Initial observations of geomagnetically trapped protons and alpha particles with OGO 4

Two totally depleted solid-state detectors with thicknesses of 34 and 7.2 microns designed to measure protons and alpha particles, respectively, were launched into a near-polar orbit on the OGO 4 spacecraft. Both detectors have four electronically determined energy channels. Initial results, based on data obtained on August 8 and 27, 1967, show the following: (1) the ja/jp ratio is ∼7 × 10−4 and 2 × 10−4 for particles of E ≳ 0.35 and 0.46 Mev/nucleon, respectively; (2) the observed ratio ranges from 2 × 10−4 for E ≳ 0.46 Mev/ nucleon, to 2.4 × 10−3 for E ≥ 0.68 Mev/charge, to 1.9 × 10−2 for Etotal ≥ 1.06 Mev when the proton and alpha particle intensities are compared on the basis of equal energy/nucleon, equal energy/charge, and equal total energy, respectively; (3) there are indications that the ratio ja/jp decreases as the energy/nucleon increases. Comparison of the data with various predictions of models that consider the solar wind as source of trapped particles show serious discrepancies between theory and observations.