Short-wavelength soliton in ultrarelativistic electron-positron-ion plasmas

TL;DR

This paper derives a nonlinear equation for short-wavelength waves in ultrarelativistic electron-positron-ion plasmas, highlighting the role of ions in nonlinearity and demonstrating elastic collisions between solitons through simulations.

Contribution

It presents a new nonlinear equation based on the Vlasov approach for ultrarelativistic plasmas, extending previous nonrelativistic models and emphasizing ion effects.

Findings

Nonlinear equation derived for ultrarelativistic plasmas.

Ion presence is essential for nonlinearity.

Soliton collisions are fully elastic in simulations.

Abstract

We derive a nonlinear equation governing dynamics of short-wavelength longitudinal waves in ultrarelativistic electron-positron-ion plasmas. In contrast to the recent work by Lashkin [Phys. Plasmas {\textbf{27}}, 102302 (2020)], where a similar equation was suggested in the framework of the Wigner function approach for a nonrelativistic electron-ion degenerate plasma, in our case which is based on the Vlasov kinetic equation all three species of particles (electrons, positrons and ions) should be present. The nonlinearity arises only in the presence of a population of ions. By numerical simulations we demonstrate that collisions between even four solitons are fully elastic.