The motion of ionospheric ions in the magnetospheric tail is considered using a minimal set of well-known factors, such as the tail-like configuration of the magnetic field and the presence of the dawn-to-dusk magnetospheric electric field. The calculated O+ ion density and average energy are in close agreement with satellite measurements. An abrupt increase of the magnetospheric electric field leads to formation of a hot plasma cloud in the plasma sheet, which convects earthward. In contrast, if the electric field varies slowly in time, then the mean energy of ionospheric ions in the near-Earth tail remains almost independent of activity level. ¿ American Geophysical Union 1996