Energetic neutral atoms (ENA), emitted from the magnetosphere with energies of ~50 keV, have been measured with solid-state detectors on the IMP 7/8 and ISEE 1 spacecraft. The ENA are produced when singly charged trapped ions collide with the exospheric neutral hydrogen geocorona and the energetic ions are neutralized by charge exchange. ENA observations during the recovery phase of two moderate geomagnetic storms are analyzed in detail: November 22--23, 1973, from IMP 8 at 33 RE, and December 17, 1977, from ISEE at 20 RE. The three-dimensional viewing capability of the Medium Energy Particle Instrument (MEPI) on ISEE 1 provides coarse spatial information; i.e., the ENA emission fell off significantly beyond L≂5 in the midnight and morning sectors of magnetic local time. The spectral resolution of the MEPI allowed us to deduce that oxygen atoms dominated the ENA fluxes at energies of ~100 keV because the decay time constant (7.5 hours) for the ENA fluxes was identical in the two lowest energy channels over 10 hours. Combining the spatial and spectral information from ISEE 1, we estimate an ENA unidirectional differential flux JO≂30 (cm2 s sr keV)-1 for 100-keV oxygen atoms with an e-folding energy of 20 keV at the beginning of the recovery phase. This ENA flux implies a singly charged oxygen ion flux jO+≂3.5¿104 (cm2 s s keV)-1 near the inner edge of the ring current region, and we estimate a corresponding decay time for geocorona H atoms ≂9 days at that time and location. Using a newly derived relation between the recovery rate of the ring current disturbance (dDst/dt) and the measured ENA flux, we show self-consistently that charge-exchange loss of O+ ions was the dominant mechanism in the recovery of DSt in both of the storms observed in ENA by IMP 8 and ISEE 1. Even though oxygen dominated the ENA flux and the ring current energy loss rate at ~100 keV, H+ intensities at these energies could still have been comparable to those of O+ in the ring current (because the charge-exchange cross section for H+ is much smaller than that for O+ at 100 keV).