Energetic heavy ions with nuclear charge Z ≧4 in the equatorial radiation belts of the Earth: Magnetic storms

Magnetic storms are known to perturb the earth's radiation belts in profound ways. In this paper we present direct in situ observations of trapped energetic heavy ions with nuclear charge Z ≧4 at energies in the lower MeV range made with Explorer 45 during the period June–December 1972. All measurements were carried out in the vicinity of the geomagnetic equatorial plane (1.0 ≦B/B 0 <1.4), and the data show the varying effects of four major magnetic storm periods. Orders of magnitude increases in the trapped heavy ion population were seen deep within the radiation belts ( L ∼ 2.5–5) following the August 1972 solar flare and magnetic storm events. Fluxes of the Z ≧4 ions were found to decay faster than those of helium ions of comparable energies; typical decay times for Z ≧4 ions are found to be 24–40 days at L ≦4 and shorter at higher L shells. The observations are compared with the expected post‐injection long‐term behavior of atomic oxygen ions deduced from charge exchange, Coulomb collisions, and radial diffusive transport. We report a good agreement between theory and observations.