Anomalous Cosmic Rays: The Principal Source of High Energy Heavy Ions in the Radiation Belts

Abstract

Recent observations from SAMPEX have shown that "anomalous cosmic rays" are the principal source of high energy(> lOMeV /nuc) heavy ions trapped in the radiation belts. This component of interplanetary particles is known to originate from interstellar atoms that has been accelerated to high energies in the outer heliosphere. The mechanism by which anomalous cosmic rays with ,...., 1 to ,...., 50 Me V / nuc are trapped in a radiation belt at L ~ 2 has now been verified. We discuss models for accelerating and trapping anomalous cosmic rays and review observations of their composition, energy spectra, pitch angle distribution, and time variations. Extrapolation of the fluxes observed at ,...., 600 km to higher altitude and other time periods is also discussed.