Electrostatic Oscillations in Plasmas with Cutoff Distributions

When numerically solving the linear Vlasov equation with cutoff electron distributions, the well‐known Landau‐damped oscillation of the electric field was observed first but, after a short transition time, a constant‐amplitude harmonic oscillation with a frequency distinctly higher than Landau's frequency was found. This coexistence of two distinct modes of oscillation—one damped and one undamped—has not been observed before. The behavior is explained quantitatively by comparison of the dispersion equation solution with the results obtained from the numerical solution of Vlasov's equation.