Velocity spectra V(k) of the Doppler velocity computed from the shift of the Stokes-I signal of the Fe I 5250.2 Å line. In abscissas we use the spherical harmonic wavenumber (m, lower horizontal axis) or the corresponding wavelength λ (upper horizontal axis). Left panel: curves corresponding to the first IMaX time series (dashed black line); second IMaX time series (solid black line) and the HD simulation run (solid green line). Right: curves corresponding to the simulated HD/MHD time series (solid green: HD; solid red: MHD 50 G; dashed orange: MHD 100 G; dashed black: MHD 200 G). The curve corresponding to the second IMaX time series (solid black line) is added for comparison