Outgoing FMS wave luminosity injected by short-envelope Alfvén waves. We compare counter-propagating Alfvén waves (b _eq ≈ 0.39, cT/λ = 0.5, λ = R _*/2, θ _s = 45°) of different phases (black/blue lines) and varying sizes of the injection region (top: Δθ = 20°; bottom: Δθ = 5°) with the FMS wave injected by a single Alfvén wave (red lines). The inset shows a zoom into the initial interaction period, where the phase difference induces different FMS wave luminosities.