Geophysical Journal | 2001 volume 23 1

Transient electromagnetic processes in an expanded time interval: physico-mathematical models and features

© Shuman V.N.

The problem of founding a physico-mathematical model of the method of field formation with recording an electromagnetic echo in an expanded time range is considered. The attention is concentrated on two key problems: elements of the marhematical apparatus and peculiarities of matrial characteristics of real media; physical treatment of the electromagnetic echo structure (Wave solutions of different types).
Certainly, it is the modes and the rays which are two central senses of the electromagnetic wave propagation theory. It is shown that the phenomenological theory of the field formation with recording early and superearly stages can be effectively formed only within the scope of the electrodynamics of material media with considering both the frequency and the spatial dispersion. In this aspect, no of presently used equations provides a complete description of the process of the electromagnetic disturbations propagation in a real multiphase heterogeneous medium. Theresore, the numerical calculations and the ray approximations in estimating and interpreting an electromagnetic echo are not alternative and even not competitive. A specific question of the analogies between the seismic method and the sounding by field formation in a superearly time range is considered in detail. A generalization of the usual conception of grouped velocity of propagation in a weakly absorbing medium clearly unambiguos only for wave packets is given for the case of an arbitrary wave form.

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