The electromagnetic counterstreaming instability in unmagnetized pair (electron-positron) plasmas which is influenced by the external magnetic field paralled to the streaming direction is investigated numerically. The simulation show that the counterstreaming instability changes its character from magnetic to electrostatic nature. The electrostatic waves growing due to the electrostatic counterstreaming instability play an important role for producing fast electrons and positrons with energy of MeV. The process of high-energy particle production in relativistic shocks in magnetized pair plasmas may be applied to gamma-ray burst events.
Saito et al. (Mon,) studied this question.