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

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.

Automated summary

In this study, the ion-acoustic features of collective Thomson scattering (CTS) in two-stream plasmas are investigated both theoretically and numerically. The theoretical spectrum shows asymmetry when the electron distribution functions of the stationary and moving components overlap with each other at the phase velocities corresponding to the two resonant peaks. Numerical simulations confirm the theoretical spectra and also demonstrate the effect of a two-stream-type instability in the ion-acoustic feature. The results highlight the significant effects of two-stream plasmas on CTS spectra and the observation of waves resulting from instabilities in the ion-acoustic feature.