Periodic waves in ultrarelativistic inhomogeneous electron-positron-ion plasma

College of Physics and Electronics Engineering, Northwest Normal University - Lanzhou 730070, China

^(a) xuejk@nwnu.edu.cn

Received: 4 June 2013
Accepted: 19 August 2013

Abstract

The nonlinear interaction of ultrarelativistic intense electromagnetic/electrostatic waves and homogeneous/inhomogeneous electron-positron-ion (e-p-i) plasma are investigated. Starting from the relativistic fluid-Maxwell model, we show that the system of the governing equations can be reduced to two modified canonical equations with inhomogeneity effect. It is found that periodic wave solutions can exist in both homogeneous and inhomogeneous e-p-i plasma. However, periodic solutions can exist in inhomogeneous e-p-i plasma only when the positron density is above a critical value. The critical positron density for exciting the periodic waves strongly depends on both the inhomogeneity nature and the phase velocity of the wave. Furthermore, the topology structure of the phase space is simplified and only circular solutions can exist when the positron density is high enough.