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Table 3 Summary of all modelled sources with relevant parameters and prior information values

From: Sequential modelling of the Earth’s core magnetic field

Source \(L_i\), \(L_a\) Time scale Prior Nb. of par. Coef.
Static core field 1, 18 \({\tilde{\tau }}_{\ell }^c = 415/\ell \; \text {year}\) \({\begin{array}{l} R = {3000}\,{\mathrm{km}} \\ S = {2\cdot 10^9}\,\mathrm {nT^2} \end{array}}\) 360 \({}^{\mathrm {C}}{g}_{\ell }^m\)
Core SV 1, 18 \({\tilde{\tau }}_\ell ^{sv} = {11}\,{\mathrm{year}}\) \({\begin{array}{l} R = {3500}\,{\mathrm{km}} \\ S = {1.5\cdot 10^4}\,\mathrm {(nT/year)^2} \end{array}}\) 360 \({}^{\mathrm {C}}{\dot{g}}_{\ell }^m\)
Lithospheric field 15, 30 \(\tau ^{lt} = {10^6}\,{\mathrm{year}}\) \({\begin{array}{l} R = {6280}\,{\mathrm{km}} \\ S = {2.7\cdot 10^{-2}}\,\mathrm {nT^2} \end{array}}\) 736 \({}^{\mathrm {L}}{g}_{\ell }^m\)
Induced field 1, 6 \(\tau ^{I} < \Delta t\) 48 \({}^{\mathrm {I}}{g}_{\ell }^m\)
Induced field variation 1, 6 \(\tau ^{\partial _t I} < \Delta t\) 48 \({}^{\mathrm {I}}{\dot{g}_{\ell }^m}\)
GSM ext. field 1, 3 \(\tau ^{\text {GSM}} < \Delta t\) \({\begin{array}{c} R = 1.6 \cdot 10^4 \, \mathrm {km} \\ S = {5.4\cdot 10^3}\,\mathrm {nT^2} \end{array}}\) 15 \({}^{{\mathrm {G}}}{q_\ell ^m}\)
SM ext. field 1, 3 \(\tau ^{\text{SM}} < \Delta t\) \({\begin{array}{l} R = {6900}\,{\mathrm{km}} \\ S = {3.56}\, \mathrm {nT^2} \end{array}}\) 15 \({}^{{\mathrm {S}}}{q_\ell ^m}\)
\(\mathrm {I}_{\text{st}}\) indexed field 1, 3 \(\tau ^{\text{Ist}} < \Delta t\) \({\begin{array}{l} R = {2537}\,{\mathrm{km}} \\ S = 1.0 \end{array}}\) 15 \({}^{{\mathrm {I_{\text{st}}}}}{g_\ell ^m}\)
\(\mathrm {E}_{\text{st}}\) indexed field 1, 3 \(\tau ^{\text{Est}} < \Delta t\) \({\begin{array}{l} R = 1.6 \cdot 10^4 \, \mathrm {km} \\ S = {5.4} \end{array}}\) 15 \({}^{{\mathrm {E_{\text{st}}}}}{q_\ell ^m}\)
\(B^{\mathrm {IMF}}_y\) indexed field 1, 3 \(\tau ^{\text{IMF} }< \Delta t\) \({\begin{array}{l} R = {6900}\,{\mathrm{km}} \\ S = {0.1} \end{array}}\) 15 \({}^{{\mathrm {I}}}{q_\ell ^m}\)
Obs. offset Non SH \(\tau ^{lt} = {10^6}\,{\mathrm{year}}\) \(3 \times 200\) \({{\mathbf {O}}}_i\)
  1. From left to right: name of the source, minimum (\(L_i\)) and maximum (\(L_a\)) harmonic degrees (when relevant), time scale, radius and scale for the HS prior (see “Analysis step” section), total number of parameters, and coefficient notation used in Eq. (1). \(\Delta t\) is set to 3 months in this study. No R and S values are given for the induced field and its variation. See “Analysis step” section for the construction of the statistics for these latter contributions