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2022 | Buch

Problems of Geocosmos–2020

Proceedings of the XIII International Conference and School

herausgegeben von: Dr. Andrei Kosterov, Dr. Nikita Bobrov, Dr. Evgeniy Gordeev, Dr. Evgeniy Kulakov, Dr. Evgeniya Lyskova, Dr. Irina Mironova

Verlag: Springer International Publishing

Buchreihe : Springer Proceedings in Earth and Environmental Sciences


Über dieses Buch

This book addresses the problems of Geocosmos and provides a snapshot of the current research in a broad area of Earth Sciences carried out in Russia and elsewhere.

The themes covered include solar physics, physics of magnetosphere, ionosphere and atmosphere, solar-terrestrial coupling links, seismology, geoelectricity, paleomagnetism and rock magnetism, as well as cross-disciplinary studies.

The proceedings are carefully edited, providing a panoramic outlook of a broad area of Earth Sciences. The readership includes colleague researchers, students and early career scientists. The proceedings will help the readers to look at their research fields from various points of view.

Problems of Geocosmos conferences are held by Earth Physics Department, St. Petersburg University bi-annually since 1994. It is the largest forum of this kind in Russia/former Soviet Union attracting up to 200 researchers in Earth and magnetospheric physics.



Exploration and Environmental Geophysics

Segmentation of the Earth’s Crust of the Tien Shan by Geophysical Data

The paper presents the results of a comprehensive analysis of geological studies with data on the deep structure obtained by various geophysical methods for the Tien Shan territory. The areas of junction of different tectonic segments are characterized by anomalies of increased electrical conductivity, are clearly manifested in the magnetic and gravity fields and correspond to the zones of deep faults. Studying of these objects having high permeability and providing heat and mass flow as well as transport of fluids, is the main object of this work. In order to identify the boundaries of the largest tectonic fragments of the Tien Shan the geoelectric and velocity sections along the profiles intersecting the main tectonic elements of the Tien Shan were analyzed. Comparison of velocity anomalies in seismotomographic sections and objects of abnormally low electrical resistivity in geoelectric sections of the Earth’s crust indicates the existence of zones of increased fracturing or plasticity in the indicated intervals of the Earth’s crust, as well as the coincidence of waveguides and zones of increased conductivity. The distribution of seismic events clearly shows the zones of the Northern, Middle and Southern Tien Shan and the segmentation of the Western and Central Tien Shan.

E. A. Bataleva, V. E. Matiukov
Experiment FENICS-2019: Exploration of Electrical Conductivity of the Eastern Fennoscandinavian Shield with Grounded Sections of Power Transmission Lines (In Memory of Abdulkhay Azimovich Zhamaletdinov)

The deep electromagnetic (EM) sounding of the lithosphere carried out in the frame of the FENICS-2019 experiment from 12 to 21 September 2019 in terms of experimental layout was a frequency domain sounding with the source of two grounded industrial power lines operating in the frequency range of 192.2–0.382 Hz. The measurements were mostly carried out by the research team from Geological Institute of the KSC RAS (GI KSC) within 841 km from the source. The additional measurements by stations of the Polar Geophysical Institute, Luleå University, Nizhny Novgorod Radiophysical Research Institute (NIRFI) and the Institute of Geosphere Dynamics of the Russian Academy of Sciences (IDG RAS) were carried out at distances of up to 1470 km. The results obtained in GI KSC RAS were processed and consolidated into a database of apparent resistivity and impedance phase curves, calculated for the absolute values of the total electric and magnetic fields. The principal novelty of the FENICS-2019 experiment, distinguishing it from the AMT-MT sounding, was the quantitative account for static shift at each point. The method of correction for static shift is based on measurements of the apparent resistivity from the total horizontal magnetic field of the controlled source. Magnetometer sensors are not galvanically coupled to the Earth and therefore not affected by static shift. The method for assessing the static shift was applied within the far zone; it accounts for the influence of the ionosphere and displacement currents. Geoelectric sections were constructed for four observation profiles. This work was carried out in the frame of the state assignment of the Ministry of Education and Science of the Russian Federation for GI KSC RAS (topic No. 0226-2019-0052, FMEZ-2022-0025) and supported by the Russian Foundation for Basic Research (grant No 18-05-00528).

A. N. Shevtsov, A. A. Skorokhodov, A. E. Hannibal, T. G. Korotkova, V. V. Kolobov, M. B. Barannik, V. V. Ivonin
Specifics of the Earth’s Crust Structure in the Potential Gas Hydrate Accumulation Zones of the Arctic Basin

Due to the favorable thermobaric conditions of gas hydration in the Arctic Basin, mathematical modeling gives a positive forecast for potential zones of methane hydrate accumulation, assuming a very extensive distribution of hydrocarbons. The gas hydrate zones in the Arctic Basin are very extensive and represent a huge resource of hydrocarbons. Layers of hydrates serve as an impervious cover for oil deposits. They create conditions for the formation of near-surface oil and gas accumulation in the form of solid gas hydrates. The unstable state of gas hydrates can cause explosive destruction of these arrays with the sudden release of methane. The fluid systems of the Earth’s crust of the main types of the Arctic cryolithozone, the western and eastern oceanic sectors of the Arctic Basin and coastal-shelf cryolithozones are studied on the basis of density and magnetic sections. Thermofluid channels and lenses of fluid layers in the form of zones of reduced density and magnetization are traced on deep sections. Analysis of the lithosphere density sections of confirmed and potential zones of gas hydrate accumulation revealed deep-focus fluid lens systems at depths of 40–50 and 70–90 km. The areas of fluid flow exits along fault zones from fluid-saturated layers to areas with favorable conditions for the accumulation of gas hydrates are outlined on the basis of a complex interpretation of geophysical data. In the presence of a seismic event, vertical thermofluid channels can activate gas fluid flows. Thermofluidic flows can act as a trigger for explosive destruction of hydrates, creating extra risks for navigation and infrastructure of the Northern Sea Route.

A. A. Petrova, O. V. Latysheva, A. I. Petrova
Deep Factors of Ice Destruction of the Arctic Ocean

The analysis of satellite observations of annual and seasonal changes in the thickness of perennial Arctic ice in the period from 2007 to 2020 showed that the vertical fluid channels of deep-lying fault zones play an important role in the process of transformation and degradation of the ice cover. They contribute to the local destruction of ice with the formation of melt ponds, affect the variability of the thickness of perennial ice and the formation of the edge of ice of different ages. The results of the complex interpretation of magnetic anomalies, gravity anomalies, and seismic and seismological data allowed us to improve the model of the deep structure of the main tectonic structures of the Arctic Ocean. The directed influence of thermal flows of deep fault zones on the localization of ice cover destruction in the zones of fluid-carrying channels exits to the ocean bottom surface in the water area of the Northern Sea Route is revealed.

A. A. Petrova, O. V. Latysheva, A. I. Petrova
Verification of the Arctic Magnetic Field Component Model Based on Observations on the CHAMP and Swarm Satellites

The article presents the results of comparing anomalies of the Arctic’s magnetic field in near-earth space with empirical data measured by the CHAMP and Swarm spacecraft at altitudes of 400 and 450 km. Magnetic anomalies were calculated using a three-dimensional component model of the Earth’s magnetic field of the SPbF IZMIRAN. To identify the features of the deep structure of the lithosphere of Arctic’s magnetoactive zones observed in near-Earth space, sections were constructed based on the surface values of magnetic anomalies. The paper studies the density properties of the magnetic zones of the lithosphere, determines the location, magnetization, thickness and density characteristics of the layers of the lithosphere that create magnetoactive zones in outer space. Density sections are constructed based on gravity anomalies, taking into account seismological data. The study of the information content of magnetic anomalies in near-Earth space in the altitude range from 300 to 600 km is of great scientific and practical importance for solving geological and geophysical problems and questions of spacecraft navigation.

A. A. Petrova, O. V. Latysheva, A. I. Petrova
Interpretation of Component Geomagnetic Field Measurements Carried Out on Board a Ferromagnetic Vessel from the Round-the-World Expedition of the R/V “Admiral Vladimirsky” in 2019–2020

During the anniversary round-the-world expedition of the R/V “Admiral Vladimirsky”, the magnetic field components were measured using two 3-component magnetometers with torsion and magnetoresistive sensors developed at SPbF IZMIRAN. In total, about 60,000 linear kilometers were covered with the measurements. Testing of the obtained results was carried out by comparison with the data obtained on the non-magnetic schooner “Zarya” in the Gulf of Finland and the Bay of Biscay. For the first time, the hodograph method was used to determine the horizontal H component. In particular, this method was used to estimate the position of the South Magnetic Pole. The obtained results showed that despite the complexity of magnetic measurements on a ferromagnetic vessel, such a survey is promising, but further development of the data processing method is required.

S. A. Ivanov, S. A. Merkuryev, I. M. Demina, V. A. Soldatov, D. B. Zaitsev
Integration of Geophysical Methods for Solving Inverse Problems of Exploration Geophysics Using Artificial Neural Networks

The inverse problem (IP) of exploration geophysics consists in reconstructing the spatial distributionf of the properties of the medium in the Earth’s interior from measurements on its surface. This IP is a non-linear ill-posed ill-conditioned problem with high dimensionality both by input and by output. One of the approaches free of many shortcomings inherent for traditional methods of IP solving, is the use of artificial neural networks (NN). In this study, it has been suggested to use an integration of geophysical methods to improve the quality of the solution obtained by NN. The considered model combines three geophysical methods: gravimetry, magnetometry, and magnetotellurics. The problem considered is that of determining the structural boundaries separating the geological layers with constant values of the parameters: density in gravimetry, magnetization in magnetometry, electrical resistivity in magnetotellurics. In this study, a four-layer 2D model was considered. It is demonstrated that integration of geophysical methods provides significantly better results that use of each of the methods separately. It is also shown that in some cases it is also possible to improve the quality of the IP solution using multitask learning—simultaneous determination of the positions of two or all three layer boundaries.

Igor Isaev, Ivan Obornev, Eugeny Obornev, Eugeny Rodionov, Mikhail Shimelevich, Sergey Dolenko
A Versatile Software for Statistical Data Analysis and Spatial Correlation

Development of new tools for interpreting of and maximizing the amount of information extracted from georeferenced experimental and observational data remains an important task of computational geoscience. One of powerful tools for data analysis is the examination of correlation dependence between different, sometimes seemingly unrelated parameters. However, the correlation analysis of geospatial data can often be hampered by inadequate sampling or lack of coincidence between coordinates in the compared datasets. The number and capabilities of affordable software that can be used for these purposes are limited. Here we present a versatile software package for correlation analysis of spatial geo-referenced data with an additional set of tools. The software is implemented as a web service and contains a toolset for performing a geographic coordinate conversion, data interpolation, mapping, spatial correlation, data visualization and other auxiliary functions for spatial data analysis. The performance of the software is checked and confirmed on the real data. We call this service “UNCORR”—the UNiversal CORRelation tool.

Dmitry Krivopaltsev, Leonid Surovitskii, Mikhail Lukin

Paleo-, Earth-, Rock-, Environmental Magnetism, and Geophysical Fluid Dynamics

Magnetostratigraphic Constraints on the Position of the Tremadocian–Floian Boundary at the Key Section of the Moyero River Valley (Siberian Platform)

The magnetostratigraphic study of the geomagnetic reversal frequency just before the Ordovician Moyero superchron can be very useful for testing various geodynamic conceptions and different geodynamo models describing the geomagnetic field evolution. In terms of completeness of the geological record, the Ordovician carbonate-terrigenous key section of the Moyero River valley, located in the northern part of the Siberian Platform, is considered to be one of the best Ordovician sections of Northern Eurasia and seems to be very promising to carry out such a study. However, the Tremadocian part of the section, which could record the pre-superchron reversal history, until now remained poorly studied and exact positions of its boundaries with underlying Upper Cambrian and overlying Arenigian (Floian) strata are still not well determined. In this study we present magnetostratigraphic data, which taken together with obtained biostratigraphic data, allow constraining the position of the Tremadocian–Arenigian (Floian) boundary within the key Moyero River section.

Vladimir Pavlov, Andrei Dronov, Alexander Larionov, Tatiana Tolmacheva
Upper Cretaceous Paleomagnetism and Magnetostratigraphy of the Pur-Taz Interfluve (Northern West Siberia)

Upper Cretaceous magnetostratigraphy of northern West Siberia has been reconstructed using new paleomagnetic data from five wells in the Kharampur oil-gas-condensate field (1049, 109N, 106P-Yu, 105N, and 2073N). The scientific motivation of this investigation was to construct a composite Upper Cretaceous magnetostratigraphic section of the north of Western Siberia based on integrated paleomagnetic and biostratigraphic data, which represent a part of the Upper Cretaceous magnetic polarity scale of all Western Siberia. The study area is located within the Middle Pur trench in the Pur-Taz interfluve. Natural remanent magnetization in the samples of the Pokur, Dorozhkovo, Okhteurievka, Kuznetsovo, Lower Berezovo, and Upper Berezovo Formations was analyzed by stepwise alternated field (AF) and thermal demagnetization and used to compile the magnetostratigraphic sections of the five wells. Correlations among the well sections form a basis for a composite magnetostratigraphic record of Upper Cretaceous (Cenomanian through Campanian) strata in the area. The composite section comprises two normal polarity zones NK2(sn-st) and NK2cp and correlates with the regional Upper Cretaceous magnetostratigraphic section of southern West Siberia, as well as with the global polarity time scale.

Z. N. Gnibidenko, A. V. Levicheva, L. G. Smolyaninova, V. A. Marinov, N. N. Semakov
The First Paleomagnetic Data on the Ust-Obor Section (Western Transbaikalia, Buryatia)

We present detailed rock magnetic and paleomagnetic data of the key Ust-Obor section in Transbaikalia (Buryatia, Russia). The section consists of two parts—the lower loamy sediment unit of Eopleistocene age and the upper sandy sediment unit of Neopleistocene age. The lower unit contains a stratotype fauna complex of Late Eopleistocene age. The paleomagnetic study presented herein reveals only normal polarities of natural remanent magnetization throughout the section. Paleomagnetic results appear at odds with paleontological data, which constrain the lower unit to Eopleistocene age and consequently to the reversed-polarity Matuyama chron. Rock magnetic and paleomagnetic data do not support a remagnetization hypothesis to explain this apparent contradiction. Conversely, the statistically similar rock magnetic and paleomagnetic data of the upper (Neopleistocene) and lower (Eopleistocene) units suggest a common depositional environment and thus a similar geological age. The preferred hypothesis explaining the observations calls for a re-deposition of the Late Eopleistocene Ust-Oborian fauna within younger Neopleistocene sediment.

A. Yu. Kazansky, G. G. Matasova, A. A. Shchetnikov, I. A. Filinov
Preliminary Rock Magnetic and Paleomagnetic Data from a 14.5 m Core of Lake Kotokel Sediments (Baikal Region)

Lake Kotokel is a medium-size freshwater lake located close to the eastern coast of the Lake Baikal. Kotokel lake lacustrine sediments preserve a unique archive of vegetation and climate history for at least the last 46 kyr. Here we present the first preliminary rock magnetic and paleomagnetic data for Lake Kotokel. A 14.5 m long sediment core was retrieved from a water depth of 3.6 m in the southern part of the lake. Magnetic susceptibility (MS) and its anisotropy were measured from 385 oriented samples. The characteristic component of the natural remanent magnetization (ChRM) was obtained using stepwise alternating field (AF) demagnetization. Results of our rock magnetic analyses were interpreted in conjunction with available paleoclimatic and paleobotanical data. The response of magnetic properties to climatic changes is illustrated by the correlation of MS values with vegetation change in the region as indicated by spore-pollen and diatom data. The ancient geomagnetic field is poorly recorded in the studied sediments. Paleomagnetic directions in the upper part of the core are randomly distributed due both to very weak remanence as well as to mechanical perturbation of sediments, most likely caused by degassing processes in soft gyttja. Unstable and scattered ChRM directions result from secondary mineralogical modifications, such as dissolution of primary magnetic grains and growth of secondary magnetic minerals, caused, in turn, by environmental changes in the study area.

A. A. Shchetnikov, A. Yu. Kazansky, I. A. Filinov, G. G. Matasova
Determination of the Position of the South Magnetic Pole Based on Experimental Data Obtained During Russian Round-the-World Expeditions: 1820 (F. Bellingshausen) and 2020 (R/V “Admiral Vladimirsky”)

During the round-the-world expedition of the R/V “Admiral Vladimirsky” (2019–2020), following closely the route of the voyage of Bellingshausen and Lazarev in 1819–1821, a large amount of magnetic data was obtained, including in the Antarctic region. One of the goals of this research has been to determine the position of the South Magnetic Pole (SMP) from experimental data. This was the reason to return to the declination data obtained during the Bellingshausen expedition and to determine the position of the SMP from these data. Several methods have been devised for this purpose. To determine the current position of the SMP, a small polygon survey in the area of its assumed position has been made. The polygon location was chosen based on the forecast of the IGRF-12 model. The three-component measurements on board the R/V “Admiral Vladimirsky” and scalar outboard measurements have been performed and estimates of the current position of the SMP obtained.

I. M. Demina, V. G. Boyarskikh, S. A. Merkuryev, S. A. Ivanov, V. A. Soldatov
Evolution and Statistics of the Geomagnetic Energy and Its Characteristic Timescales Since 1840

The evolution of total (integrated from the core-mantle boundary to infinity) geomagnetic energy based on the COV-OBS.x1 geomagnetic field model is approximated by exponential functions with an error less than 3% in four time intervals between 1840 and 2020. Characteristic timescale is determined as a ratio of the energy to its time derivative (T = E/P, where P = dE/dt has a meaning of power). Timescale values are statistically explored with annual resolution. Most of the timescales (87%) are negative, indicating decrease of energy with characteristic times of the order of thousand years. The remaining 13% indicate the energy increase with the minor timescales of about a few thousand years. The median timescale is − 1176 years, the arithmetic mean is + 1889 years and the most probable or mode Mo = − 483 years. The large standard deviation and RMS (44,571 and 44,400 years) indicate heavy tails which are clearly seen in the bimodal probability density distribution. We define a special geometric mean timescale (− 174 years) which is consistent with the known convective velocities ~ 0.3 mm/s and the observable magnetic heterogeneities drifts. The prevalent timescales are from ~ 500 years to a few thousand years. Corresponding characteristic velocities or the mean field alpha effects ensure a subcritical geodynamo regime. The results are also consistent with periodical and spectral estimates from geodynamo simulations and geomagnetic field models for both the modern era and the ancient geomagnetic field. We estimate roughly that a comparable timescale for magnetic field is about a factor of two longer than T, while the magnetic field periodicity may be several times longer.

S. V. Starchenko, S. V. Yakovleva
Heat Transfer Analysis of Tangentially Rotating Fluid Flow Past a Semi-infinite Vertical Cylinder Kept in Uniform Horizontal Magnetic Field Using Non-linear Regression and Back-Propagation Neural Network

Understanding of the fluid flow over a vertical cylinder is important in many geophysical and technical applications. This paper addresses the numerical simulation of transient natural convective flow passing a uniformly heated semi-infinite vertical cylinder. The fluid is assumed to be viscous, incompressible and tangentially rotating. The cylinder is assumed to be kept in a uniform horizontal magnetic field, which is applied normal to the vertical axis of the cylinder. The closed-form solutions of governing non-dimensional transient coupled non-linear boundary layer equations are obtained numerically using the Crank-Nicolson implicit finite difference method. The momentum and heat transfer coefficients are expressed as average skin friction $$\overline{\tau }$$ τ ¯ and heat transfer rate $$\overline{Nu}$$ Nu ¯ , respectively, for distinct Ekman number (Ek) and magnetic parameter (M) values. The results obtained show that the flow and heat transfer characteristics are significantly influenced by these parameters. Based on the response surface methodology (RSM), the nonlinear regression equation of fitted line response data for $$\overline{Nu}$$ Nu ¯ is obtained for different values of control parameters, such as Ek, M, Prandtl number (Pr) and Grashof number (Gr). The regression coefficients are considered until third order for achieving a more accurate solution and their significance is analyzed using variance (ANOVA) method. The maximum value of $$\overline{Nu}$$ Nu ¯ is obtained by using the optimization technique. Artificial neural network (ANN) model is used to predict $$\overline{Nu}$$ Nu ¯ value for a specified control parameters input. The multi-layer feed-forward network was trained by an algorithm of Back-propagation. It has been observed that the ANN model shows reasonably good agreement with numerical outcomes, so it is regarded as a trusted modeling method. The Kappa coefficient, a quantitative measure of reliability for two raters that are rating the same thing, was calculated from the data obtained using the Crank-Nicolson method, non-linear regression equation and ANN model. The Kappa values obtained by all three methods are perfectly consistent.

Hari Ponnamma Rani, Koragoni Naresh, Yadagiri Rameshwar, Sergey V. Starchenko
Numerical Flow Analysis in Shaped Enclosure: Energy Streamlines and Field Synergy

Understanding heat transfer becomes more important as the severity of climate, either hot or cold, increases. Managing heat flows is critical to occupant’s thermal comfort, durability, energy efficiency, and, increasingly, thermal resilience during periods of extended power outages. In the present study, the convective air flow in the differentially heated gamma ( $${\Gamma }$$ Γ ) shaped enclosure is simulated numerically. Isothermal temperature conditions are assumed at the vertical walls of the enclosure in which the temperature of the step wall is higher than that of other vertical walls. Top and bottom walls of the enclosure are considered to be adiabatic. The governing equations of the problem are discretized using the finite volume approach. To accelerate these simulations, the message passing interface (MPI) protocols are employed using the OpenMPI standard library. High-resolution simulation results are presented. We compare our results with those obtained by state-of-the-art methods to validate the performance of employed numerical methods. The flow behavior is elucidated with the aid of streamlines, isotherms, energy streamlines and synergy between the velocity and temperature gradient vectors by varying the control parameter, Rayleigh number, in the laminar regime.

Hari Ponnamma Rani, Vekamulla Narayana, Yadagiri Rameshwar, Sergey V. Starchenko


The Lake Baikal Unified Scaling Law for Earthquake Regional Coefficients

Seismic hazard assessment requires an adequate understanding the earthquake distribution in magnitude, space, and time ranges. Lacking data for a period of several thousand years makes probabilistic approach to estimating the recurrence time of earthquakes unreliable. Nevertheless, the probabilistic seismic hazard assessment (PSHA) maps keep actively refined both at global and national scales. At the same time alternative models and methods are being developed to improve the accuracy and reliability of reproducible seismic hazard maps that pass intensive testing of historical evidence and simulated scenario earthquakes. One of those, the neo-deterministic seismic hazard assessment (NDSHA) provides reliable and effective tools for understanding and mitigating object-oriented earthquake risks. Consider the unified scaling law for earthquakes (USLE) as a part of NDSHA. USLE is generalizing the Gutenberg-Richter relationship (GRL) as log10N(M, L) = A + B(6 − M) + Clog10 L, M− ≤ M ≤ M−, where N(M, L) is the number of magnitude M earthquakes in an area of linear size L, A characterizes the average level of seismic activity in terms of the annual rate of earthquakes of magnitude M = 6, B is the ratio N(M)/N(M − 1), C estimates fractal dimension of the set of epicenters, and [M−, M−] is the range where the relationship holds. Naturally, C complements to A and B (analogous to a and b of GRL) showing how the number of earthquakes changes with an area linear size. Recent studies have shown that using the USLE provides adequate estimation of seismic hazard at national or even regional scale when the existing earthquake data are a few decades long and rich enough in magnitude determinations.

Anastasiya Nekrasova, Vladimir Kossobokov
Clustering as One of Scenario of Development of Instability: An Earthquake Case

The scenarios of development of bifurcations in different natural systems are believed to be similar. One of the examples of the development of bifurcation is the case of earthquakes, perhaps the mostly studied due to its practical importance and the amount of available data. However, even in this case the scenario of development of instability remains to be unclear. The method of examination of generalized vicinity of large earthquake is applied to reveal the typical scenario of development of seismic instability. Besides of the fore- and aftershock cascades two other types of precursor behavior were found. The time clustering of the main events and a moderate increase in background seismicity since several years before the large earthquake occurrence were found. Taking into account the uniformity of scenarios for the development of instability in systems of different nature, similar modes of instability development probably can origin also in other systems.

M. V. Rodkin, M. Yu. Andreeva, E. V. Liperovskaya
Possible Relationship of Some Weak Earthquakes in Turkey with Industrial Explosions

Possible industrial explosion effects on weak earthquake seismicity in Turkey are considered. The spatial and temporal relationships between the studied events within short periods of time and over short distances, as well as their probable long-term effects, are investigated. Potential correlation between normalized distributions of daily and weekly earthquake and explosion numbers is estimated. Possible changes in the fractal dimension of the spatial seismicity distribution in connection with industrial explosions are studied. To search for spatially compact regions of explosions and local earthquake groups, the method of identifying clusters was applied. Clusters of explosions and earthquakes that are closely spaced have been found. In these clusters, the indicated time series behavior was compared. The significance of the observed temporal and spatial changes is assessed by the method of creating artificial catalogs, as well as by constructing inverse statistics of the earthquake-explosion.

V. I. Zhuravlev, A. Ya. Sidorin, A. A. Lukk
Horizontal Velocity Inhomogeneities of the Mantle Under Central Asia from Rayleigh Wave Phase Velocities

Deep velocity structure of the upper mantle of the continent of Asia was investigated on the basis of a representative dataset of phase velocity dispersion curves of Rayleigh waves. A method of surface-wave tomography developed for a spherical surface was applied to obtain phase velocity distributions in the period range 10–200 s. Average dispersion curves were calculated for various tectonic regions and then inverted to vertical S-wave velocity sections up to the depth of about 600 km. The obtained results allow us to explore main features of the deep velocity structure of the upper mantle under the considered region.

Oxana A. Solovey
Various Scale PS ECWM-CDP Seismic Prospecting for Crustal Structure Studies

We construct depth sections of deep crust in the range from 0.8 to 1.2 km (low velocity zone) to 40–60 km (the upper mantle) by jointly using the active seismic data and the results of the PS converted wave method (PS ECWM). Crustal blocks and the boundary zones of different areas including the Onega-Ladoga Block, South Karelia were identified and delineated. Their geomorphological and geodynamic characteristics were described. Comparison of the deep sections of various mineralogenic provinces shows that in spite of the minor differences in evolution and the modern geodynamic settings, they have a lot in common, particularly: (1) All sections reveal tectonic (mantle) zones that extend through the crust and control the velocity contrast at the Moho discontinuity. These zones were commonly rejuvenated during various activation epochs. (2) Presence of strong waves converted at the velocity contact of the Moho boundary (disintegration and elevated geodynamic tension zones). (3) There is a wedge-like zone in the upper part of the earth crust, where no converted waves occur («silence zones»). (4) This domain always adjoins the tectonic (mantle) zone in the middle crust at 10–20 km depth. Similarities of the ore zones makes possible using of analogy in the prognostic studies for various mineralogenic provinces. Additionally, the RWM-CDP sections from the Salmi and Svir-Oyat prospects were constructed for depth varying from 1–2 to 300 m. Seismic microzoning (SMZ) was carried out as a part of the integrated areal seismic and seismological studies. It led to the assessment of the current state of the grounds and to delineation of areas of unconsolidated ground together with the geodynamically weakened (consequently, less stable) zones of possible residual deformation. Thus, the SMZ maps show seismic hazard differentiation for this area.

E. V. Isanina, N. V. Sharov, S. I. Yuzhaninova
Evaluation of Hypocenters Distribution Based on the Geoelectric Models in the Tien Shan Earthquake-Prone Areas

This work is aimed to develop a new approach to study the relationships between the spatial distribution of the electrical conductivity and earthquake hypocenters in seismically active regions such as the Tien Shan. The basis of a complex deep complex model (up to 30 km depth) of the Tien Shan lithosphere is a fault-block model. The joint analysis of the geoelectric model and seismicity provides important information for understanding the distribution of deep electrical conductivity, which is an indicator of active geodynamic processes and provides indirect estimates of the stress-strain state of the geological media. The purpose of our investigation is to extend the study of the relationship between hypocenter depth distribution and geoelectric boundaries on a 2D cross-sections in the Central Tien Shan. This paper shows complex models, built for several meridional magnetotelluric soundings (MTS) profiles located (74.3° E and 75.2° E). We use seismic bulletins for 5 years (2015–2019) and select earthquakes nearest to the MTS profile lines. Based on our previous studies, we are interested in the behavior of seismicity with energy classes K < 8 and K > 8 separately. We calculate relative coordinates (latitudes) to the kilometers from the starting point of the profile. As a result, the graphs present colored 2D cross-section with profile distance (R) and earthquake hypocenters into the depth marked by dots. The analysis of this study indicates the presence of a certain relationship: the earthquakes hypocenters clustering attach to the boundaries of objects and outline geological bodies, or are located inside certain zones.

Kseniia Nepeina, Elena Bataleva
Application of Adaptive Filtering Techniques for Filtering Induced Seismic Noise

The complexity and versatility of modern research requires the development and improvement of methods and tools for the operational processing of seismic data. Often, the main task in seismic data processing is to efficiently and reliably extract useful components from the recorded signal for their further use. Obviously, in this case, seismologists need to use the entire arsenal of methods and algorithms for reducing in modern information-measuring systems induced noise caused by various kinds of dynamic processes. An adaptive filter can be proposed as one of the options for solving such problems of filtering a seismic signal in the presence of interference caused by various kinds of dynamic processes. This article is devoted to the problems of using adaptive filters to separate seismic signals with simultaneous digital recording of a seismic signal and atmospheric pressure. The article shows that using adaptive filtering, it is possible to significantly improve the signal-to-noise ratio and successfully to separate seismic signals masked by induced interference. Thus, using the adaptive filtering method, it is possible to solve the problem of improving the data quality of seismic instruments by removing unwanted induced noise from them.

V. V. Gravirov, K. V. Kislov
On the Question of the Rotational Seismometry Metrology

Rotational seismology is a relatively new area of science, which was formed in the past 20 years. During this time, new instruments were created; interesting data was obtained and verified; and main directions for further development of rotational seismology were identified. Now a much greater number of observations are required for further development of rotational seismology. We need to create networks for recording of rotational movements, which should be taken parallel to the traditional seismometrical measurements. This requires development of appropriate metrological standards. It is necessary in order for the seismological data to be useful. More detailed views on this issue are presented in this work.

V. V. Gravirov, K. V. Kislov
Variations of Ambient Temperature and Following Them Instrumental Noise of Seismic Instruments

Seismological study requires data of sufficient quality. To this end, it is necessary to understand how to deal with noise caused by non-seismic sources. It is essential to eliminate or reduce the noise occurring in the seismic devices when external temperatures oscillate. At present, high-performance computers allow solving almost any specific problem numerically, and theoretical search for analytical solutions seems unproductive. However, a lack of theoretical knowledge can lead to the emergence of research using vast resources ineffectively. For appropriate evaluation of the cause of noise, it is necessary to understand how external temperature variations penetrate to each element of the device, what the attenuation and phase shift. Theoretical studies are undoubtedly useful in investigating the applicability of sensors, in the development of new sensors, in the development of methods for their installation. Analytic approach in the most general form can be applied to any type of seismic equipment.

V. V. Gravirov, K. V. Kislov

Solar-Terrestrial Physics

Dose Rate Bursts Onboard the ISS and the “Lomonosov” Satellite in the Earth’s Outer Radiation Belt

The EXPOSE-R2 experiment was carried out by the European Space Agency on board “Zvezda” module of the ISS. The R3DR2 device was one among the EXPOSE-R2 instruments. The semiconductor detectors were sensitive elements of the R3DR2 device that permit to measure radiation doses behind thin shielding. The results of this experiment are freely available now. We used them to analyse variations in the radiation environment at ISS altitude in the Earth’s outer radiation belt. SINP MSU carried out a similar experiment on board The “Lomonosov” satellite. One of its devices DEPRON instrument includes semiconductor detectors. The detectors were similar in design to those in the R3DR2 instrument. The analysis showed the presence of significant enhancements in dose rate. The dose rate of such enhancements reached the level of 28.8 mGy/h according to R3DR2 data and 106.5 mGy/h according to DEPRON data. However, the total dose rate of single enhancements did not exceed 0.8 mGy according to R3DR2 data and 1.6 mGy according to DEPRON data. Comparison with geomagnetic conditions showed that such enhancements are observed mainly during periods of geomagnetic disturbances. The obtained information may be used to estimate the level of radiation impact in the region of the Earth’s outer radiation belt.

G. I. Antonyuk, V. V. Benghin, T. P. Dachev, O. Yu. Nechaev, I. A. Zolotarev, V. L. Petrov
Kamchatka Meteoroid Effects in the Lithosphere–Atmosphere–Ionosphere–Magnetosphere System

A few physics and mathematics models of the processes in all geospheres that were caused by the fall of the meteoroid has been performed. Mechanical, optical, gas-dynamic, thermodynamic, magnetic, electrical, electromagnetic, ionospheric, seismic, plasma, plume, turbulence, acoustic-gravity wave effects that accompanied the fall of the Kamchatka meteoroid have been estimated. The energy release (about 5 × 1014 J) has been shown to take place mainly at altitudes of 26–30 km, where the rate of mass loss reached about 1 kt/s, and deceleration about 6 km/s2. Near the terminal height, the speed of the meteoroid decreased by about 10%, and its mass by 20%. The main parameters of the shock wave have been considered; the energy and power of the shock wave were estimated to be about 580 TJ and 58 TW; near the epicenter of the meteoroid detonation, the pressure at the shock front was ~1 kPa; the perturbations in atmospheric pressure at ionospheric heights above the epicenter of the detonation attained tens and even hundreds of percent. The energy and power of the fireball light were about 130 TJ and 1 PW respectively. The size of the heated region and its temperature (about 4600 K) have been estimated, and the four stages of its cooling have been considered. The main parameters of the debris trail (dust and plasma densities, as well as electric and magnetic field strengths) and the parameters of electromagnetic and Alfvén pulses have been estimated. The mechanisms for the generation of acoustic, atmospheric gravity, ion-acoustic, and magnetosonic waves, as well as instabilities, have been considered. The parameters of the emerging cloud of dust, as well as the duration and rate of its settling, have been estimated.

L. F. Chernogor
Features of Ionospheric and Magnetic Effects of August 5–6, 2019 Noticeable Geospace Storm Over China and Ukraine

An increase in the main parameters of the solar wind on August 5, 2019 led to a geospace storm, which was observed mainly on August 5 and 6, 2019. The main phase of the magnetic storm took place on August 5, 2019 from 06:00 UT to 08:30 UT. The recovery phase lasted at least 4 days. The magnetic storm manifested itself in significant variations in all components of the geomagnetic field, an increase by an order of magnitude in the level of oscillations of the geomagnetic field in the range of 400–950 s. During the ionospheric storm, the ionospheric F-region was significantly disturbed. The ionospheric E-region remained weakly perturbed. The ionospheric storm significantly affected the Doppler spectra of radio waves in the 5–10 MHz frequency range. The Doppler spectra exhibited significant broadening, and variations in the Doppler shift of frequency and its quasi-periodic changes occurred with a period of 20–40 min and duration of 120–240 min.

Leonid F. Chernogor, Yu. Zheng, Q. Guo, Y. Luo, K. P. Garmash, V. T. Rozumenko
About Petschek-Type Reconnection Driven by Inhomogeneous Plasma Resistivity

Applying a two-dimensional, compressible Hall magnetohydrodynamic (MHD) model, we study reconnection of magnetic fields in various cases: symmetric and non-symmetric antiparallel magnetic fields, and also skewed magnetic fields. The magnetic reconnection process is initiated by switching on a localized resistivity assumed to be a Gaussian function of spatial coordinates. As initial condition we set a one-dimensional steady-state current sheet. The obtained numerical solution indicates that reconnection process evolves asymptotically to the stationary Petschek-type regime in the case of inhomogeneous resistivity. The internal reconnection rate is found to be proportional to square root of the inverse local magnetic Reynolds number. The external reconnection rate is found by matching the external Petschek solution and the internal diffusion region solution for various cases of steady-state two-dimensional reconnection in a compressible plasma. The obtained general formula for the reconnection rate yield those of Sweet–Parker or Petschek in particular cases of pure homogeneous or strongly localized resistivity. In case of skewed reconnecting magnetic field, the reconnection rate is proportional to the sine of angle between magnetic field and reconnection line. The Hall parameter is found to be responsible for generation of the so called Alfvén wings structure. These wings are related to the Hall MHD Alfvén waves propagating faster than the usual Alfvén waves in the ideal MHD model. The obtained Alfvén wings are characterized by intensive field-aligned currents and large variations of the out-of-plane magnetic field and velocity components.

N. V. Erkaev, V. S. Semenov
Sensitivity of Surface Meteorology to Changes in Cloud Microphysics Associated with IMF B

In recent decades, the response of surface meteorology to the variation of the B $$_{y}$$ y component of the interplanetary magnetic field (IMF) at high latitudes, known as the Mansurov effect, has been extensively studied. However, the role of the global electric circuit (GEC) in these processes is still unclear. Recent studies suggested that the response of cloud microphysics to IMF B $$_{y}$$ y -induced changes in cross-polar cap potential and fair weather downward current density J $$_{z}$$ z may be one of the possible ways for solar wind-surface meteorology coupling. Such a mechanism requires confirmation, but numerical studies that would show the Mansurov effect discovered in observations have not been carried out earlier. In this work, we evaluated a sensitivity of surface meteorological parameters to a certain change in the stratiform-cloud autoconversion rate imposed by the IMF B $$_{y}$$ y -related changes in the J $$_{z}$$ z using the chemistry-climate model SOCOLv3. It should be noted that in this first study, we use the non-realistic approach where the IMF B $$_{y}$$ y -induced anomalies staying constant for the whole period of simulation. Nevertheless, we found that even small changes of $$\pm 12$$ ± 12 % in the J $$_{z}$$ z and corresponding changes in the autoconversion rate in regions where IMF B $$_{y}$$ y -induced anomalies in the cross-polar cap potential occur, can lead to large-scale anomalies in surface pressure (up to 2 hPa) and air temperature (up to $$1.5\,^{\circ }$$ 1.5 ∘ K) at high and middle latitudes that are in good agreement in magnitude with those detected in observations. This study shows the importance of further investigating solar-terrestrial coupling through the GEC using global climate models.

Arseniy Karagodin, Irina Mironova, Eugene Rozanov
UV Pulsations in the Auroral Region According to Measurements on the Lomonosov Satellite

The Lomonosov satellite was launched into a 97.3° polar sun-synchronous orbit on April 26, 2016, and operated in orbit until December 2017. The TUS detector is a highly sensitive telescope, designed for both detection of ultra-high-energy cosmic rays and the Earth’s atmosphere UV-radiation in the 240–400 nm range. To measure variety of atmospheric phenomena the telescope has four modes of operation with different temporal resolutions (from 0.8 µs to 6.6 ms). Among the events recorded above 50° N in the mode with a temporal resolution of 6.6 ms, 66 were identified with an unusual spatiotemporal structure, representing local pulsations of glow in the field of view of the instrument. Geographical distribution was analyzed and it was shown that events are mainly located in the area of equatorial boundary of auroral oval (more than half of events were registered on L-shells 4–6). Characteristic frequencies of pulsations of glow intensity are of the order of 1–10 Hz, and areas of pulsating glow are localized in the space with characteristic horizontal size of 10–15 km. A comparison with the THEMIS ground-based all-sky cameras was made. 11 joint observations were found and the presence of aurora lights at the time of TUS events registration was shown by ground-based cameras, although no obvious coincidences of pulsations were found.

P. A. Klimov, K. F. Sigaeva
Polar Cap ULF Pulsations: Coordinated Radar-Magnetometer Observations

This study uses multi-instrument geomagnetic and ionospheric observations in Antarctica to examine the causative mechanisms of the ultra-low-frequency (ULF) variations of the electrodynamics of the polar cap—the least explored part of the coupled solar wind-magnetosphere-ionosphere system. The ionospheric oscillations corresponding to Pc5–6 pulsation band (quasi-periods about 3–15 min) were detected by SuperDARN Mac-Murdo radar. The ground geomagnetic response B was examined using magnetometers at polar latitudes in Antarctica. We have selected events with quasi-periodic variations of the ionospheric Doppler velocity V and simultaneously observed by ground magnetometers. Supposedly, this class of events is produced by magnetospheric MHD waves. We have determined the effective wave impedance, that is V/B ratio, which enabled us to identify the physical nature of specific polar cap pulsations. This type of polar Pc5–6 pulsations has been associated with Alfven mode, though the occurrence of periodic disturbances in the region with open or strongly extended field lines seems puzzling.

O. V. Kozyreva, V. A. Pilipenko, X. Shi, E. C. Bland, L. Baddeley
The Asymmetry of Magnetospheric Configuration and Substorms Occurrence Rate Within a Solar Activity Cycle

The aim of this work is to test the hypothesis by Kivelson and Hughes (Kivelson and Hughes in Planet. Space Sci. 38:211–220, 1990), according to which, for asymmetric configurations with a curved current sheet and large curvature of magnetic field lines in the tail of the magnetosphere, the substorm breakdown threshold decreases. The work used two databases on the substorms onset: (1) (Frey et al. in J. Geophys. Res. 109:A10304, 2004)—4700 events for 2000–2005, and (2) SUPERMAG—18,800 events for 2000–2010 (Gjerloev in J. Geophys. Res. 117:A09213, 2012). OMNI data was used for the solar wind parameters. We try to answer the question what solar wind parameters are responsible for the bending of the current sheet in the tail of the magnetosphere, how these parameters affect the number of emerging substorms, and what structures of the solar wind are capable of carrying them. Among these possible factors of symmetry break, we explore the alfvénic-type excitations, the dipole tilt, and the direction of solar wind flow, which were traced within the solar activity cycle. As a result, we found a notable correlation (R = 0.65) of yearly substorm occurrence rate and the yearly amount of earthward propagating alfvénic disturbances, while no correlation (R = 0.01) was observed for substorms and sunward propagating alfvénic fluctuations. We also found that the yearly averaged absolute value of dipole tilt at a substorm explosion is always larger (by 0.5°–2.0°) than the mean value of absolute dipole tilt and the difference is larger during the solar cycle maximum when substorm occurrence rate also maximizes. The above difference becomes about 0.5° larger if we take into account the effective tilt angle and consider the input of solar wind flow direction to the actual dipole tilt. We also show that the averaged AL-index for a portion of substorms, which occurred under the dipole tilt less than 8° was −244 nT, and the AL-index for substorms with larger tilt (20°–30°) was −192 nT, which gives more than 20% difference.

Marina Kubyshkina, Vladimir Semenov, Nikolai Erkaev, Evgeniy Gordeev, Igor Kubyshkin
Lightning Activity of Eruptive Clouds from Shiveluch Volcano (Kamchatka, Russia)

One of the local features of the Kamchatka Peninsula is volcanic lightning and aeroelectric formations resulting from volcanic eruptions. When an eruptive cloud (EC) arises and is formed, it becomes electrified, which leads to the occurrence of numerous lightning strikes. This indicates a significant role of electrostatics in the formation of EC even for weak eruptions and demonstrates the informative value of volcanic lightning for estimating the EC size. The article presents cases of recording of thunderstorm activity using a VLF direction finder (30 Hz–40 kHz) located 390 km from Shiveluch volcano. Based on its data, electromagnetic pulses (EMP) from volcanic lightning for 14 explosions were recorded for the period 2017–2019. The number of pulses per minute, EMP counting rate (v), was taken as the parameter characterizing the process intensity. Two phases are distinguished in v dynamics depending on eruption character and intensity. Phase I characterizes the eruption beginning character. A peak-like phase I, lasting up to 5 min, is observed for the eruptions, which begin with magma fragmentation according to an explosion scenario. For the eruptions, which begin according to a «smooth» scenario, only phase II can be observed. It characterizes lightning activity of a developed eruptive cloud.

Evgeniy Malkin, Pavel Firstov, Nina Cherneva, Gennadiy Druzhin
Dynamic Characteristics of Field-Aligned Ionospheric Irregularities Under the Conditions of Ionosphere Modification

Telecommunication systems of decameter range are applied to transfer information for long distances. However, electromagnetic radiation suffers significant attenuation determined by re-reflection from the ground surface. These losses can be considerably decreased if the propagation would take place in an interlayer ionospheric waveguide. The idea to apply the interlayer ionospheric waveguide for data transfer was formulated quite a long time ago but its practical implementation is hampered by the problem of effective excitation of the interlayer ionospheric waveguide and radiation coupling. One of the possible ways to solve this problem is the application of scattering on magnetically oriented irregularities of the ionosphere. It is known that scattering on irregularities is accompanied by fading. In the works, carried out in this area of investigation by the specialists of Kharkov Institute of Radio Astronomy, scintillation index was used to estimate fading. The index allows one to calculate the fading level quantitatively. In addition, it is considered that the best approximation of signal intensity distribution is Nakagami distribution. Taking into account irregularity motions, intensity distributions, which are significantly different from those used for the scintillation index calculation, are possible. Thus, it is topical to investigate intensity distributions, for example, from the power of impact on the ionosphere. The attempt to carry out such a study is made in this paper.

Vladimir Sivokon’, Nina Cherneva
Estimation of the Parameters of Field-Aligned Ionospheric Irregularities in the Area of Active Impact

Ionospheric irregularities significantly affect radio-technical and telecommunication systems. The degree of this influence depends on the electromagnetic radiation range of these systems and irregularity properties. In recent times the possibilities of generation of artificial ionospheric irregularities by heating facilities are under intensive investigation. The facilities include a powerful decameter-range transmitter and a directed antenna. In the result of such impact on the ionosphere, electron concentration irregularities, including magnetically oriented ones, are formed. The irregularities are the structures aligned along the Earth’s magnetic field lines. Their longitudinal dimension is many times as large as their lateral dimension. A heating wave is intensively scattered on such irregularities. It is known as a self-scattering effect (Galushko et al. in Radiofizika i radioastronomiya—Radiophys. Radioastron. 17(2):112–124, 2012 (in Russ.) [1]). In this case, the scattering character is determined by irregularity parameters and topology (Sivokon’ et al. in Elektromagnitnye volny i elektronnye sistemy—Electromag. Waves Electron. Syst. 24(8):23–28, 2019 (in Russ.) [2]). On the basis of these features of magnetically oriented irregularities and applying the network of SDR receivers, located within the line-of-sight of the impact area, we investigate the dependence of irregularity motion velocity variations and direction on the intensity of impact on the ionosphere.

Vladimir Sivokon’, Nina Cherneva
Uncertainty of Sunspot Parameters Reconstructed from Early Telescopic Sunspot Observations

We present the results of the reconstruction of the parameters of solar activity from astronomical observations in the seventeenth century. Drawings of the solar disk made by various observers differ in the observing methodology and accuracy. The distribution of the sunspot group areas from historical archives was compared with that of the modern epoch. A lack of small groups of sunspots was found in early observations. This, in turn, leads to an uncertainty in the number of sunspot groups in tens of percent. Additional uncertainty of group numbers is introduced by sorting the sunspots into groups. The latitude-time distribution of sunspots is also discussed.

Nadezhda Zolotova, Mikhail Vokhmyanin
Problems of Geocosmos–2020
herausgegeben von
Dr. Andrei Kosterov
Dr. Nikita Bobrov
Dr. Evgeniy Gordeev
Dr. Evgeniy Kulakov
Dr. Evgeniya Lyskova
Dr. Irina Mironova
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