Geomagnetic core field models and secular variation forecasts for the 13th International Geomagnetic Reference Field (IGRF-13)

Wardinski, I.; Saturnino, D.; Amit, H.; Chambodut, A.; Langlais, B.; Mandea, M.; Thébault, E.

doi:10.1186/s40623-020-01254-7

Earth, Planets and Space

Table 3 Specification of damping parameters of the frozen-flux field model based on the tangential geostrophic flow assumption, except model x0a, which is based on a purely toroidal flow assumption

From: Geomagnetic core field models and secular variation forecasts for the 13th International Geomagnetic Reference Field (IGRF-13)

	\(\lambda _s\)	\(\lambda _T\)	\(\lambda _{TG}\)	\(\lambda _{E}\)	\({\mathsf{S/T}}\)	\({\mathsf{R}}\)	M
x0a	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	–	\(1\times 10^{2}\)	0/1	0.957\(\times 10^{-3}\)	2.1184
x3a	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{3}\)	\(1\times 10^{2}\)	0/1	\(0.791\times 10^{-3}\)	2.1196
x3b	\(1\times 10^{-3}\)	\(1\times 10^{-5}\)	\(1\times 10^{3}\)	\(1\times 10^{2}\)	0/1	\(0.941\times 10^{-3}\)	2.1185
x3c	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{4}\)	\(1\times 10^{2}\)	0/1	\(0.123\times 10^{-2}\)	2.1233
x3d	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{5}\)	\(1\times 10^{2}\)	0/1	\(0.102\times 10^{-2}\)	2.1237
x3e	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{6}\)	\(1\times 10^{2}\)	0/1	\(0.166\times 10^{-3}\)	2.1431
x3f	\(1\times 10^{-3}\)	\(1\times 10^{-3}\)	\(1\times 10^{4}\)	\(1\times 10^{2}\)	0/1	\(0.774\times 10^{-3}\)	2.1322
x3g	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{10}\)	\(1\times 10^{2}\)	0/1	\(0.136\times 10^{-2}\)	2.1627
x3g1^†	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{10}\)	\(1\times 10^{2}\)	0/1	\(0.431\times 10^{-3}\)	2.1856
x3h	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{12}\)	\(1\times 10^{2}\)	0/1	\(0.106\times 10^{-2}\)	2.1632
x3j	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{8}\)	\(1\times 10^{2}\)	0/0	\(0.311\times 10^{-2}\)	2.1695
x3k	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{7}\)	\(1\times 10^{2}\)	0/0	\(0.696\times 10^{-2}\)	2.1634
x3k1^†	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{7}\)	\(1\times 10^{2}\)	0/0	\(0.332\times 10^{-2}\)	2.2221
x3l	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{6}\)	\(1\times 10^{2}\)	0/0	\(0.129\times 10^{-1}\)	2.1525
x3m	\(1\times 10^{-3}\)	\(1\times 10^{-4}\)	\(1\times 10^{4}\)	\(1\times 10^{2}\)	0/0	\(0.524\times 10^{-3}\)	2.1396

The parameter controlling the frozen-flux constraint is kept fixed, i.e. \(\lambda _1=1\times 10^{-9}\) for most of the inversions, except those marked with^†, there we set \(\lambda _1=1\times 10^{-7}\). In all inversions, the parameter controlling the flow acceleration at model end points is set to \(\lambda _4=1\times 10^{2}\). \({\mathsf{S/T}}\) identifies which temporal derivative of the spatial and temporal norm is applied, respectively (see text). \({\mathsf{R}}\) and \({\mathsf{M}}\) are defined by (26) and (25), respectively. \({\mathsf{M}}\) is given in \(\text{nT/year}\). The model x0a represents a field model with purely toroidal flow

Back to article page