Comparison of linear modes in kinetic plasma models

TL;DR

This paper systematically compares linear theory results from hybrid, gyrokinetic, and fully-kinetic plasma models using a solar wind turbulence test case, aiding model selection in complex plasma regimes.

Contribution

It provides a comprehensive comparison of different kinetic plasma models for solar wind turbulence, highlighting their applicability and differences in linear mode predictions.

Findings

Hybrid, gyrokinetic, and fully-kinetic models show varying spectral properties.

Low-frequency mode comparisons depend on propagation angles.

Results guide model choice in non-trivial plasma regimes.

Abstract

We compare, in an extensive and systematic way, linear theory results obtained with the hybrid (ion-kinetic and electron-fluid), the gyrokinetic and the fully-kinetic plasma models. We present a test case with parameters that are relevant for solar wind turbulence at small scales, which is a topic now recognized to need a kinetic treatment, to a certain extent. We comment on the comparison of low-frequency single modes (Alfv\'{e}n/ion-cyclotron, ion-acoustic, and fast modes) for a wide range of propagation angles, and on the overall spectral properties of the linear operators, for quasi-perpendicular propagation. The methodology and the results presented in this paper will be valuable when choosing which model should be used in regimes where the assumptions of each model are not trivially satisfied.