Ion-acoustic solitons in a plasma with a relativistic electron beam

Ion-acoustic solitons in a collisionless plasma consisting of warm ions, hot isothermal electrons, and a relativistic electron beam are studied by using the reductive perturbation method. The basic set of fluid equations is reduced to Korteweg-de Vries (KdV) and modified Korteweg-de Vries (mKdV) equations. The effects of ion temperature and relativistic electron beam on ion-acoustic solitons are investigated. It has been shown that the four ion-acoustic modes can be propagated in this plasma system. The compressive and rarefactive ion-acoustic solitons satisfies the KdV equation for a given soliton velocity, beam density much smaller than the background electron density and the bulk ion temperature smaller than the background electron temperature for two modes. Also it has been illustrated that there exist mKdV solitons for some critical value of electron beam density in these cases. These critical values decrease as ion temperature increases for one of two modes and increase for the other one. Finally, it has been remarked that for another two modes only rarefactive KdV ion-acoustic solitons can be obtained. One of these modes exists for the electron beam density much smaller than the bulk electron density, and the other exists for almost all values of the beam density, even if it is greater than the background electron density. (C) 2001 American Institute of Physics.