Geomagnetically trapped light isotopes observed with the detector NINA

[1] The detector New Instrument for Nuclear Analysis (NINA) aboard the satellite Resurs-01-N4 detected hydrogen and helium isotopes geomagnetically trapped, while crossing the South Atlantic Anomaly. Deuterium and tritium at L shell < 1.2 were unambiguously recognized. The He-3 and He-4 power law spectra, reconstructed at L shell = 1.2 and B < 0.22 G, have indices equal to 2.30 +/- 0.08 in the energy range 12-50 MeV nucleon 1 and 3.4 +/- 0.2 in 10-30 MeV nucleon(-1), respectively. The measured He-3/He-4 ratio and the reconstructed deuterium profile as a function of L shell bring one to the conclusion that the main source of radiation belt light isotopes at Resurs altitudes (similar to800 km) and for energy greater than 10 MeV nucleon(-1) is the interaction of trapped protons with residual atmospheric helium.