Dynamic structure factor and excitation spectrum of the one-component plasma: the case of weak to moderate magnetization

TL;DR

This study uses molecular dynamics simulations to explore how weak to moderate magnetic fields influence the collective density modes and excitation spectrum of strongly coupled one-component plasmas, revealing new Bernstein modes and mode modifications.

Contribution

It extends previous work by demonstrating the presence of Bernstein modes in weakly magnetized regimes and analyzing the impact of small magnetization on plasma mode dispersion and damping.

Findings

Bernstein modes observed below the upper hybrid frequency in weakly magnetized plasmas.

Small magnetization induces a strong zero-frequency mode perpendicular to the magnetic field.

Magnetization alters the dispersion and damping of the upper hybrid mode.

Abstract

Magnetized plasmas are well known to exhibit a rich spectrum of collective modes. Here, we focus on the density modes in dense or cold plasmas, where strong coupling effects alter the mode spectrum known from traditional weakly coupled plasmas. In particular, we study the dynamic structure factor (DSF) of the magnetized one-component plasma with molecular dynamics simulations. Extending our previous results [H.~K\"ahlert and M.~Bonitz, Phys. Rev. Research \textbf{2022}, 4, 013197], it is shown that Bernstein modes can be observed in the weakly magnetized regime, where they are found below the upper hybrid frequency, provided the coupling strength is sufficiently low. We investigate the DSF for a variety of different wave numbers and plasma parameters and show that even small magnetization can give rise to a strong zero-frequency mode perpendicular to the magnetic field and change the dispersion as well as the damping of the upper hybrid mode.