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Table 1 Summary of data selection criteria for Swarm and ground observatory data

From: The BGS candidate models for IGRF-13 with a retrospective analysis of IGRF-12 secular variation forecasts

Filter Description Satellite Observatory
Sampling Every 20th datum Hourly mean
Kp, Kp\(_\text {-3h}\) 3 h planetary K index at datum and in preceding 3 h interval ≤ 20, ≤ 20 \(\le \; \) 2\(_\text {+}\), –
|Dst| [nT], |dDst/dt| [nT h\(^{-1}\)] Storm time disturbance and its rate of change per hour at datum ≤ 30, ≤ 2 –, \(\le \; \) 5
IMF B\(_\text {x}\), B\(_\text {y}\), B\(_\text {z}\) [nT] Projected interplanetary magnetic field at datum \(\le |\) 10|, \(\le |\)3|, 0 \(\le \; \)× \(\le \; \) 6 –, –, \(\ge\) − 2
v\(_\text {sw}\) [km s\(^{-1}\)] Projected solar wind velocity at datum \(\le \; \) 450
LT (\(<|\)55\(^\circ \)GMD|) Local time at GMD latitudes below |55\(^\circ \)| 23:00 \(\le \; \) x \(\le \; \) 05:00 01:00 \(\le \; \) x \(\le \; \) 02:00
|d−m\(_\text {prior}\)| [nT] Absolute difference between datum and a preliminary version of our parent model \(\le \; \)100
|F–|B|| [nT] Absolute difference between ASM and magnitude of VFM data \(\le \; \)2
E\( {m}\) (\(\ge \) |55\(^\circ \)GMD|) [mV m\(^{-1}\)] Hourly mean of 1 minute merging electric field, calculated as in Newell et al. (2007) \(\le \; \)0.8