Fig. 8

Spectral RMS misfit between IGRF-13 and the 9 IGRF-12 SV candidate models for 2015.0–2020.0. Dashed lines represent coefficient differences to SH degree 8, dotted lines to SH degree 13 (with SV candidates zero-padded). “Spline” refers to an updated version of the BGS parent model built with data through February 2020. Those models labelled with bold text used physics based predictions, the remaining used mathematical predictions