Ground-conductivity determinations at low radio frequencies by an analysis of the sferic signatures of thunderstorms

Abstract

A technique is described for determining the conductivity of the ground at low frequencies with the aid of sferic pulses from thunderstorms. The paper is illustrated with an actual conductivity determination, and the detailed comparison of waveforms predicted theoretically with those observed experimentally indicates that an effective value of conductivity can be measured to a precision of one or two significant figures. The results of the analysis indicate application of both experimental and analytic techniques to other propagation studies, such as the evaluation of the reflection and transmission properties of the lower ionosphere.

Propagation of ground wave electromagnetic signal, with particular reference to a pulse of nuclear origin

“…The theory of propagation of the ground wave of a pulse of low-frequency energy around a finitely conducting spherical earth has been studied in detail by Johler and Walters [ l ] , and Johler and Lilley [2], with particular emphasis on techniques for treating almost any pulse shape. The problem of introducing pulses resulting from ionospheric reflections has been studied by Johler [3], [4].…”

“…The problem of introducing pulses resulting from ionospheric reflections has been studied by Johler [3], [4]. The validity of the theory of the ground wave pulse in particular has been carefully checked experimentally by Johler and Lilley' [2]. Numerous other researches treated theoretically various aspects of the ground wave pulse, such as Wait [SI, [26], Pekeris and Altermann [6], Johler [7], and Van Der Pol [S].…”

“…The pulse is assumed to propagate a distance d to an ob-e2 is the dielectric constant [ t p~1 5 for land or €2-80 for sea water]. The effect of the dielectric constant (displacement currents in the ground) is small a t low frequencies, less than say 300 kc/s, provided the conductivity u is of the order of 5(10-3) mhos per meter or greater, as shown by Johler and Lilley [2]. For purposes of the analysis presented in this paper, a value of €2 = 15 was assumed.…”

“…The expressions ( 6 ) and (8) to be calculated in the foregoing analysis can be summarized in integral form, since the quadrature techniques [2], [3] are applicable to all integrals of this type. Thus, if + ( z ) represents argf(z), and the complex Fourier spectrum of E(t', d2) is…”

“…A few of these papers which have been used extensively for background in this paper are mentioned in the following. Latter and LeLevier [2] have calculated the vertical absorption applicable to the study of riometer measurements due to X-ray, y-ray, and fl-ray radiation of high-altitude nuclear bursts neglecting any ambient ionization. Crain and Booker 131 developed a simple, but general, relation for 2053…”