Geomagnetically trapped alpha particles: 2. The inner zone

Abstract

The inner zone population of trapped α particles in the energy range 2.14–9.0 Mev was measured during 1969. The measurements show that inner zone α particles are strongly peaked in pitch angle and that the intensity decreases rapidly with decreasing L value. The α particle spectra are flat and closely resemble inner zone proton spectra at comparable energies. The α/p ratio is roughly independent of L (1.6 ≲ L ≲ 2.0) and energy (0.293–1.14 Mev/nucleon) and is ∼1–4 × 10−3. The computed α particle distribution function strongly suggests that the inner zone is populated by α particles that diffuse inward, conserving M and J. A value of the diffusion coefficient is derived, DLL = 1.2 × 10−8 L10 day−1, that is in good agreement with earlier proton studies.