Very low frequency phase perturbations and the soviet high-altitude nuclear bursts of October 22 and 28, 1962: 1. Observations and inferred radiation belts

Abstract

On October 22 and 28, 1962, nuclear explosions over central Asia produced ionospheric D-layer perturbations as monitored on various VLF paths in the northern hemisphere. Delayed VLF effects due to trapped particles averaged 53% of the normal diurnal change for the burst of October 22, and 29% for the burst of October 28. The types of particles and their energies were the same for both detonations, but differences existed in the spatial extent of the radiation belts producing the VLF phase perturbations. The trapped particles were electrons with E ≲ 4 Mev and protons in the range 2.3 to 4.6 Mev. The electron spectrum is composed of fission and neutron-decay β particles, the latter predominating for E < 0.78 Mev. Protons <2.3 Mev may have also been present, but those with E < 1 Mev cannot penetrate into the D region and are of no direct VLF interest. With the dipole field approximation, for the detonation of October 22, fission and neutron-decay β particles were trapped in a region bounded by field lines intersecting the earth's surface in a range extending at least from 36.5° to 56° geomagnetic (for the real field the shells are 1.75 ≤ L ≤ 3.76). For October 28, fission β particles were confined to areas <49°N (L < 2.32) and probably to field lines around that passing through the burst point (at 36.5°N and L = 1.75); this type of confinement also existed for 2.3- to 4.6-Mev protons after both nuclear bursts. For October 28, effects due to neutron-decay β particles were found at 49°–51°N (2.32 ≤ L ≤ 2.79), a region which formed the outer boundary for these trapped particles. For the burst of October 22, a prompt effect was observed on the GBR to APL transmission.