Ionospheric currents estimated simultaneously from CHAMP satelliteand IMAGE ground-based magnetic field measurements: a statisticalstudy at auroral latitudes P. Ritter, H. Lühr, A. Viljanen, O. Amm, A. Pulkkinen, I. Sillanpää
Annales Geophysicae, Vol. 22, pp 417-430, 1-1-2004