Is the AE index a valid indicator of solar wind power input during northward IMF?

The fact that the auroral electrojet (AE) index is typically strongly enhanced during times of southward interplanetary magnetic field (IMF) is a major reason why a southward IMF is popularly thought to be a necessary, or at least favorable, condition for the transfer of solar wind power (and mass) across the magnetopause. Attempts to verify this by comparing variations in the IMF and the solar wind power input with subsequent concentration of energetic (keV) magnetospheric O + ions of terrestrial origin have failed, however (Lennartsson, 1995), casting doubt on this interpretation of the AE. As a follow-up, it is argued here, by employing simple modeling of the electrojets, that the principal difference between northward and southward IMF in the presently-produced AE can instead be accounted for by the different spatial relationships between the currents and the AE ground stations.