Spectra of the radial kinetic energy component. The blue and orange line correspond to simulations with the Roe and schemes of a reduced domain that only contains a fraction of the convection zone. The gray line shows the spectrum for a simulation of the full domain with the solver, the same grid spacing, but a different energy boosting. The amplitudes have been normalized such that they are unity at ℓ = 200 to ease the comparison. The dashed line marks the Kolmogorov-scaling according to Eq. (13). The vertical dotted line at ℓ_max = 60 denotes the spectral width of the applied window functions for the runs with 270 × 180² cells. For ℓ ≤ ℓ_max, their spectra are dominated by the convolution with the window function and do not reflect real data. The horizontal axis is truncated at the spectral width of the window function for the 540 × 360² run which corresponds to ℓ_max = 25.