The mean models considered are the arithmetic mean model M, the model MnoD which is an arithmetic mean excluding candidate D, and the model MABG that is an arithmetic mean model derived only from candidates A, B and G.
Right plot shows the SH degree correlation i,M ρ n (Eq. 11) of DGRF-2010 candidate models with the arithmetic mean model M. A final analysis is provided by the differences between the candidate models and the simple arithmetic mean model M in space.
Hence, the log-based arithmetic model that has to append with B9/7 DWT structure is slightly altered to suit the IEEE754 standard as shown in Figure 7.
Some of the strongly down-weighted features correlate well with the spatial differences between the candidate models and the arithmetic mean model (Fig. 4).
Lowes-Mauersberger power spectra i,0R n from (3) of IGRF-2010 candidate models at radius 3480 km (core-mantle boundary) (left) and degree correlation i,M ρ n (9) of IGRF-2010 candidate models with the arithmetic mean model M (right).
Figure 1 (right) presents the degree correlation i,M ρ n as defined in (9) between the DGRF-2005 candidate models and the arithmetic mean model M. Candidate D displays a low degree correlation to M above degree 9.
The spherical degree correlation i,M ρ n as defined in Eq. 11 between the DGRF-2010 candidate models and the arithmetic mean model M is shown in Fig. 2-right.
Right plot shows the SH degree correlation i,M ρ n (Eq. 11) of IGRF-2015 candidate models with the arithmetic mean model M. The Fig. 6 compares the sensitivity matrix S n,m) as defined by Eq. 10 of the difference between candidate model B and the mean model M (left) and also between the candidate model J and the mean model M (right).
Fig. 7. Left plot shows differences as defined in (1) between IGRF-2010 candidate models and the arithmetic mean Model M as a function of the index of the spherical harmonic coefficient (running from etc indexed 1, 2, 3, 4, 5, etc).
Right plot shows the SH degree correlation i,M ρ n (Eq. 11) of SV-2015-2020 candidate models with the arithmetic mean model M Fig. 10 Difference in nT/yr in the radial B r component of the magnetic field between each SV-2015-2020 candidate model (labeled with capital letter, see Table 6 for details) and the mean model M plotted at Earth's reference radius in Mollweide projection.
