Fig. 6

Lithospheric field at the Earth’s surface expanded up to spherical harmonics degree \(\ell =150\). Left: mean downward component solution for the FR model estimated with full covariance information (top) and for the PR model estimated with variance only information from \(\ell =30\) (bottom). Top right: difference between FR and PR models mean downward components. Bottom right: energy spectra of the means (solid lines), the standard deviations (dashed lines) and the difference (crosses) between the FR model (black lines) and PR model (blue lines)