HF radio measurements of high-altitude acoustic waves from a ground-level explosion

Abstract

Linear acoustic theory predicts that a large ground-level explosion--several hundred tons of TNT should produce a pressure wave amounting to several per cent of ambient in the atmosphere 200 km above the explosion. Analysis of the interaction of such a pressure disturbance with the ionosphere implies that the passage of the wave should be readily measurable by means of vertical-incidence radio phase-path soundings. Radio measurements made at the time of a 500-ton explosion have confirmed the hypothesis. The shape of the observed phase disturbance agrees well with that predicted, and the observed onset times check to within 10 seconds with acoustic ground-to-ionosphere travel times. The amplitude and duration of the disturbances were approximately 100 radians and 2 minutes, respectively. The amplitude is slightly smaller than predicted; however, the observed duration is approximately twice that calculated. Refining and fitting the model to obtain better agreement--especially in disturbance onset time, shape, and duration--may represent a technique for improving present estimates of the upper-atmosphere density molecular weight and temperature.

Recent Advances and Difficulties of Infrasonic Wave Investigation in the Ionosphere

“…When a high-frequency radio wave is reflected from the ionosphere, a movement of the reflection point will produce a change in signal phase path and hence a Doppler shift, proportional to the time rate of change of the phase path. The first measurement of high-altitude acoustic waves from a ground-level chemical explosion was carried out using this method (Barry et al, 1966). They measured phase differences (u) between the oscillations of the received signal and the oscillations of a reference frequency generator (first method).…”

“…Kazakhstan scientists made the first measurement of ionospheric effects due to an underground nuclear explosion at the Semipalatinsk Test Site in 1978 . Barry et al (1966) were the first to describe ionospheric disturbances induced by a large surface chemical explosion. To test the potential of the ionospheric method, the first special chemical explosion (Mill Race, USA) was carried out on 16 September 1981 (Warshaw and Dubois, 1981).…”

A model for conjugate coupling from ionospheric dynamos in the acoustic frequency range

“…Our essential requirements on the wave, namely that its frequency be near the micropulsation frequency, and that its propagation be normal to B [Jacobson and Bernhardt, 1985-1, appear to be met by at least portions of either disturbance. Barry et al [1966] first reported HF observations of acoustic waves at ionospheric heights arising from a ground-level explosion. Later, Jones and Spracklen [1974] described HF Doppler perturbations following the accidental Flixborough explosion.…”

Electrostatic effects in the coupling of upper atmospheric waves to ionospheric plasma

“…Our treatment is confined to oscillations of sufficiently high frequency that both plasma diffusion and chemical processes have a negligible effect on the plasma response to the neutral motion. In practice, our treatment will be relevant for acoustic waves of both artificial origin [Barry et al, 1966;Rickel and Simons, 1982;Blanc, 1984] and seismic origin [Davies and Baker, 1965;Wolcott et al, 1984] as well as for short-period acoustic gravity waves (for a review, see Yeh and Liu [1974, and references therein]). The electrostatic solution will be shown to predict certain novel effects in the electron density perturbation, which may be observable by radio frequency propagation diagnostics.…”