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Table 1 Selection criteria for satellite (Champ and Swarm) and ground observatory data

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

Mag. latitude \(|\text{mag}. \; \text{lat}.| \ge 55^\circ\) \(|\text{mag}. \; \text{lat}.| \le 55^\circ\)
Data type Swarm Champ Obs. Swarm Champ Obs.
Time sampling \({60}\,{\mathrm{s}}\) \({60}\,{\mathrm{s}}\) \({1}\,{\mathrm{h}}\) \({30}\,{\mathrm{s}}\) \({20}\,{\mathrm{s}}\) \({1}\,{\mathrm{h}}\)
Local time 23:00–5:00 23:00–5:00 23:00–5:00
\(\mathrm {D}_{\text{st}}\) \([-30: 30]{}\,{\mathrm{nT}}\) \([-30: 30]{}\,{\mathrm{nT}}\) \([-30: 10]{}\,\,{\mathrm{nT}}\) \([-30: 30]{}\,{\mathrm{nT}}\) \([-30: 30]{}\,{\mathrm{nT}}\) \([-30: 10]{}\,{\mathrm{nT}}\)
IMF \(B^{\mathrm {IMF}}_z> 0\) \(B^{\mathrm {IMF}}_z> 0\) \(B^{\mathrm {IMF}}_z> 0\) \(B^{\mathrm {IMF}}_z> 0\) \(B^{\mathrm {IMF}}_z> 0\) \(B^{\mathrm {IMF}}_z> 0\)
Sunlit area excl. No No Yes Yes Yes Yes
\(N_{\mathrm {v}}\) 1,104,672 637,561 906,513 822,246 1,004,634 1,646,564