The Solitary Dispersive Alfven Wave in a Plasma with Two Distinct Electron Groups

摘要

The electromagnetic polarization and the nonlinear soliton structure of dispersive Alfven waves (DAWs) in a plasma with two different electron groups are investigated from the viewpoint multi-component fluid theory where the hot superthermal electron component is modeled by the kappa distribution. With the increase in the cold electron concentration, the electromagnetic polarization of DAW changes from the ones similar to the kinetic Alfven wave to the ones similar to the inertial Alfven wave. Meanwhile, the influence of the superthermal spectral index on the properties of DAW is reduced. Under the small amplitude assumption we find that there will be a soliton structure with positive potential amplitude. Correspondingly, the density of superthermal electrons will increase, while the density of cold electrons is decreased. But the total density variation strongly depends on the soliton velocity, the concentration of the cold electrons, and the value of kappa. The plausible application to the plasma sheet boundary layer is discussed from the numerical calculation of the nonlinear governing equation.