Inner-zone electrons in 1964 and 1965

Measurements of the fluxes and spectra of energetic (Ee ⪖ 0.8 Mev) electrons were made in 1964 and 1965 with satellites 1964-45A and 1965-78A (OV1-2) in the inner radiation belt. At the time of these measurements the trapped electron flux was still dominated by artificially injected electrons dating from the Starfish test. In December 1964 the peak flux of electrons with Ee ⪞ 4.5 Mev was located at the magnetic equator at L = 1.35; the flux there was 106 cm−2 sec−1. Decay times of electrons (Ee ⪞ 4.5 Mev) at the magnetic equator are 197±22 days at L = 1.25, 442±93 days at L = 1.40, and 373±67 days at L = 1.50. The decay times do not appear to differ significantly for electrons >1.6 Mev. The electron spectrum above 1.6 Mev softens with increasing L for L > 1.5; the spectrum varies only weakly along field lines.