Abstract
Coulomb collisions at rate ν produce slightly probabilistic rather than fully deterministic charged particle trajectories in weakly collisional plasmas. Their diffusive velocity scattering effects on the response to a wave yield an effective collision rate νeff ≫ ν and a narrow dissipative boundary layer for particles with velocities near the wave phase velocity. These dissipative effects produce temporal irreversibility for times t ≳ 1/νeff during Landau damping of a small amplitude Langmuir wave.
Highlights
In a classic theoretical physics paper,1 Landau used a Laplace transform to introduce causality into the process of determining the time-asymptotic linear plasma response to a wave perturbation
Coulomb collisions at rate produce slightly probabilistic rather than fully deterministic charged particle trajectories in weakly collisional plasmas. Their diffusive velocity scattering effects on the response to a wave yield an effective collision rate eff ) and a narrow dissipative boundary layer for particles with velocities near the wave phase velocity. These dissipative effects produce temporal irreversibility for times t տ 1=eff during Landau damping of a small amplitude Langmuir wave
Entropy-producing process because: collisional effects are not involved in the derivation; the damping rate is independent of the collision rate; and the wave damping seems to imply irreversibility
Summary
In a classic theoretical physics paper, Landau used a Laplace transform to introduce causality into the process of determining the time-asymptotic linear plasma response to a wave perturbation This produced what is known as Landau damping of the wave, which has been confirmed experimentally.. D$iffpusffiffieffi?ffiffiffisffitffih(e pitch-angle 1 and cause through a a typically spmffiaffiffilffiffilffieffiffirffiffi diffusive spread in the speed dv=v0 ðv0 À vÞ=v0 $ 2 ks These Coulomb collisional scattering effects are operative in and intrinsic to most weakly collisional plasmas. Collisional effects on the time-asymptotic Landau damping of a Langmuir (electron plasma) wave have been explored using speed-diffusion-based collision operators that neglect the pitch-angle scattering effects of Coulomb collisions. This paper introduces a novel Green function procedure for incorporating short time scale (s ( 1/) velocity scattering effects of Coulomb collisions on electron trajectories after a small amplitude Langmuir wave is imposed.
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