Height dependence of the power-law indices of the vertical velocity power spectra throughout almost the entire height range of the simulation box (the top and bottom parts, which may be affected by the boundary conditions, are not covered). A height of 0 km indicates the location of the solar surface (τ₅₀₀₀ = 1). The horizontal line marks the Kolmogorov value of −5/3. The length of the vertical error bars represents the ± uncertainties of the least-squares fit to determine the power-law indices at each height in the numerical grid.