The non-linear evolution of spin-electron acoustic, positron-acoustic, and spin-electron-positron acoustic waves is considered. It is demonstrated that weakly nonlinear dynamics of each wave leads to the soliton formation. Altogether, we report on existence of three different solitons. The spin-electron acoustic soliton known for electron-ion plasmas is described for electron-positron-ion plasmas for the first time. The existence of the spin-electron-positron acoustic soliton is reported for the first time. The positron-acoustic soliton and the spin-electron-positron acoustic soliton arise as the areas of a positive electric potential. The spin-electron acoustic soliton behaves as the area of a negative electric potential at the relatively small positron imbalance n0p/n0e = 0.1 and as the area of a positive electric potential at the relatively large positron imbalance n0p/n0e = 0.5.
We consider the separate spin evolution of electrons and positrons in electron-positron and electron-positron-ion plasmas. We consider oblique propagating longitudinal waves in this systems. Working in a regime of high density n0 ∼ 10 27 cm −3 and high magnetic field B0 = 10 10 G we report presence of the spin-electron acoustic waves and their dispersion dependencies. In electron-positron plasmas, similarly to the electron-ion plasmas, we find one spin-electron acoustic wave (SEAW) at propagation parallel or perpendicular to the external field and two spin-electron acoustic waves at the oblique propagation. At the parallel or perpendicular propagation of the longitudinal waves in electron-positron-ion plasmas we find four branches: the Langmuir wave, the positron-acoustic wave and pair of waves having spin nature, they are the SEAW and, as we called it, spin-electron-positron acoustic wave (SEPAW). At the oblique propagation we find eight longitudinal waves: the Langmuir wave, Trivelpiece-Gould wave, pair of positron-acoustic waves, pair of SEAWs, and pair of SEPAWs. Thus, for the first time, we report existence of the second positron-acoustic wave existing at the oblique propagation and existence of SEPAWs.
Using nonrelativistic spin quantum fluid theory, parallel propagating electromagnetic waves in electron-positron plasma immersed in a uniform external magnetic field have been investigated. With the inclusion of the spin effect of the plasma species, Faraday rotation appears, which is absent in usual electron-positron plasmas without spin effects. New resonance frequencies and extra cutoffs are observed for both right-hand and left-hand circularly polarized waves.
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