Preferential acceleration and magnetic field enhancement in plasmas with e⁺/e⁻ beam injection

A theoretical model of current filaments predicting preferential acceleration/deceleration and magnetic field enhancement in a plasma with e⁺/e⁻ beam injection is presented. When the e⁺/e⁻ beams are injected into a plasma, current filaments are formed. The beam particles are accelerated or decelerated depending on the types of current filaments in which they are trapped. It is found that in the electron/ion ambient plasma, the e⁺ beam particles are preferentially accelerated, while the e⁻ beam particles are preferentially decelerated. The preferential particle acceleration/deceleration is absent when the ambient plasma is the e⁺/e⁻ plasma. We also find that the particle momentum decrease can explain the magnetic field increase during the development of Weibel/filamentation instability. Supporting simulation results of particle acceleration/deceleration and magnetic field enhancement are presented. Our findings can be applied to a wide range of astrophysical plasmas with the e⁺/e⁻ beam injection.