Green’s functions for the auroral zones surface area (top) and centroid latitude (bottom) with respect to changes of the radial magnetic field, B_c at the core-mantle boundary (CMB). The panels on, respectively, the left (right) refers to the northern (southern) zone. The shape of the auroral zone under consideration (northern or southern) is indicated via the red dashed lines while the location of the centroid is shown in the maps via a red square.