Diffusive Radiation in One-dimensional Langmuir Turbulence

TL;DR

This paper analyzes the radiation spectra of relativistic particles in one-dimensional Langmuir turbulence, revealing how the spectrum shape depends on particle motion angle and identifying features relevant to astrophysical and laboratory plasmas.

Contribution

It provides a detailed calculation of radiation spectra in Langmuir turbulence, highlighting the dependence on particle velocity angle and spectrum complexity for oblique propagation.

Findings

Spectrum shape varies with particle velocity angle.

Transverse motion yields a degenerate spectrum similar to uniform oscillations.

Oblique propagation produces complex spectra with power-law regions and potential high-frequency peaks.

Abstract

We calculate spectra of radiation produced by a relativistic particle in the presence of one-dimensional Langmuir turbulence which might be generated by a streaming instability in the plasma, in particular, in the shock front or at the shock-shock interactions. The shape of the radiation spectra is shown to depend sensitively on the angle between the particle velocity and electric field direction. The radiation spectrum in the case of exactly transverse particle motion is degenerate and similar to that of spatially uniform Langmuir oscillations. In case of oblique propagation, the spectrum is more complex, it consists of a number of power-law regions and may contain a distinct high-frequency spectral peak. %at $\omega=2\omega\pe \gamma^2$. The emission process considered is relevant to various laboratory plasma settings and for astrophysical objects as gamma-ray bursts and collimated jets.