Solar activity and whistler dispersion

Abstract

Since early 1956, the very-low-frequency phenomena known as whistlers have been observed regularly and simultaneously at several locations in North America and in New Zealand. Various whistler characteristics are tabulated and exchanged within the above network. One of the characteristics reported is the time-delay between the occurrence of the atmospheric “bonk” (Morgan and Dinger, 1956) from a nearby lightning flash and the arrival of the associated whistler which has made the double-transit journey through the outer ionosphere, being guided by the earth's magnetic field to the opposite hemisphere, and back again (Storey, 1953; Morgan and Allcock, 1956). Since a whistler consists of a falling tone, lasting for perhaps a second, the time-delays are measured from the bonk to the appearance of the highest audible component of the whistler, normally in the vicinity of 5 kc/sec.