Fig. 6
From: Physics-based secular variation candidate models for the IGRF
Direction error at Earth’s surface for past IGRF SV models (blue) and IGRF-11 and IGRF-12 candidate models (in grey). a Root-mean-squared error. b Maximum error at mid-latitude ML (absolute value geographic latitude smaller than \(60^\circ\)). See text for the definition of the pointwise error. Magnetic fields are expanded up to spherical harmonic degree and order 8