Low-energy solar protons in the pseudo-trapping region of the magnetosphere

The development of structure in the flux profiles of low-energy (∼2–Mev) solar protons at low altitudes over the polar caps is examined in detail for the event beginning on June 9, 1968. The structure is studied in the frame of reference provided by simultaneous measurements of the trapping boundary for electrons of energy >1.2 Mev and calculations of the boundary of the pseudo-trapping region. The results are interpreted in terms of (1) delayed access of solar protons to the magnetotail, (2) an effect indistinguishable from strong pitch angle scattering near the last closed field lines, owing to breakdown of the adiabatic invariants in the strong curvature of the magnetic field, (3) weak pitch angle scattering on the dayside at low latitudes in the pseudo-trapping region and in the stable-trapping region, and (4) inward diffusion and acceleration in the stable-trapping region.