On August 13, 1974, a few hours after local midnight, the ATS 6 NOAA insturment in geostationary orbit observed oscillations in the fluxes of ions from 24 keV to 150 keV (five channels) that had three striking characteristics: First, the starting times of the oscillations were observed to be different in different energy channels. The modulation was observed initially in the high-energy channel and progressively later in the lower energy channels. Second, the oscillation frequency was higher for the highest energy ions and decreased with the ion energy; the multiple frequencies appeared to be discrete and harmonically related. Third, the duration of oscillations were energy dependent; the higher the ion energy, the shorter the duration of the oscillation in that channel. We conclude that the flux modulations did not start in the region where they were observed but were actually the preserved signatures drifting in longitude of flux modulations resulting from wave-particle resonant interactions that occurred at an eariler time in a region east of ATS 6 probably associated with the onset of a substorm. Although flux oscillations of this kind are seldom observed, the drifting ions are apparently capable of preserving the signatures of the flux modulation after they leave the interaction region. The interaction region has been found to cover a wide magnetospheric local time sector from near midnight through the noon meridian, to the late morning hours.