It is possible to calculate, with the Magsat data, the total amount of electric current passing through the plane enclosed by the Magsat orbit, from the line integration of the observed magnetic field component tangential to the Magsat orbit, i.e., a direct application of Amp¿re's theorem. After eliminating the spurious effect arising from the earth's rotation under the Magsat orbit, it is concluded that the space current of a few million amp. flows antisunward below the Magsat level during magnetic storms, whereas such a space current is almost absent on quiet condition. The depression in the horizontal intensity of geomagnetic field in low latitudes is noticeably greater on the duskside than on the dawnside, especially at the developing stages of magnetic storms. Combining these two observations, we may conclude that 10--20% of the westward ring (or shell) current in the dusk magnetosphere will close its current circuit with antisunward field-aligned current in the magnetosphere connected with a net horizontal current flowing in the ionosphere.