Energetic magnetospheric ions at the dayside magnetopause - Leakage or merging?

The leakage model for the escape of energetic magnetospheric particles into the magnetosheath is described, making comparisons with the merging model where possible. Reported observations of energetic particles at the dayside magnetopause are reexamined, and it is concluded that they do not conclusively support the merging model, either on a case-by-case basis or statistically. New observations made by the Charge Composition Explorer satellite during the Active Magnetospheric Particle Tracer Explorers program are presented. They indicate that magnetospheric ions of all species steadily escape into the magnetosheath and stream away from the magnetopause, regardless of the magnetosheath magnetic field orientation. It is concluded that the leakage model explains both the new and old observations at least as well as, or better than, the merging model.