Nonlinear wavenumber of an electron plasma wave

Abstract

The wavenumber of a large-amplitude electron plasma wave propagating on a collisionless plasma column is measured. The wavenumber is shifted from that of a small-amplitude wave of the same frequency. This nonlinear wavenumber shift, δkr, depends on position, frequency, and initial wave amplitude, Φ. The observed spatial oscillations of δkr agree qualitatively with recent theories. Experimentally δkr∝kiS (Φ) √Φ where ki is the linear Landau damping coefficient, S (Φ) ≡ki(Φ)/ki, and ki(Φ) is the initial damping coefficient which depends on Φ.