The ratio of positron=electron uxes originating in nuclear reactions in the Earth's Magnetosphere is considered. It is supposed that positrons as well as electrons are mainly produced in the decay of charged pions Β± β Β± β e Β± born in nuclear collisions of trapped relativistic inner zone protons and of cosmic rays with the residual atmosphere. These positrons and electrons are captured in the magnetosphere and create a positron and electron radiation belt of nuclear origin. The positron=electron trapped magnetospheric uxes formed with this mechanism from radiation belt proton source are simulated and the resulting computed e + =e -ux ratio β 4 appears to be in agreement with the recent observations made by the Alpha Magnetic Spectrometer (AMS) (The AMS collaboration, 1999). A ΒΏ 200 MeV positron ux with an intensity about 4 times higher than the electron ux of the same energy was registered in the equatorial region at the altitude of β 400 km. This ratio is signiΓΏcantly di erent from the computed ratio β 1 obtained from the primary cosmic ray source through the same mechanism. As our modeling of nuclear spallation reaction shows, in the same reaction nuclei of isotopes of hydrogen and helium are also produced, which are the source of light element isotope radiation belts of D, T, 3 He and 4 He with a signiΓΏcant excess of 3 He over 4 He uxes. The AMS instrument, as we have known, also looked at the distribution of helium nuclei and only 3 He was observed, which is one more evidence in favor of the above hypothesis.