Propagation of Pulses Over an Irregular and/or Inhomogeneous Earth, Comparison of the Theory and the Experiment

Beyond and direct line-of-sight ground wave propagation measurements were made over two different propagation paths 49 km and 55-4 km in length. Data were collected during the St-Privat d ’Allier experimen­ tal compaign in 1983 in France. Results presented here include a comparison between measured and predicted pulses. The predictions are based on the paper AMRI et al (l). Measured pulses demonstrated the usefulness of the method developped in;this late paper in providing amplitude and wave-form predictions. INTRODUCTION The propagation of electromagnetic pulses over an irregular and/or inhomogeneous earth by ground wave is of considerable interest. The introduction of sensitive solid state devices into the industrial plants makes these devices more susceptible to the electroma­ gnetic pulses and, there fore may require additional protection. In this context, it has become evident thg£ more knowledge regarding the propagation of the elec­ tromagnetic pulses is required. Such knowledge can be acquired theoretically by the method developped by the authors in the preceding publication (l). Here, we will compare some of our experimental results obtained in 1983 at the lightning triggering station at St-Privat d'Allier (France) with that obtained theoretically. THEORY OF PULSE PROPAGATION We know that the transient field E(t,r0) at a time t and a distance r0 on the surface of the earth is related to the continuo us time-harmonic solution E(jti), ro), assuming a linear amplitude response of the medium of propagation, by the Fourier transform-integral theorem (6) (2j : E(t,r ) = J e3Mt E(jio, ro) M(ju)do) (1) where M(jto) is the Laplace transform of the moment m(t) of the source +°° M(j