New evidence for geomagnetically trapped anomalous cosmic rays

We report new observations of ≥ 15 MeV/nuc trapped heavy ions with Z ≥ 2, made on the polar-orbiting SAMPEX spacecraft in late 1992 and early 1993. A trapped population that includes He, N, O, and Ne is found to be located at L ≈ 2. We conclude that the observed N, O, and Ne ions are "anomalous" cosmic rays, trapped by the mechanism proposed by Blake and Friesen. While it is not expected that this mechanism would also trap anomalous He, the characteristics of the trapped He population are generally consistent with those of N, O, and Ne.