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Table 1 CM6 parameterization

From: CM6: a comprehensive geomagnetic field model derived from both CHAMP and Swarm satellite observations

Field source/effect# ParmsDescription
Core/lithosphere30, 480SpatialGeographic spherical harmonic (SH) \(N_{\text{max}} = 120\)
TemporalOrder 4 B-splines SV, 6-month knot spacing from \(1999.0-2019.5\), epoch 2015.0, up to \(N_{\text{max}} = 18\)
\(M_2\) tidal2, 736SpatialGeographic SH \(N_{\text{max}} = 36\)
TemporalPeriod of 12.42060122 h, Greenwich fixed phase, complex coefficients
\(N_2\) tidal2, 736SpatialGeographic SH \(N_{\text{max}} = 36\)
TemporalPeriod of 12.65834751 h, Greenwich fixed phase, complex coefficients
\(O_1\) tidal2, 736SpatialGeographic SH \(N_{\text{max}} = 36\)
TemporalPeriod of 25.81933871 h, Greenwich fixed phase, complex coefficients
Ionosphere/induced5, 520SpatialQuasi-dipole (QD) frame, underlying dipole SH \(N_{\text{max}} = 60\), \(M_{\text{max}} = 12\)
TemporalAnnual, semi-annual, 24, 12, 8, and 6 h periodicities with \(F_{10.7}\) scaling plus induction via a priori 3D conductivity model (“1D+oceans”) and infinite conductor at depth
Magnetosphere/induced685, 110MagnetosphereSpatial:dipole SH \(N_{\text{max}} = 1\)
Temporal:Discretized in 1-h bins
InducedSpatial:dipole SH \(N_{\text{max}} = 1\)
Temporal:Discretized in 1-h bins
OHM biases597One vector bias for each station in local spherical system
VFM-CRF alignment4, 755Three XYZ-type Euler angles every 10 days for each Swarm satellite and CHAMP satellite single- and double-headed star trackers
Total734, 670