Ions Abundance Close to the Earth Surface:. the Role of the Magnetosphere

We have compared the data of protons and helium from the AMS-01 detector in the energy range 0.1-200 GeV, and heavier ions (from Z=4 to Z=28) from the HEAO-3-C2 in the energy range 0.6-35 GeV/n. Data have been collected almost in the same solar period and the same polarity (1980 for HEAO and 1998 for AMS-01). The experimental conditions are also comparable: altitude and inclination of the orbit, angular acceptance of the detectors. The effect of magnetosphere is to introduce a rigidity cut-off. The results are that the abundance ratio of nuclei/protons is larger than what expected from the spectra measured outside the magnetosphere. We discuss this effect in relation to what has been observed in experiments on board of satellites orbiting near the Earth surface.