The Laptev Sea is a unique region, representing a transition zone from the spreading Gakkel Ridge to the rift system, located on the continental margin of Eurasia. In this study, we construct high-resolution distributions of the depths to the top and bottom of the lithospheric magnetic layer (LML) for the Laptev Sea using the centroid method and the EMAG2v3 model of the lithospheric magnetic field. Maximum bottom depths of the LML (45-48 km) are observed under the Siberian Platform, in the north of the Verkhoyansk Range, and under the Lena River delta and Buor-Khaya Bay, while the shallowest bottom depths (<34 km) are attributed to the Eurasia Basin and eastern Laptev Sea. Our results indicate that the coldest lithosphere is attributed to the Siberian Platform. The lithospheric heating is observed under the Eurasia Basin and eastern Laptev Sea; the western part of the shelf, Buor-Khaya Bay, and Lena River delta are characterized by the colder lithosphere. The eastern segment of the Khatanga-Lomonosov Fracture is characterized by a local temperature minimum, evidencing for the spreading axis of the Gakkel Ridge does not continue to the shelf. An area of relatively high temperatures in the east of the shelf passes to the continent through the Yana Bay and covers the Yana-Indigirka lowland. This fact along with the crustal thinning and extension allow us to suggest rifting processes in the considered area.

We consider the thermal state of the lithosphere in the poorly studied region, including the NE flank of the Baikal rift zone and its adjacent areas (110°–122° E, 50°–63° N). For this purpose, spectral analysis of the EMAG2v3 lithospheric geomagnetic field model using the centroid method is performed, average temperature–depth geotherms are calculated from surface heat flow measurements, and the depth to the bottom of the seismogenic layer is estimated from the data on hypocentral depths of regional earthquakes which occurred in 2000–2018. The distribution of the bottom depths of the lithospheric magnetic sources, regarded as the Curie point depths (CPDs) in this study, which are obtained, demonstrates a southward decrease of the CPD values. The shallowest (22.5 km) and deepest (48.5 km) depths are observed in Transbaikalia and at the Siberian Platform, respectively, while the NE flank of the Baikal rift zone is characterized by intermediate CPDs varying from 32 to 44 km. This tendency is clearly seen in the average CPD estimates which are 33, 37, and 40 km in Transbaikalia, Baikal rift, and Siberian Platform, respectively. In Transbaikalia, the average CPDs, estimated from geomagnetic and geothermal data, are close to each other in contrast to the other structures, where the obtained inconsistency could result from a small number and uneven distribution of surface heat flow measurements, their distortion by permafrost and convection, or assumptions about the radiogenic heat production near the surface. The centroid of the magnetic sources is approximately equal or slightly shallower than the seismicity cutoff depth at the NE flank of the Baikal rift. For the major part of the considered territory, the same relation between the CPD and Moho depths is observed, except for two areas at the Siberian Platform and the Vitim volcanic field, where the uppermost mantle is magnetic. Intermediate relative to the Siberian Platform and Transbaikalia, values of the CPD, obtained at the NE flank of the Baikal rift, indicate no significant heating of the lithosphere; they do not agree with a hypothesis of active rifting but provide evidence for its passive character. Article Highlights

The studies of the deep structure and tectonics of the Arctic are important for solving the fundamental problems of modern geodynamics and developing its natural resources. This region is also of interest from the geopolitical point of view, in particular, considering the boundaries of the marginal seas. Our study aims to investigate the lithospheric (anomalous) geomagnetic field in the Norwegian-Greenland region of the Arctic and to correlate the identified anomalies with tectonic structures located in the region under study. The database includes the CHAMP satellite measurements of the modulus of the total geomagnetic field vector (the satellite operated at the altitude of ~280 km). This article describes the satellite data processing method applied to distinguish between the lithospheric part and other components of the geomagnetic field. Map showing the total vector modulus of the lithospheric field has been constructed for the studied area. The article discusses the possible nature of the lithospheric magnetic anomalies and their relation to the processes that occur under the territory of Greenland. According to our interpretation of the maps, the geomagnetic field anomalies are related to the modern large-scale geological and tectonic structures located in the studied area. The obtained results can facilitate further comprehensive geological and geophysical studies and contribute to modeling of the evolution of the lithosphere.

Virtual globes - programs implementing interactive three-dimensional (3D) models of planets - are increasingly used in geosciences. Global morphometric models can be useful for tectonic and planetary studies. We describe the development of the first testing version of the system of virtual morphometric globes for the Earth, Mars, and the Moon. As the initial data, we used three 15'-gridded global digital elevation models (DEMs) extracted from SRTM30_PLUS, the Mars Orbiter Laser Altimeter, and the Lunar Orbiter Laser Altimeter gridded archives. For three planetary bodies, we derived global digital models and maps of several morphometric attributes (i.e., horizontal curvature, vertical curvature, minimal curvature, maximal curvature, and catchment area). To develop the system, we used Blender, the open-source software for 3D modeling and visualization. First, a 3D sphere model was generated. Second, the global morphometric maps as textures were imposed to the sphere surface. Finally, the real-time 3D graphics Blender engine was used to implement globe rotation and zooming. The testing of the developed system demonstrated its good performance. Morphometric globes clearly represent peculiarities of planetary topography, according to the physical and mathematical sense of a particular morphometric variable.

The position of lithospheric magnetic anomalies, de tect d in total magnetic intensity of the magnetic field, has been determine d for Balkan based on the data from the CHAMP satellite and the Global Earth Magnetic A nomaly Grid (EMAG2). The paper describes the technique for the satellite dat a processing and the ways of separation of regional lithospheric magnetic anomal ies from total satellite-measured values of the geomagnetic field. The maps of magnet ic field anomalies for two different altitudes have been constructed for the r egion of Balkan. The possible geologic and physical nature of the magnetic anomal ies and their relationship with deep-seated crustal structures are considered. Prel iminary interpretation of the magnetic field maps shows that the anomalies are co nnected with the present day large geologic and geophysical elements of the base ment. The features of the lithospheric magnetic field, as a parameter reflect ing he present position of tectonic structures and their physical properties, can be us d for their contouring in combination with other geological and geophysical m ethods.

The question about the survival possibility and the life duration of the topside ionosphere equatorial spread F (ESF) plasma bubbles observed in the separate ion component (He+) is investigated. For this aim the main aeronomy processes, in which plasma bubbles and their He+ ions are involved, were under consideration. It was obtained that the main competition takes place between the He+ loss reactions (He+–N2 reaction) and the uplift during linear growth phase (~10min) of the Rayleigh–Taylor (R–T) instability, when the plasma bubbles are forming. It was revealed that the ambipolar diffusion of the He+ ions inside the plasma bubble is the fastest (~1–2min) in the altitude region up to 500km and becomes slower (~1h) above 500km. On the other hand, the plasma bubbles seen in He+ density are pretty stable structures against the cross-field (Bohm) diffusive collapse. It was concluded that the ESF plasma bubbles, reaching the “ceiling” heights, can exist for a night and several morning hours (~10–13h) and that there is a principal opportunity to observe them in the separate ion component (He+).

Magnetic fields and their vertical gradients on a stratospheric balloon on the base of 6 km length are measured. Magnetic anomalies and their gradients are extracted with the use of global magnetic models of the normal field. Magnetic gradients allow to determine places in which there are no significant magnetic anomalies. Ordinates of a profile of the extracted magnetic anomalies in these places are the error of applied global magnetic model of the normal geomagnetic field set at the moment of measurement, and serve as the amendment to magnetic anomalies. It is shown, that only magnetic anomalies at the altitudes numerically equal to thickness of the Earth's crust, are formed of all sources, and its local component is filtered naturally. With the use of the offered technique of extracted of magnetic anomalies it is possible to create strict model of anomaly magnetic field for cosmic circumterrestrial space.

In the last decade, according to the International Geomagnetic Reference Field 2000 (IGRF-2000) and IGRF-2005 models, geomagnetic field weakens with the rate 11-15 nT/year. In this paper we assume that the external source, namely the ionospheric current system controlled by solar activity, contributes to the model. If so, we show - this source provides more than a half to the observed weakening. As the quantitative indicators of solar activity we use the index F10.7, solar wind speed V and the Z-component of interplanetary magnetic field (Bz). Basic data for the model are taken from the CHAMP satellite for May 2001 - December 2005 period. In the analysis, we exclude the trend associated with solar activity from the three main coefficients of the spherical harmonic expansion of the magnetic field and show - the remained weakening is 4-8 nT/year only.

In 2004 European Space Agency approved for full implementation the geomagnetic low-Earth-orbiting (450-550 km of altitude) three-satellite constellation mission Swarm to be launched in 2010. These notes promote the idea to support forthcoming Swarm multisatellite geomagnetic mission with the long duration balloon (LDB) flights aimed to simultaneous measurement of geomagnetic field at stratospheric altitudes (20-30 km).

The description of the stratospheric balloon (aerostat) gradiometer, consisting of three instrumental containers (a mass 20-40 kg of each one) uniformly placed along a vertical 6 kin rope is given. Each instrumental container includes the measurement instrument of geophysical fields, system of data transfer (Globalstar) and GPS-receiver. The parachutes attached to each instrumentation container ensure the safety of an experiment even in the emergency situation case. The system was tested and used as geomagnetic gradiometer for investigation of the anomaly magnetic field and interior structure of the Earth's crust since 1988.

The stratospheric balloon magnetic gradiometer system is developed and maintained at IZMIRAN already about 20 years. This system consists of three instrumental containers uniformly placed along a vertical 6 km line. System allows measuring parameters of the geomagnetic field along the whole flight trajectory. The GPS-receivers, located in each instrumental container, fix the flight coordinates. The developed launching technology, deployment in flight, assembly, data, transfer and processing, landing the containers with the equipment can be used for other similar problems of monitoring and sounding an environment. Useful flight weights of each instrumental container may be reaching 50 kg.