Solitary dispersive Alfvén wave in a plasma composed of hot positrons, cold electrons and ions

The nonlinear solitary structure of the dispersive Alfvén wave in an three-component plasma with hot positron, cold electron and ion is studied from the multi-fluid theory. It is found that when the equilibrium number density ratio of ion to electron is finite, there only exists the super-Alfvén rarefactive solitons. The increase of the ion concentration or the speed of soliton will lead a deeper depletion of the electron number density. The width of soliton decreases with the increase of the speed of soliton and the ion concentration. When the equilibrium number density ratio of ion to electron is much less than unity, there are only sub-Alfvén rarefactive solitons. In the case, the larger speed of soliton or the smaller concentration of ions result the deeper depletion of the electron number density. The width of the soliton increases with the ion concentration and the speed of soliton. The results obtained may be related to the observations and experimental results in the electron positron plasma.