Flux distribution of initial and final states during wave–particle interaction, corresponding to electrons with energy 0.05–0.6 MeV and L shell value 1.4–2.0. Other parameter values: wave frequency ω/(2π) = 19.8 kHz, wave amplitude δb = 200 pT, semiband width 500 Hz, and N₀ = 3000 counts/s. The DEMETER and NOAA satellite observation ranges from 0.3 rad to 0.44 rad.