The Kalmag model as a candidate for IGRF-13

Earth, Planets and Space

Table 1 Magnetic sources considered in the model

Source	Coordinate	\(\ell_{\text{max}}\)	SH decomposition
Core \(g_{\text{c}}\)	GEO	20	Standard
Lithospheric \(g_{\text{l}}\)	GEO	76	Standard
Remote magnetospheric \(g_{\text{rm}}\)	GSM	1	Zonal
Close magnetospheric \(g_{\text{m}}\)	SM	15	Zonal
Fluctuating magnetospheric \(g_{\text{fm}}\)	SM	15	Zonal iso
Residual ionospheric/ induced \(g_{\text{ii}}\)	MAG	50	Zonal iso
Field-aligned currents \(g_{\text{fac}}\)	SM	15	Zonal iso

The second column corresponds to the coordinate system each field is expressed in. GEO stands for geographic, SM for solar magnetic, MAG for magnetic and GSM for geocentric solar magnetospheric. \(\ell_{\text{max}}\) is the maximum degree of the SH expansion, for the three following types of decomposition: standard with \(m=[-l,l]\), zonal with \(m=0\) and zonal iso where \(m=\{0,1,-1\}\)