The phenomenology of the mass motion of a high altitude nuclear explosion

The persistence of the free expansion of the detonation products of a high altitude detonation is determined by the sum of the stresses of the environment. Below 200 km the classical dynamic friction with the air couples the detonation products to a very much larger mass of air. Above this altitude more uncertain plasma phenomena of magnetic and electrostatic shocks must be considered to determine this coupling. If a cubic scale height of air is raised to a temperature such that its sound speed is greater than escape velocity, it jets upward, and the ionized fraction is stopped and mixed unstably with the earth's magnetic field. The subsequent expansion along the field lines deposits the major fraction of the debris at the opposite conjugate point. The β ‐particle decay in transit on the various L surfaces reached by unstable mixing determines the high energy electron injection into trapped orbits. For the Starfish event (1.4 megatons at 400 km), theory predicts that the detonation products and a cubic scale height of air expand upward until stopped by the earth's field at 1000 km. In addition, we expect the deposition of the debris in the atmosphere at the southern conjugate point at 250‐km altitude to be dispersed over 300 km owing to magnetic field mixing. Approximately 5% β injection into trapped orbits of L >1.3 is expected.