Geomagnetic Origin for Transient Particle Events from Nuclear Reactor--Powered Satellites

Transient events observed since 1980 by the Gamma-Ray Spectrometer experiment on the Solar Maximum Mission satellite (SMM) have been identified with radiation emitted from 18 different Soviet nuclear reactor--powered satellites. Most of these satellites are similar to Cosmos 954 and 1402 which reentered the atmosphere. Gamma radiation from these satellites was detected when they passed within about 400 to 500 kilometers of SMM. Positron annihilation line radiation (511 kiloelectron volts) and charged-particle events were detected when SMM encountered clouds of positrons and electrons emitted by these satellites and stored up to tens of minutes in the geomagnetic field. The rate of these events varied from about 1 in 5 days to over 30 per day and was strongly dependent on the operating altitudes of the Cosmos satellites and density of the upper atmosphere.