JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 68, FEB. 1, 1963, P. 685-699. 23 REFS.
Numerical integration of a Fokker-Planck equation including atmospheric scattering and energy loss has been used to predict the time decay of electrons injected into the geomagnetic field by the July 9, 1962, nuclear explosion over Johnson Island. Calculations were performed for L = 1.18, 1.25, and 1.30 using an atmospheric characteristic of sunspot minimum and averaged over longitude, keeping L and B fixed. Deviations of the calculated and observed spatial distribution at one week after the injection are attributed to the overly simplified initial conditions. The early decay follows closely the form T/(t + T) and is followed by an exponential decay at later times. For L = 1.25, T varies from 104 sec at B = 0.21 to 107 sec at B = 0.16 (the equator). The exponential decay for L = 1.25 has a mean life of 1.3 x 108 seconds. Decay is accompanied by spectral hardening. After any substantial decay the spectrum is peaked at about 1.5 Mev.