One-dimensional power spectrum of the charge density ρ_c along the horizontal direction x, computed for the magnetised multiwavelength simulations at an equivalent non-linear stage defined by ∆h/L_x ≃ 0.35. All spectra were obtained using the same spectral procedure and are normalised by their maximum value. The different curves correspond to increasing ion-neutral coupling strength and are labelled NC, LC, IC, and HC (see Sect. 3). The vertical dashed lines indicate the minimum and maximum injected wavenumbers, as well as half the Nyquist limit.