Fig. 1
From: Solar superstorm of AD 774 recorded subannually by Arctic tree rings

Map of the study region. The colour codes show the latitudinal differences of 14C production rate (14C cm−2) for a typical strong SPE (such as 23 February 1956, the strongest directly observed event, Supplementary Table 2). The 14C production model36 is described in the Methods section. The red full circles with three-letter coding show the measurement locations for 14C intensities (see text). The cross illustrates the location of the Geomagnetic North Pole in AD 775