Generalized slab universal instability and its appearance in pair plasma

TL;DR

This paper derives a comprehensive dispersion relation for electromagnetic slab universal modes, incorporating ion charge, electron FLR, and Debye effects, revealing stability conditions in pair plasmas and wider applicability.

Contribution

It introduces a generalized dispersion relation for slab universal modes that includes ion charge, electron FLR, and Debye shielding effects, expanding predictive accuracy and applicability.

Findings

Electron FLR effects weakly stabilize the instability.

Debye shielding strongly stabilizes as $ ho_D$ approaches $ ho_i$.

Instability persists in pair plasmas above a critical density.

Abstract

A generalized linear dispersion relation of electromagnetic slab universal modes is derived, taking into account arbitrary ion charge state, electron finite Larmor radius (FLR) effects, and Debye shielding effects. As a consequence, it provides more accurate predictions and is applicable to a wider range of plasmas. We find that electron FLR effects have a weakly stabilizing effect on the slab universal instability in electron-ion plasma, while Debye shielding strongly stabilizes this instability when $\lambda_D$ approaches $\rho_i$ ($\lambda_D$ is the Debye length and $\rho_i$ is the ion gyro-radius). In particular, we examine the stability criterion for this instability in electron-positron pair plasmas, and find that the instability persists in this simplest plasma system as long as the pair plasma number density exceeds the critical value $n_c=B^2/(8\pi m_e c^2)$.