Generation of magnetic field fluctuations in relativistic electron–positron magnetoplasmas

It is shown that magnetic field aligned equilibrium relativistic plasmas flows can excite electromagnetic fluctuations in a magnetized electron–positron (e–p) plasma. For this purpose, a new dispersion relation is derived by using a relativistic two-fluid model and the Maxwell equations. The dispersion relation admits purely growing instabilities of electromagnetic perturbations across the ambient magnetic field direction. The results have relevance for understanding the origin of magnetic field fluctuations in cosmological and laser-produced plasmas.