Project Jason measurement of trapped electrons from a nuclear device by sounding rockets

Solid-propellant rockets were sent to altitudes of 800 km from three stations in the eastern United States to observe electrons injected into the geomagnetic field from a small high-altitude nuclear detonation. The electron flux was measured by an assembly of Geiger counters. Shortly after a nuclear detonation above the south Atlantic, a narrow region of high counting rate was observed. The geometry of the observations is related to the geomagnetic field. The region consisted of an intense band about 20 km wide (half-width at half maximum counting rate) and less intense wings extending at least 700 km north and perhaps 700 km south of the band. Neither position nor width of the band changed during the observations, which consisted of periodic soundings until 100 hr after the nuclear detonation. The intensity of both the wings and the band decayed during the measurements as 1/t, which is consistent with the hypothesis that small-angle scattering is the dominant loss mechanism. The angular distribution of the radiation was measured, and the electron flux was observed to be confined very nearly to a plane perpendicular to the field lines. Spectral measurements show far fewer electrons above 4 Mev than were expected from the fission beta spectrum. Betas trapped from the decay of neutrons emitted from large-yield high-altitude weapon tests in the Pacific were also noted.