Decreases in the flux of energetic (>30 keV9 electrons and protons followed by very rapid increases are characteristics of the magnetospheric subtorms observed on ATS 6 at synchronous orbit in the region about midnight. By using proton gradient information from the University of Minnesota electron-proton spectrometer the decreases are interpreted as a physical motion of the trapped particle outer boundary from the satellite toward a region equatorward and earthward of the satellite. The particle recoveries are found to be associated with an expansion phase onset of a magnetospheric substorm. The motion corresponding to these flux increases may be organized into three types according to the direction of the gradient. In the most common type of recovery the flux increase is observed first on guiding centers north and tailward of the spacecraft and represents motion, presumably of the plasma sheet, from north and tailward to south and earthward of ATS 6. This motion is observed most frequently near local midnight. Recoveries are also observed over a broad local time range on the nightside, in which the indicated motion is from earthward and equatorward of the satellite to a region above and tailward. For other particle increases observed in the evening sector a recovery associated with motion frmo beneath the satellite to above the satellite frequently is followed by a second increase enveloping the satellite from north and tailward.