Comparison of calibration curves in a more detailed way than in Fig. 5. When the kernels are interpolated onto the MURaM grid, the results do not substantially change (dotted curves), except at ℓ ≈ 20. The crosses and plusses indicate the grid points in harmonic degree, which were obtained by converting horizontal Fourier modes from Cartesian into spherical geometry (see Appendix A.4). The kernels were computed on a spatial grid with a four times larger spatial extent than the MURaM grid, therefore the resolution in Fourier space, , is four times finer.