MAGSAT data revealed the following characteristics of geomagnetic perturbations at high latitudes: Parallels (ΔB⊥) and transverse (ΔB⊥, especially geomagnetic east-west component) magnetic perturbations represent respectively scalar potential field (due primarily to electric currents within the ionosphere) and vector potential field (attributable to field-aligned currents and associated ionospheric currents). The spatial gradient of ΔB∥ is shown to be very useful to infer the ionospheric current distribution. The ratio of ΔB∥ and ΔB⊥ depends on the height of satellite measurement and also on the electric conductivity of the ionosphere.