Plasma Oscillations (Langmuir Waves)

1D jellium model — electrons displaced from positive background, Langmuir frequency ωₚ
ωₚ = √(ne²/ε₀mₑ)  |  Electrons oscillate at plasma frequency regardless of wavelength (electrostatic mode)
Electron density ρ(x) — blue = depleted, orange = compressed
Electric field E(x)
Phase space (x, v)