Electron distribution f( v) (upper plots), and Langmuir wave spectral energy density W( k) (lower plots) for homogeneous (top left) and inhomogeneous plasma, with q ₀ = 10 ⁻⁴ k _de , v ₀/ v _Te = 0.3 and of 3.7 × 10 ⁻⁴ (top right), 3.7 × 10 ⁻³ (bottom left), and 1.2 × 10 ⁻² (bottom right). Lines from dark (blue in online version) to light show the beam relaxation during the first 10 quasilinear times, while the thick line (red in online version) shows the state reached at t = 100τ _ql.