Linear and nonlinear modes in nonrelativistic electron-positron plasmas

TLDR

The study develops a comprehensive two‑fluid model to analyze collective modes in a nonrelativistic electron‑positron plasma. The model examines longitudinal and transverse electrostatic and electromagnetic modes, with and without a magnetic field, analyzing their dispersion relations, wave normal surfaces, and cylindrical mirror analyzer Clemmow–Mullaly–Allis diagrams. The study extends the model to two‑stream instability and ion acoustic solitary waves, finding that the instability behaves similarly to electron‑ion plasmas, while solitary waves are only subsonic and their width scales with amplitude rather than speed.

Abstract

A comprehensive two-fluid model is developed for collective modes in a nonrelativistic electron-positron plasma. Longitudinal and transverse electrostatic and electromagnetic modes, both in the presence and absence of a magnetic field, are studied. Wave properties are discussed in terms of dispersion relations, wave normal surfaces, and cylindrical mirror analyzer clemmow-Mullaly-Allis diagrams. The results are extended to include the two-stream instability and ion acoustic solitary waves. For the two-stream instability, a similar result is found as in the electron-ion plasma. For ion acoustic solitary waves, only subsonic solutions are found to exist. Furthermore, their width is proportional to their amplitude, unlike the electron-ion plasma case, where the speed is proportional to the amplitude.