Two-dimensional PIC simulation of collective Thomson scattering in a beam-plasma system

TL;DR

This paper uses 2D PIC simulations to analyze collective Thomson scattering in beam-plasma systems, revealing asymmetries in the scattered wave spectrum related to plasma instabilities and providing insights for interpreting radar and laboratory plasma measurements.

Contribution

It introduces a geometric formulation of the scattered wave spectrum in 2D wave number space and demonstrates spectrum asymmetries caused by plasma instabilities.

Findings

Spectrum becomes asymmetric due to Buneman and ion acoustic instabilities.

Scattered wave spectrum shows asymmetry even in stable, hot beam conditions.

Results aid interpretation of ionospheric radar observations and laboratory CTS measurements.

Abstract

Collective Thomson scattering (CTS) in a beam-plasma system is reproduced by using 2D PIC simulations and the characteristics of the scattered wave spectrum are examined. By formulating the geometric shape of the scattered wave spectrum in wave number space, where the velocity vector of the beam component and the wave vectors of the incident and scattered waves are arbitrary, it is demonstrated that the spectrum in 2D wave number space becomes asymmetric. The spectrum of scattered waves propagating in a specific direction is presented as a function of wavelength to show that the electron (ion) feature is amplified and becomes asymmetric or distorted when Buneman (ion acoustic) instability occurs. An additional simulation is conducted for a weak, linearly stable beam-plasma system with a hot beam, and confirmed that the obtained scattered wave spectrum shows asymmetric feature. The results are expected to be applicable to the interpretation of radar observations of ionospheric plasmas as well as CTS measurements in laboratory plasmas.