  The composition of ions plays a crucial role for the fundamental plasma
properties in the terrestrial magnetosphere. We investigate the
oxygen-to-hydrogen ratio in the near-Earth magnetosphere from -10 RE<XGSE}< 10
RE. The results are based on seven years of ion flux measurements in the energy
range ~10 keV to ~955 keV from the RAPID and CIS instruments on board the
Cluster satellites. We find that (1) hydrogen ions at ~10 keV show only a
slight correlation with the geomagnetic conditions and interplanetary magnetic
field changes. They are best correlated with the solar wind dynamic pressure
and density, which is an expected effect of the magnetospheric compression; (2)
~10 keV O+ ion intensities are more strongly affected during disturbed phase of
a geomagnetic storm or substorm than >274 keV O+ ion intensities, relative to
the corresponding hydrogen intensities; (3) In contrast to ~10 keV ions, the
>274 keV O+ ions show the strongest acceleration during growth phase and not
during the expansion phase itself. This suggests a connection between the
energy input to the magnetosphere and the effective energization of energetic
ions during growth phase; (4) The ratio between quiet and disturbed times for
the intensities of ion ionospheric outflow is similar to those observed in the
near-Earth magnetosphere at >274 keV. Therefore, the increase of the energetic
ion intensity during disturbed time is more likely due to the intensification
than to the more effective acceleration of the ionospheric source. In
conclusion, the energization process in the near-Earth magnetosphere is mass
dependent and it is more effective for the heavier ions.
