Saturation mechanisms at play in the two simulations: ion trapping (left panels) and current relaxation (right panel). Left panels: isocontour of the ion phase space density (top panel) together with the electric potential of the LHDI waves (bottom panel) on the same spatial axis, both quantities being computed in the unstable layer. Right panel: evolution of the difference between the average charged current in the unstable layer (2 < x < 4) and its value at t = 0, for both simulations.