SAMPEX Observations of Geomagnetically Trapped Anomalous Cosmic Rays

Abstract

We summarize observations of trapped anomalous cosmic rays made with the Mass Spectrometer Telescope (MASn on the polar-orbiting SAMPEX spacecraft during late 1992 and early 1993. MAST observes a trapped population of heavy ions with ~15 MeV/nuc that includes N, 0, and Ne, but very little C, located in a narrow belt at L=2. The characteristics of this radiation belt are generally consistent with those expected from the mechanism proposed by Blake and Friesen for trapping anomalous cosmic rays in the magnetosphere and with COSMOS observations made during the last solar minimum. We discuss the location, composition, and temporal history of the trapped heavy ions observed with SAMPEX and compare them with properties of anomalous cosmic rays observed in the interplanetary medium. Although trapped He ions are also observed by MAST, it appears likely that they have a different origin.

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