The simplest solutions of cold plasma equations: change in properties from a hydrodynamic to a kinetic model

TL;DR

This paper explores the transition from kinetic to hydrodynamic models in cold plasma by constructing a multi-speed moment chain, revealing significant property changes in solutions when closing the chain at different levels.

Contribution

It introduces a multi-speed moment chain approach to connect kinetic and hydrodynamic models, analyzing how solution properties change with different closures.

Findings

Properties of solutions change significantly when closing the chain at the second step.

Affine and traveling wave solutions exhibit different behaviors compared to standard hydrodynamic models.

Abstract

We consider the transition from the kinetic model of Landau cold plasma to the hydrodynamic one by constructing a "multi-speed" moment chain in the case of one spatial variable. Closing this chain at the first step leads to the standard hydrodynamic system of cold plasma. The change in the properties of the solution when closing the chain at the second step is discussed using the example of two classes of solutions - affine in space and traveling waves, and it is shown that their properties change significantly compared to the hydrodynamic model.