets in resonance with the plasma (the retarding medium) or the beam is not accompanied by a dispersive smearing of the plasma. We determine the conditions for the existence of solitons, find their characteristics, and give a physical interpretation of the solutions obtained. As a concrete example we consider a helicon soliton in a plasma penetrated by an ion beam