Whistlers excited by nuclear explosions

The dynamic spectra of whistlers excited by five nuclear explosions are found to be identical to those of natural whistlers observed within a few minutes of shot time. Two shots fired at the Nevada proving ground produce normal two- hop whistlers at Stanford, 600 km to the west. Three shots fired over Johnston Island (about 14 deg N geomagnetic latitude) produce one-hop whistlers, some of which are received at northern hemisphere stations as far away as Stanford, 5100 km to the northeast. No whistlers are observed on Kauai, only 1200 km northeast of Johnston Island. Analysis shows that the magnetospheric paths of natural and explosion-excited whistlers are essentially the same, and that these paths are fixed in the ionosphere and are not necessarily close to the impulse source or the receiver. From analysis of impulse-whistler delays of shot Teak, it is deduced that the one-hop whistler received at Stanford is excited by an impulse that first crosses the equator in the earth-ionosphere wave guide before entering the whistler duct in the southern hemisphere, as suggested in the concept of the hybrid whistler. The high-altitude shot Starfish Prime (July 9, 1962) is detonated at 400-km altitude, but the dispersion of themore » source impulse is similar to that of ordinary lightning impulses. This result is interpreted to mean that the impulse is produced below the ionosphere, thus providing support for the Compton-electron mechanism of impulse generation. The similarity between the natural and shot-excited whistlers leads to the conclusion that shotexcited whistlers cannot be used for the purpose of detecting nuclear explosions. (auth)« less