Fourier amplitudes of the y-velocities. The amplitudes are averaged in height between –0.375 and 0.375, the same height shown in Figs. 13 and 14. The vertical dotted black line located at n = 145 corresponds to the mode corresponding to the collision frequency between neutrals and ions, calculated from Eq. (44). For an improved visualization, the upper limit on the x-axis is 512 for “cada3” limiter, and 1600 for “mp5” limiter. Both limiters show decoupling at small scales in the velocity.