Filamentation instability of ion-acoustic waves driven by a scattered relativistic beam

Ion-acoustic instability driven by a scattered relativistic beam propagating in a plasma of hot and cold ions is investigated. We have derived a fully electromagnetic dispersion relation and its cold beam limit and discussed the general features of the growth rate spectrum. We find that this instability is sensitively damped by the beam temperature. Particle trapping and nonlinear growth are studied by using particle-in-cell simulations.