Waves propagating parallel to the magnetic field in relativistically hot plasmas: A hydrodynamic model with the average reverse gamma factor evolution

Abstract

AbstractThe high‐frequency part of the dispersion dependence of electromagnetic waves propagating parallel to the external magnetic field in the plasma is considered. The plasma is macroscopically motionless, but has relativistic temperatures , where is the electron rest mass and, is the speed of light. The analysis is based on a novel hydrodynamic model based on four equations for the recently developed material fields (Andreev, Phys. Scr., 2022, 97, 085602). These material fields are the concentration, velocity field, average reverse relativistic factor, and the flux of the reverse relativistic factor. In the nonrelativistic regime, there are three transverse waves (the ions are motionless). In this study, we trace the charge of these properties under the influence of relativistic effects. Strong thermal effects lead to a coefficient in front of the cyclotron frequency, which decreases its effective contribution of the cyclotron frequency. At , we have a decrease in the existence area of the fast magneto‐sound wave from the area of large frequencies. However, the existence area of extraordinary waves becomes larger at smaller frequencies. In the strong magnetic field limit , an additional wave appears with a frequency below the thermally decreased cyclotron frequency, where is the electron cyclotron frequency, and is the Langmuir frequency. A further increase in the temperature leads to the disappearance of fast magneto‐sound waves and to a considerable increase in the existence area of the extraordinary waves towards smaller frequencies.