Snapshots of the velocity distribution of the simulations with n_e/n₀ = 10%. The distributions are obtained at t = 0 (panel a), 150 (panel b), and 300 (panel c). The white curve in panel a is the resonant curve of the Z, X2, and X3 modes amplified at 90°, with ω = 0.96 Ω_ce (n = 1), ω = 1.92 Ω_ce (n = 2), and ω = 2.88 Ω_ce (n = 3). An animation of this figure is available online starting at t = 0 and ending at 300 .