Fig. 3.

Optimized flow geometries and their SVs. (A–D) The flow structure on the CMB (arrows) overlaid by contours of the radial SV Ḃ_r. (E–H) The corresponding rate of intensity change Ḟ on Earth’s surface. These optimal solutions are calculated from the radial magnetic field at the CMB (I) and Ḟ on Earth’s surface (J), according to the CALS10k.2 model, in 1590 AD. On the Earth’s surface, the center point of the WPA and the location of the auroral observations in Korea are marked as white stars and diamonds in E–H and J; projections of these locations onto the CMB are shown by black stars and diamonds in A–D and I.