Recent measurements of the ion composition in the magnetospheric boundary layer indicate that the boundary layer may contain clouds of magnetosheath plasma which are gradually becoming mixed with the magnetospheric plasma. A significant difference between flow vectors of different ion species (≈50--100 km/s) implies that an ideal MHD equation E+V¿B=0, does not fully describe the macroscopic plasma flow inside such inhomogeneities. An analysis based on the first-order drift theory indicates that gradients of the partial ion pressure and of the magnetic field could induce differential ion drifts comparable in magnitude to the electric drift velocity. We discuss some implications of these results on the physics of solar wind-magnetosphere interactions. ¿American Geophysical Union 1987