V.V. Plotkin

Nonlocal electromagnetic response: Implications in the regional sounding

Due regard was given to the nonlocal electromagnetic responses in the processing of the data of the International Baltic Electromagnetic Array Research (BEAR) 1998 Project. Maps of lateral distributions of the apparent electrical resistivity for different time periods were compiled. In these maps, the main tectonic boundaries between the Lapland-Kola, Karelian, and Svecofennian tectonic provinces within the Baltic Shield appear as zones with reduced apparent electrical resistivity. There is supposedly some correlation between the positions of the maxima in electrical resistivity and the maximum Moho depths. In the same way, the data from the network of geomagnetic observatories in the European region (the INTERMAGNET Project) were processed for 2004–2005, and maps of the laterally inhomogeneous distribution of the apparent resistivity in Europe have been compiled for different time periods. The correlation is observed between the positions of the minima in the electrical resistivity and the minima in the thickness of the lithosphere.

Approaches to the estimation of lateral heterogeneity of the upper mantle by electromagnetic methods

The paper addresses the construction of maps showing lateral distributions of the apparent electrical conductivity in various time periods from data of the worldwide network of observatories. The lateral distribution of the apparent conductivity of the Earth is determined by a self-consistent estimation of variations in three components of the geomagnetic field recorded at all stations. The results of processing of data on daily geomagnetic variations observed at the worldwide network in 1964–1968 are presented.

Spin crossover and Mott—Hubbard transition under high pressure and high temperature in the low mantle of the Earth

Effect of high pressure induced spin crossover on the magnetic, electronic and structural properties of the minerals forming the Earths low mantle is discussed. The low temperature P, T phase diagram of ferropericlase has the quantum phase transition point Pc = 56 GPa at T = 0 confirmed recently by the synchrotron Mossbauer spectroscopy. The LDA+GTB calculated phase diagram describes the experimental data. Its extension to the high temperature resulted earlier in prediction of the metallic properties of the Earths mantle at the depth 1400 km < h < 1800 km. Estimation of the electrical conductivity based on the percolation theory is given. We discuss also the thermodynamic properties and structural anomalies resulting from the spin crossover and metal-insulator transition and compare them with the experimental seismic and geomagnetic field data.