Data from energetic ion mass spectrometers on the ISEE 1 and AMPTE/CCE spacecraft are combined with geomagnetic and solar indices to investigate, in a statistical fashion, whether energized O+ ions of terrestrial origin constitute a source of feedback which triggers or amplifies geomagnetic activity, as has been suggested in the literature, by contributing a destabilizng mass increase in the magnetotail current sheet. The ISEE 1 data (0.1--16 keV/e) provide in situ observations of the O+ concentration in the central plasma sheet, inside of 23 RE, during the rising and maximum phases of solar cycle 21, as well as inner magnetosphere data from same period. The CCE data (0.1--17 keV/e), taken during the subsequent solar minimum, all within 9 RE, provide a reference for long-term variations in the magnetosphere O+ content. Statistical correlations between the ion data and the indices, and between different indices, all point in the same direction: there is probably no feedback specific to the O+ ions, in spite of the fact that the often contribute most of the ion mass density in the tail current sheet. ¿ American Geophysical Union 1993