Langmuir wave linear evolution in inhomogeneous nonstationary anisotropic plasma

TL;DR

This paper derives equations for the linear evolution of Langmuir waves in inhomogeneous, nonstationary, anisotropic plasmas without magnetic fields, highlighting wave action conservation and how wave amplitude scales with electron density.

Contribution

It provides a new theoretical framework for understanding Langmuir wave behavior in complex plasma environments using geometrical optics approximation.

Findings

Wave action density obeys a continuity equation.

Wave amplitude scales as E ~ N^{3/4} in homogeneous plasma.

Wavevector evolution depends on wave geometry.

Abstract

Equations describing the linear evolution of a non-dissipative Langmuir wave in inhomogeneous nonstationary anisotropic plasma without magnetic field are derived in the geometrical optics approximation. A continuity equation is obtained for the wave action density, and the conditions for the action conservation are formulated. In homogeneous plasma, the wave field E universally scales with the electron density N as E ~ N^{3/4}, whereas the wavevector evolution varies depending on the wave geometry.