Figure 4: The Levantine geomagnetic spike.
Contours of field intensity, F (μT), at Earth’s surface (r=a) from the CHAOS-4 model2 at 2010 (a) the CALS10k.2 global field model at 1000 BC (b) and CALS10k.2 at 1000 BC plus a superposed best-fitting spike at 20° N, 40° E with amplitude A=400 mT and s.d. of σ=1° at the CMB (c). Symbols show paleointensities for samples dated at 1150–1050 BC (triangles), 1049–950 BC (squares) and 949–850 BC (circles). Symbol colours are blue (40–50 μT), green (51–60 μT), yellow (61–70 μT), orange (71–90 μT), red (91–115 μT) and black (>115 μT). White triangles in a–c mark the north pole of the dipole field. (d) Longitudinal cross-section through the spike in c, at Earth’s surface (blue, right ordinate) and the CMB (r=c, red, left ordinate). The horizontal dashed line marks the width at half maximum δ2(a). Available data within 20°±15° N are shown corrected to 20° N using the formula for an axial dipole field, 
, where θ is colatitude. Error bars correspond to the uncertainties in Fig. 3b. Open and closed symbols cannot be simultaneously matched by the model.
