Table 1 Comparison of the CHAOS-4 and CHAOS-5 geomagnetic field models
From: DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model
CHAOS-4 | CHAOS-5 | |
|---|---|---|
Data sources | ||
Observatory monthly means | June 1997 - June 2013 | June 1997 - Sept 2014 |
Ørsted vector | March 1999 - Dec 2004 | March 1999 - Dec 2004 |
Ørsted scalar | March 1999 - June 2013 | March 1999 - June 2013 |
SAC-C scalar | Jan 2001 - Dec 2004 | Jan 2001 - Dec 2004 |
CHAMP vector and scalar | Aug 2000 - Sept 2010 | Aug 2000 - Sept 2010 |
Swarm A vector and scalar | – | Nov 2013 - Sept 2014 |
Swarm B vector and scalar | – | Nov 2013 - Sept 2014 |
Swarm C vector and scalar | – | Nov 2013 - Sept 2014 |
Time-dependent internal field | ||
Model time span | 1997.0–2013.5 | 1997.0–2015.0 |
Spherical harmonic degree | n=1–20 | n=1–20 |
Spline basis | 6th order, 0.5 year knots | 6th order, 0.5 year knots |
Based on | CHAOS-4l | CHAOS-5l |
Static internal field | ||
Spherical harmonic degree | n=21–90 | n=21–90 |
Based on | CHAOS-4l (n=21–24) | CHAOS-5l (n=21–24) |
and CHAOS-4h (n=25–90) | and CHAOS-4h (n=25–90) | |
External field | ||
SM | n=1: 1 h, RC int + ext | n=1: 1 h, RC int + ext |
5 day \(\Delta {q^{0}_{1}}\), 30 day \(\Delta {q^{1}_{1}}\), \(\Delta {s^{1}_{1}}\) | 5 day \(\Delta {q^{0}_{1}}\), 30 day \(\Delta {q^{1}_{1}}\), \(\Delta {s^{1}_{1}}\) | |
n=2: static | n=2: static | |
GSM | n=1–2, m=0: static | n=1–2, m=0: static |
Euler angles | ||
Ørsted | Before and after Jan 24 2000 | Before and after Jan 24 2000 |
CHAMP | 10 day bins | 10 day bins |
Swarm | – | 10 day bins |
Regularization | ||
Spatial | Static field n>85, \(<{B_{r}^{2}}>\) | Static field n>85, \(<{B_{r}^{2}}>\) |
λ 0=1 nT−2 | λ 0=1 nT−2 | |
Temporal, interior | \(<(d{B^{3}_{r}}/dt^{3})^{2}>\) | \(<(d{B^{3}_{r}}/dt^{3})^{2}>\) |
λ 3=0.33 (nT/year−3)−2 | λ 3=0.33 (nT/year−3)−2 | |
except \({g^{0}_{1}}\), λ 3=10 (nT/year−3)−2 | except m=0, λ 3=100 (nT/year −3)−2 | |
Temporal, endpoints | \(<(d{B^{2}_{r}}/dt^{2})^{2}>\) | \(<(d{B^{2}_{r}}/dt^{2})^{2}>\) |
λ 2=10 (nT/year−2)−2 | λ 2=100 (nT/year −2)−2 |