Ion-acoustic feature of collective Thomson scattering in non-equilibrium two-stream plasmas

TL;DR

This paper explores how two-stream plasma interactions influence collective Thomson scattering spectra, revealing asymmetries and instability effects that can be observed experimentally.

Contribution

It provides a theoretical and numerical analysis of ion-acoustic features in two-stream plasmas, highlighting the impact of electron distribution overlaps and instabilities on CTS spectra.

Findings

Asymmetry in spectra due to electron Landau damping differences

Agreement between numerical simulations and theoretical spectra

Observation of instability effects causing spectral asymmetry

Abstract

We theoretically and numerically investigate the ion-acoustic features of collective Thomson scattering (CTS) in two-stream plasmas. When the electron distribution functions of two (stationary and moving) components overlap with each other at the phase velocities corresponding to the two resonant peaks of the ion-acoustic feature, the theoretical spectrum shows asymmetry because the rate of electron Landau damping is different for the two peaks. The results of numerical simulations agree well with the theoretical spectra. We also demonstrate the effect of a two-stream-type instability in the ion-acoustic feature. The simulated spectrum in the presence of the instability shows an asymmetry with the opposite trend to the overlapped case, which results from the temporal change of the electron distribution function caused by the instability. Our results show that two-stream plasmas have significant effects on CTS spectra and that the waves resulting from instabilities can be observed in the ion-acoustic feature.