S. M. Korotaev

Interannual changeability in the variations of the vertical component of the electric field in Lake Baikal

The long-term deep-water measurements of the vertical component of the electric field on a surface-lakebed base revealed unexpectedly high interannual changeability in the amplitudes of its variations in periods ranging from a few hours to several months. This changeability almost equally affects the field components caused by the induction in the water flows and, supposedly, by the closing current of the global electric circuit above the rift fault. We present the evidence for the correlation of this effect with the interannual variability in meteorological activity. However, the physical background of this correlation is trivial only for the electric component associated with the induction and still remains unclear for the field component caused by the closing current, which has much higher amplitude.

Long-term observations of the electric field vertical component in Lake Baikal (preliminary results)

A deep-water station is constructed for measuring the vertical component of the electric field on the surface-bottom base. A long-term experiment of measuring the vertical component in Lake Baikal is carried out. The measured signal fully reflects (due to the absence of the telluric component) variations in total flows in the range of periods from a few hours to tens of days. The coefficient of internal turbulent friction is estimated from the divergence between theoretical and experimental periods of the inertial flow. The detection of spectral maximums corresponding to variation periods of the hard component of solar radiation is the most important result of the present study. Possibly, this fact is direct evidence for the global electric circuit closure under suitable regional conditions.

Relationship between variations in the electric field’s vertical component in Lake Baikal and solar activity

Based on the data of deepwater measurements of the electric field’s vertical component in Lake Baikal, the relationship between electric field variations and those in background X-ray solar radiation has been revealed. A high correlation between these variations within periods of more than three months has been discovered.

The effect and precursors of the earthquake of August 28, 2008, in the vertical component of the electric field in Lake Baikal

842 Since 2003, continuous recording of the vertical component of the natural electric field on the bot� tom–surface basis has been performed in Lake Baikal in the basin of the South Baikal deep depression. The instrumental setup is located in the southwestern part of the lake in the region of the Baikal neutrino tele� scope NT�200 (Institute for Nuclear Research, Rus� sian Academy of Sciences). It is a vertical electric antenna grounded in the water with nonpolarizing lead electrodes located at a distance of 1250 m (the depth of the place is 1350 m). The recording of the variations in the field was performed using autono�

Results of vertical electric field monitoring in Lake Baikal

The electric field of the hydrosphere can be used for monitoring various geophysical processes. Practical implementation of such monitoring requires sufficiently reliable measurements of the field and separation of the contributions from different sources. The present work endeavors to successively solve these tasks in the scope of the experiment on monitoring the vertical voltage in Lake Baikal. Similar monitoring has been conducted previously; however, insufficient reliability of the measurements limited the progress in data interpretation. Since then, we have designed a new instrumental complex, capable of highly accurate measurements and controlling the potential noise sources. For the first time, the flow-induced field is compared with the direct flow velocity measurements. The first results show the flow-induced field is predominant at periods of up to ten days. However, this analysis leaves unclear the origin of variations with a period of about 100 days.

Correlation between Long-Term Variations in the Vertical Component of the Electric Field in Baikal and Solar Activity

The vertical component of the electric field along the surface–bottom baseline was measured for several years in the southwestern part of Baikal. The measurements revealed a correlation between long-term variations in the field that were interpreted as variations in the current in the hydrospheric segment of the global electric circuit with intermittent variations in the solar activity. However, the continuous measurement series were no longer than a year, which is shorter than the maximal quasi-period of the alternating variations. The first continuous two-year measurement series was made in 2014–2016. Its analysis shows quite strong variations with quasi-periods of up to 320 days, which correlate with variations in the solar X-ray flux. The effective delay of the correlation is about four days, which is evidence of an indirect effect of solar activity on the vertical current in the hydrosphere by rather slow atmospheric processes.

The results of marine electromagnetic sounding with a high-power remote source in the Kola Bay in the Barents Sea

The first Russian six-component seafloor electromagnetic (EM) receivers were tested in an experiment carried out in Kola Bay in the Barents Sea. The signals transmitted by a remote high-power ELF source at several frequencies in the decahertz range were recorded by six receivers deployed on the seafloor along the profile crossing the Kola Bay. Although not all the stations successfully recorded all the six components due to technical failures, the quality of the data overall is quite suitable for interpretation. The interpretation was carried out by the three-dimensional (3D) modeling of an electromagnetic field with neural network inversion. The a priori geoelectrical model of Kola Bay, which was reconstructed by generalizing the previous geological and geophysical data, including the data of the ground magnetotelluric sounding and magnetovariational profiling, provided the EM fields that are far from those measured in the experiment. However, by a step-by-step modification of the initial model, we achieved quite a satisfactory fit. The resulting model provides the basis for introducing the corrections into the previous notions concerning the regional geological and geophysical structure of the region and particularly the features associated with fault tectonics.

Study of the possibility of the use of the magnetotelluric sounding method in the Arctic ocean with quantitative modeling

The task of the magnetotelluric (MT) sounding of the heterogeneous deep section of the Arctic ocean floor on the idealized model of gorst and graben lying on the typical oceanic, or continental Earth’s, crust is solved with the use of 3D quantitative modeling. In both cases, the sequence is covered by a layer of seawater with a thickness of 4 km. In this work, the difference in the MT sounding with the use of ocean-floor and surface equipment is considered. As a result, the conclusion was made that the floor equipment has a higher resolution than the surface equipment, in spite of the fact that the observations from the ice cover’s surface can be done more easily.

Studies on the effects of the assemblages of the oceanic bottom structures on magneto-variational sounding results

The induction interactions between ensembles of secondary oceanic bottom structures were studied by a 2D conductivity model. It was found that frequent intercalation of such structures lead to significant cumulative effects that had to be taken into account when modeling the structures of the first order. The study was performed for the magnetovariational sounding results obtained in the Arctic Ocean.

Prospects of magnetotelluric sounding in some large structures in the Arctic ocean

In the work, the results of modeling of electric resistivity distribution at the Gakkel and Alpha-Mendeleev underwater ridges are given. Based on the seismostratigraphic models, the apparent resistivity curves at a few points of the profile at the crossing of the ridge were constructed. The advantages and disad-vantages of the MT sounding method are presented. The results obtained can be used for future experiments.