Fig 1. Time series evolution.

Evolution of a) the SAA area extent (within the 32000 nT isoline of the geomagnetic field) on the Earth’s surface in km² from three global geomagnetic field models [27, 35, 36] and b) GSL rise in mm, for the last 300 years (1700–2000). The lines represent the fits by using penalized cubic splines: (red, green, blue) SAA derived from Jackson et al. [35], Gubbins et al. [27] and Finlay [36], respectively, and (gray) GSL.