Thermal Near Field and the Possibilities of Its Use for In-Depth Temperature Diagnostics of Media

Abstract

We discover experimentally the effect of an electromagnetic thermal near field of a lossy medium. The effective depth deff of the layer in which the received signal is formed is found to be less than the skin-layer depth dsk and is a function of the size D of the receiving antenna and its height h above the medium surface. The dependence deff(D,h) is obtained from measurements of the emission from a temperature-stratified water medium at a wavelength of 31 cm using a specially developed, electrically small antenna. The results of experimental studies of radiophysical parameters of the antenna are presented. We propose to use measurements of the dependence of the received emission on D and h as a new source of information on the in-depth temperature distribution. Methods for solving the corresponding inverse problems are developed, and the first results of retrieval of the subsurface temperature profile of a water medium are obtained.