Pattern formation and spatiotemporal chaos in relativistic degenerate plasmas

TL;DR

This paper investigates how high-frequency EM waves interact with low-frequency density perturbations in relativistic plasmas, revealing pattern formation, chaos, and turbulence that influence astrophysical radiation spectra.

Contribution

It introduces a numerical study of nonlinear wave interactions in relativistic degenerate plasmas, highlighting the emergence of incoherent states and chaos due to modulational instability.

Findings

Multiple solitary patterns can form through modulational instability.

The system exhibits temporal and spatiotemporal chaos confirmed by Lyapunov spectra.

Wave energy redistributes from large-scale patterns to incoherent small-scale turbulence.

Abstract

We numerically study the nonlinear interactions of high-frequency circularly polarized electromagnetic (EM) waves and low-frequency electron-acoustic (EA) density perturbations driven by the EM wave ponderomotive force in relativistic plasmas {(moderate, strong, and ultra-relativistic)} with two groups of electrons--the population of relativistic degenerate dense electrons (bulk plasma) and the sparse relativistic nondegenerate (classical) electrons, and immobile singly charged positive ions. By pattern selection, we show that many solitary patterns can be generated and drenched through modulational instability of EM waves at different spatial length scales and that the EM wave radiation spectra emanating from compact astrophysical objects may not settle into stable envelope solitons but into different incoherent states, including the emergence of temporal and spatiotemporal chaos due to collisions and fusions among the patterns with strong EA wave emission. The appearance of these states is confirmed by analyzing the Lyapunov exponent spectra, correlation function, and mutual information {as quantitative evidence}. As a result, the redistribution of wave energy from initially exciting many solitary patterns at large scales to a few new incoherent patterns with small wavelengths in the system occurs, leading to the onset of turbulence in astrophysical plasmas.