Solitary dispersive Alfven wave in a plasma with hot electrons, cold positrons and ions

The dispersion relation and the nonlinear behaviour of dispersive Alfven waves (DAWs) in a plasma, which is composed by hot electrons, cold positrons and ions, are studied from the multi-component fluid theory. It can be indicated from the linear dispersion relation that the coupling of positron acoustic waves with shear Alfven waves results from the effect of the finite ion gyroradius. In our mode, the pressure and the inertia of the positron acoustic wave are, respectively, provided by the hot electrons and the cold positrons, which are different from the ones in a plasma consisting of two-group positrons with different temperatures. Furthermore, the existence and properties of DAW solitons are analysed from the Sagdeev pseudopotential equation, which indicates the existence of super-Alfvenic or sub-Alfvenic solitary DAWs, as well as the amplitude and width of DAW solitons depend on the positron concentration and the electron temperature. When the effects of cold positrons can’t be neglected, there may coexist the compressive and rarefactive DAW solitons. When the concentration of positron is negligibly small, the properties of DAW solitons in our model are similar to the ones of kinetic Alfven wave solitons in a plasma composed by hot electrons and cold ions.