Application of Waves with Circular Polarization in Magnetotelluric Sounding

Abstract

Abstract —We consider the possibility of using circular polarizations, which make the field vector in a wave rotate clockwise or counterclockwise, as independent polarizations of the primary wave during magnetotelluric sounding (MTS). This approach has been proposed for the first time to search for possible manifestations of the Hall effect under natural conditions during MTS; in this case, if the effect is small, waves with circular polarization become normal modes in a horizontally layered medium located in the constant magnetic field of the Earth. Standard impedance relations are replaced by the corresponding apparent resistance impedances and curves for waves with circular polarization (mode). In the search for manifestations of the Hall effect during MTS, it becomes necessary to determine differences in the mode apparent resistivity curves due to the presence of lateral inhomogeneities of the medium. This study deals with the specific features of MTS in the case of representing the primary source field by circular polarization waves. Results of the theoretical analysis of mode impedances are demonstrated. Numerical simulation is used to investigate the differences in the mode impedances and curves depending on the nature of the distribution of lateral inhomogeneities in the medium. Mode apparent resistivity curves obtained by processing the experimental data of the MTS in Gorny Altai are presented. It is shown that, in comparison with standard curves, mode curves are subject to less distortion by lateral inhomogeneities of the medium owing to the specific features of distributions of the charges and currents excited by circular polarization waves in them.