Fig. 4: Estimates of axial dipole dominance for the ancient geomagnetic field.
From: Quantitative estimates of average geomagnetic axial dipole dominance in deep geological time
a Application of the power law in Fig. 2 to ascertain the first quantitative estimates of axial dipole dominance in deep time (see Table 1). Horizontal range of boxes indicates nominal time range; vertical range indicates 95% uncertainties with numerical bounds provided. Crosses relate to age of one or more rock units comprising the estimate within the box. Reversal frequency was calculated using 10 Myr bins38. b Relationship between palaeosecular variation and time-averaged inclination anomaly in outputs of dynamo models (blue circles). Shaded area represents 95% confidence bounds. Dataset from the last 10 Myr19 (purple square) is shown to fit the linear trend well. Extrapolations of inclination anomalies (ΔInc) are made using median a parameters for four earlier datasets shown in panel a.
