Symmetries and charge neutrality of electromagnetic solitons in perfect pair plasmas

Abstract

The properties of parallel propagating large amplitude electromagnetic solitons are investigated in a thermal, magnetized pair plasma. These solitons are proven to be charge neutral and to have a linearly polarized magnetic but no electric field. From a Sagdeev pseudopotential analysis it transpires that such solitons are compressive in the species densities and destroyed when the species’ sound velocity exceeds a fraction of their Alfvén speed. The existence domain in compositional parameter space shows maxima for the soliton Mach numbers, densities and perpendicular magnetic field components. These maxima depend on the ratio between thermal and Alfvén velocities and do not themselves correspond to physically valid solutions. A short discussion is given about possible generalizations, and the assumptions required for that.