Reynolds and magnetic Reynolds numbers as a function of height and kinetic and magnetic energy spectra. Left: time-averaged profiles of Re_eff(t, z) as function of geometrical height z for the simulations h12, h6, h6ν_H, and h6ν_S. Centre: time-averaged profiles of Re_m, eff(t, z) for the simulations h12, h6, and h6η_H. Right: Spectra of (solid lines) and (dashed lines) averaged over time and in space between z = −200 km and z = 0 km as a function of horizontal wave number k_h. The spectra of are multiplied by 10⁴ for clarity. The shaded grey areas of the left and centre panels denote the region between z = −200 km and z = 0 km, used for the spatial average of the energy spectra.