Satellite observations and numerical simulation results for the comprehensive analysis of ash cloud transport during the explosive eruptions of Kamchatka volcanoes

Ash clouds resulting from explosive volcanic eruptions pose a real threat to human life (for aircraft flights, airport operations, etc.); therefore, the detection, monitoring, and forecast of their movement is an urgent and important issue. The features and examples of application of the new tool developed on the basis of "Monitoring of Active Volcanoes of Kamchatka and the Kurile Islands" information system (VolSatView) are described. It allows the integrated monitoring and forecasting of ash cloud transport using the data of remote sensing and mathematical modeling as well as the assessment of the parameters of explosive events.     

Launching of conical winds and axial jets from the disc–magnetosphere boundary: axisymmetric and 3D simulations

We investigate the launching of outflows from the disc–magnetosphere boundary of slowly and rapidly rotating magnetized stars using axisymmetric and exploratory 3D magnetohydrodynamic simulations. We find long-lasting outflows in the following cases. (1) In the case of slowly rotating stars , a new type of outflow, a conical wind , is found and studied in simulations. The conical winds appear in cases where the magnetic flux of the star is bunched up by the disc into an X-type configuration. The winds have the shape of a thin conical shell with a half-opening angle  θ∼ 30°–40°  . About 10–30 per cent of the disc matter flows from the inner disc into the conical winds. The conical winds may be responsible for episodic as well as long-lasting outflows in different types of stars. There is also a low-density, higher velocity component (a jet) in the region inside the conical wind. (2) In the case of rapidly rotating stars (the 'propeller regime'), a two-component outflow is observed. One component is similar to the conical winds. A significant fraction of the disc matter may be ejected into the winds. The second component is a high-velocity, low-density magnetically dominated axial jet where matter flows along the opened polar field lines of the star. The jet has a mass flux of about 10 per cent of that of the conical wind, but its energy flux (dominantly magnetic) can be larger than the energy flux of the conical wind. The jet's angular momentum flux (also dominantly magnetic) causes the star to spin down rapidly. Propeller-driven outflows may be responsible for the jets in protostars and for their rapid spin-down. The jet is collimated by the magnetic force while the conical winds are only weakly collimated in the simulation region. Exploratory 3D simulations show that conical winds are axisymmetric about the rotational axis (of the star and the disc), even when the dipole field of the star is significantly misaligned.     

Lyman-alpha observations of venera-9 and 10 I. The non-thermal hydrogen population in the exosphere of venus

The dayside hydrogen exosphere was observed in October–November 1975 with a Lymanalpha photometer carried on board Venera-9 and 10. In addition to intensity measurements, the use of a hydrogen cell allowed for the first time linewidth measurements. Both intensity and linewidth measurements below 1500 km of altitude are well fitted by a single exospheric component (T_c = 500 ± 100 K, n_c = 1.5 × 10⁴ atom cm^?3at 250 km). Above 3000 km, the measured linewidth increased sharply, to decrease again above 4500 km. This feature is interpreted as the signature of an additional population of “hot” atoms circulating on satellite orbits, created just behind the bow-shock by charge-exchange collisions (with an efficiency of 4%) between the neutral atoms and the solar wind protons, which became turbulent after bow-shock crossing. The density ratio of “hot” to standard population is of the order of 10% around 3500 km of altitude.     

Geomagnetic and Ionospheric Responses to the Interplanetary Shock Wave of March 17, 2015

The propagation of perturbation caused by the interplanetary shock wave of March 17, 2015 from the solar wind through the magnetosheath, magnetosphere, and ionosphere down to the Earth’s surface is analyzed. The onboard satellite measurements, global magnetometer network data, and records by the receivers of the global positioning system (GPS) providing the information about the total electron content (TEC) of the ionosphere are used for the analysis. By the example of this event, various aspects of the influence of the interplanetary shock wave on the near-Earth environment and ground-based engineering systems are considered. It is shown which effects of this influence are well described by the existing theoretical models and which ones need additional research. The formation of the fine structure of the magnetic impulse of the storm sudden commencement (SC)—the preliminary impulse (PI) and main impulse (MI)—is considered. The MI and compression of the magnetospheric magnetic field is observed by the GOES and RBSP satellites and on the geomagnetically conjugate stations; however, the PI was only noted on the Earth. The PI was detected in the afternoon sector practically simultaneously (within 1 min) with the shock wave impact on the magnetopause. The wave’s response to the SC includes the strongly decaying resonant oscillations of the magnetic shells and the magnetoacoustic cavity mode. This study supports the possibility of detecting the ionospheric response to the SC by the GPS method. The TEC response to the MI was detected in the auroral latitudes although not on every radio path. The TEC modulation can be associated with the precipitation of superthermal electrons into the lower ionosphere which is undetectable by riometers. The burst in the intensity of the geomagnetically induced currents caused by an interplanetary shock wave turns out to be higher than the currents during the storm’s commencement, although the SC’s amplitude is noticeably lower than the amplitude of the magnetic bay related to the substorm.     

Correlation between the horizontal wind direction and orientation of cross-field anisotropy of small-scale irregularities in the <Emphasis Type="Italic">F</Emphasis> region of midlatitude ionosphere

Radio sounding of midlatitude ionosphere shows that natural small-scale electron density irregularities in the F region are cross-field anisotropic. The orientation of the cross-field anisotropy is different under different geophysical conditions. The cross-field anisotropy orientation is matched with the horizontal wind direction calculated within the HWM07 model for each event. It is ascertained that natural irregularities in a plane perpendicular to the magnetic field are stretched along the horizontal wind direction under different geophysical conditions.     

Influence of precambrian basement on the chemical composition of Mesozoic granitoid rocks in northeastern Asia

A hypothesis for effects of stable tectonic elements on chemical composition of Mesozoic granitoids in northeastern Asia is tested. Chemical compositional change of granitoid rocks is examined in nine-dimensional space of rock-forming oxides. Stable geologic structures of the region are outlined by trends of Euclidean distances between rock recognized as a standard in a space of major rock-forming oxides and composition of individual samples. A data-smoothing polynomial of the fourth order corresponds closely to the geology of the region. Chemically stable masses of quartz diorite are thought to be delivered directly from magmatic sources along deep faults. A great variety of acidic granites, which occupy for each analysis separate cells in the nine-dimensional classification, are presumed to be palingenetic in origin.     

The inhabitants of the spring ice,under-ice water,and sediments of the white sea in the estuarine zone of the Severnaya Dvina River

The data on the supra-ice snow, ice, under-ice water, and benthic algal flora obtained in 2007–2008 by sampling in the estuary of the Severnaya Dvina River are analyzed. The river ice and under-ice water in the estuarine zone and in the channel part of the Severnaya Dvina differed greatly in the algal flora’s composition. The fresh water species never exceeded 8.6%, while the ice algae composed 90–96% of the total ice inhabitants’ biomass. In the under-ice water, this value did not exceed 58–64%. The bacteria in the ice composed not more than 2.5–10% of the total biomass, while, in the under-ice water, 36–49%. The shares of ciliates (0.04%) and nematodes (0.005–1.6%) in the total biomass were negligible. In the estuarine zone, the ice was inhabited mainly by nematodes (78% of the total biomass), while, in the river, their share decreased to 9%. The contribution of bacteria was 15% in Dvina Bay and increased to 61% in the river. The importance of algae in the snow was minor: 7% of the total biomass in the marine zone and 30% in the river region. High species diversity of the algal flora in the sandy and sandy-silty littoral grounds was revealed. The values of the total biomass of the bottom algal flora (0.38 g C/m²) were only two to three times lower than the values revealed in similar habitats in the summer. The epipelithic forms (0.15 g C/m²) dominated, being represented by 46 species of algae (49%). The shares of epipsammonic (0.12 g C/m²) and planktonic (0.11 g C/m²) species were almost equal to each other: 25 and 22 species, respectively (27 and 24%).     

Quantitative and Production Characteristics of Phytoplankton in the Northern Part of the Weddell Sea in Summer

Oceanology - The spatial distribution of the main parameters of primary productivity is described for the northern part of the Weddell Sea in the Antarctic summer of 2020. The integral...