The spin effects on the electromagnetic (EM) wave propagating in arbitrary direction in magnetized plasma are considered. The dispersion relations for EM propagating parallel and perpendicular to the external magnetic field are obtained. It is shown that the spin effects have significant influence on the low frequency modes. New wave modes appear both in left-hand polarized waves propagating parallel to the external magnetic field and in the traditional ordinary waves propagating perpendicular to the external magnetic field. Particularly, the new modes of the latter may exist even in moderate-density magnetized plasmas.

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The nonlinear effects associated with the vacuum polarization and magnetization in the propagation of ultra-intense linearly polarized laser pulse in electron-positron plasmas are investigated. Using the slowly varying envelope approximation, a modified nonlinear Schrödinger equation describing the evolution of the pulse envelope is derived based on the Maxwell equations which include the vacuum polarization and magnetization effects. The analytical and numerical analysis show that the number density of electron-positron plasmas can enhance the vacuum polarization and magnetization effects, and due to the vacuum polarization and magnetization nonlinearity, a one-dimensional laser pulse envelope soliton can be formed. The evolution of an initially Gaussian laser pulse is also discussed by numerical analysis.

This paper investigates the modulational instability of a linearly polarized ultra-intense laser pulse propagating in electron-positron plasmas. Based on the wave equation, which contains vacuum polarization and magnetization effects, the nonlinear dispersion relation and the growth rate of instability are obtained and the effects of plasma number density and laser intensity on the growth rate are analyzed. Numerical results show that if the laser intensity is high enough, the modulational instability growth rate induced by vacuum polarization and magnetization nonlinearity can dominate the modulational instability growth rate induced by the nonlinearity associated with a relativistic effect and ponderomotive force.

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