The detection of coronal mass ejections in the interplanetary medium using scintillation observations

Daily observations of scintillating radio sources obtained from July 2011 through June 2012 on the Big Scanning Antenna of the P.N. Lebedev Physical Institute at 111 MHz using a 16 beams system are analyzed. Variations in the observed scintillation indices are compared with data on solar X-ray flares and geomagnetic disturbances. Comparison of the observed scintillation indices on successive days enables the detection of most propagating disturbances associated with coronal events of class M5.0 and higher.     

New data on Upper Kimmeridgian-Tithonian biostratigraphy and ammonites of the eastern Crimea

Based on ammonites, Upper Kimmeridgian sediments are first established in the Crimean Mountains. The Kimmeridgian-Tithonian boundary recognizable in a continuous section is placed inside the Dvuyakomaya Formation of uniform largely clayey sediments. Assemblages of Kimmeridgian ammonites Lingulaticeras cf. procurvum (Ziegler), Pseudowaagenia gemmellariana Oloriz, Euvirgalithacoceras cf. tantalus (Herbich), Subplanites sp.) and Tithonian forms (?Lingulaticeras efimovi (Rogov), Phylloceras consaguineum Gemmellaro, Oloriziceras cf. schneidi Tavera, and Paraulacosphinctes cf. transitorius (Oppel) are described. A new biostratigraphic scheme proposed for the upper Tithonian-Berriasian of the Crimean Mountains includes the following new biostratigraphic units: the Euvirgalithacoceras cf. tantalus Beds of the upper Kimmeridgian, ?Lingulaticeras efimovi Beds of the lower Tithonian, and Oloriziceras cf. schneidi and Paraulacosphinctes cf. transitorius beds of the upper Tithonian. The middle Tithonian is proposed to consist of the fallauxi and semiforme (presumably) zones. The ammonities found determine the early Kimmeridgian-Berriasian age of the Dvuyakornaya Formation that is most likely in tectonic contact with the underlying Khutoran Formation.     

Petrological-geophysical models of the internal structure of the lithospheric mantle of the Siberian Craton

Based on the simultaneous inversion of unique ultralong-range seismic profiles Craton, Kimberlite, Meteorite, and Rift, sourced by peaceful nuclear and chemical explosions, and petrological and geochemical data on the composition of xenoliths of garnet peridotite and fertile primitive mantle material, the first reconstruction was obtained for the thermal state and density of the lithospheric mantle of the Siberian craton at depths of 100–300 km accounting for the effects of phase transformation, anharmonicity, and anelasticity. The upper mantle beneath Siberia is characterized by significant variations in seismic velocities, relief of seismic boundaries, degree of layering, and distribution of temperature and density. The mapping of the present-day lateral and vertical variations in the thermal state of the mantle showed that temperatures in the central part of the craton at depths of 100–200 km are somewhat lower than those at the periphery and 300–400°C lower than the mean temperature of tectonically younger mantle surrounding the craton. The temperature profiles derived from the seismic models lie between the 32.5 and 35 mW/m² conductive geotherms, and the mantle heat flow was estimated as 11–17 mW/m². The depth of the base of the cratonic thermal lithosphere (thermal boundary layer) is close to the 1450 ± 100°C isotherm at 300 ± 30 km, which is consistent with published heat flow, thermobarometry, and seismic tomography data. It was shown that the density distribution in the Siberian cratonic mantle cannot be described by a single homogeneous composition, either depleted or enriched. In addition to thermal anomalies, the mantle density heterogeneities must be related to variations in chemical composition with depth. This implies significant fertilization at depths greater than 180–200 km and is compatible with the existence of chemical stratification in the lithospheric mantle of the craton. In the asthenosphere-lithosphere transition zone, the craton root material is not very different in chemical composition, thermal regime, and density from the underlying asthenosphere. It was shown that minor variations in the chemical composition of the cratonic mantle and position of chemical (petrological) boundaries and the lithosphere-asthenosphere boundary cannot be reliably determined from the interpretation of seismic velocity models only.     

The electron density in clouds of turbulent interstellar plasma

The dependence of the emission measure on the dispersion measure due to the Galactic background has been derived for 120 directions in the Galaxy. This analysis has yielded the mean electron density, effective thickness of the electron layer, and the volume filling factor of the clouds of ionized gas along the line of sight. The pulsar J1745?2900, which lies in a direction close to the direction toward the center of the Galaxy, is located at least 100 pc closer to the observer than the source Sgr A* along the line of sight. The scatter-broadened angular size of J1745?2900 is determined by the turbulent medium in the Sagittarius Arm.     

The magnetic-field structure in a stationary accretion disk

The magnetic-field structure in regions of stationary, planar accretion disks around active galactic nuclei where general-relativistic effects can be neglected (from 10 to 200 gravitational radii) is considered. It is assumed that the magnetic field in the outer edges of the disk, which forms in the magnetosphere of the central black hole during the creation of the relativisitic jets, corresponds to the field of a magnetic dipole perpendicular to the plane of the disk. In this case, the azimuthal field component B_φ in the disk arises due to the presence of the radial field B_ρ and the azimuthal velocity component U_φ. The value of the magnetic field at the inner radius of the disk is taken to correspond to the solution of the induction equation in a diffusion approximation. Numerical solutions of the induction equation are given for a number of cases.     

Quaternary sediments in the axial zone of the Brazil Basin

Lithological and micropaleontological studies of sediments were carried out along the meridional profile across the Brazil Basin. Based on nannoplankton and diatom assemblages, the sediments represented by oxidized miopelagic clays, differently reduced hemipelagic clays, and clayey-siliceous (Ethmodiscus) and calcareous (coccolith-foraminiferal) oozes are attributed to the Pleistocene-Holocene. Specific features of sedimentary material indicate its redeposition by Antarctic bottom waters, mudflows, slumps, and rockslides. It is shown that sedimentation in the Brazil Basin corresponds to the incomplete pelagic (miopelagic) type of oceanic lithogenesis transitional to the near-continental one.     

Pb-Pb age and Sr isotopic characteristic of the Middle Riphean phosphorite concretions: The Zigaza-Komarovo Formation of the South Urals

The Pb-Pb age of phosphorite concretions of the Zigaza-Komarovo Formation, which composes the intermediate horizons of the Riphean stratotype of the South Urals, was determined in fractions resulting from the stepwise dissolution of concretions in 0.1 N, 0.5 N, and 1 N HCl. The determination of the Sr isotopic composition in phosphate fractions was favorable for rejection the fractions polluted with extraneous material. On the ²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb diagram, the isochron based on 31 points corresponds to 1330 ± 20 Ma (MSWD = 1.12), which is in agreement with the stratigraphic position of the Zigaza-Komarovo Formation. The decreased μ₂ value of 9.57 for the phosphorite concretions relative to that of the average earthly lead based on the Stacey-Kramers model (9.74) is related to the rocks with an admixture of mantle lead, which occur in the run-off area of the Zigaza-Komarovo sediments.     

Micromechanical assessment of an internal stability criterion

The internal stability of a soil is a measure of its susceptibility to suffusion and suffosion, two forms of internal erosion. The internal stability of granular filters must be carefully considered when designing new embankment dams and assessing the risk associated with existing embankment dams. Current guidelines for assessing the internal stability of such filters were empirically derived from macroscale observations and consider the shape of the particle-size distribution curve. These guidelines lack a fundamental, scientific micromechanical basis. The initiation and propagation of internal erosion is clearly a particle-scale phenomenon, and this paper applies particulate mechanics to provide a micromechanical justification for one currently used stability criterion. The study used discrete element simulations of idealised virtual soil samples that had various degrees of internal stability when assessed using the criterion proposed by Kézdi [10]. The internal topologies of stable and unstable samples were analysed by considering the distributions of inter-particle contact forces, the number of particle–particle contacts and the average particle stresses. Clear correlations are observed between the filter stability criterion and the average number of contacts per particle and the probability that a given particle participates in stress transmission. The phenomenon of a critical fines content, at which the existing guidelines are no longer considered to be valid, is also considered.     

Pliocene ignimbrites of the Elbrus area in the Neogene-Quaternary volcanism history within the Greater Caucasus (isotope-geochronological data)

Doklady Earth Sciences -     

The Varre-Sai chondrite,a Brazilian fall: petrology and geochemistry

The Varre-Sai meteorite fell along the border of the states of Espirito Santo and Rio de Janeiro, Brazil; on 19 June 2010 at 5:40 pm. Petrography and X-ray powder diffraction (XRD) indicate that the rock is an L5 S4 chondrite, with blastoporphyritic texture that has not been previously described. Geochemical data based on major and rare-earth elements (REEs) show that Varre-Sai is highly similar to the other L chondrites. In Harker diagrams, Varre-Sai, L, and LL chondrites form a single group, suggesting no significant chemical differences between them and contributing to the long-standing debate of whether LL chondrites form a distinct group or whether they are a subset of the L group. Harker diagrams also define a trend from E to H and L/LL chondrites, similar to the cosmochemical trends suggested by other authors. The behaviour of Fe₂O_3t and NiO indicates a relationship with Fe-Ni alloys, and their trend in the diagram suggests some chemical differentiation in the ordinary chondrite parental bodies. The REE content in Varre-Sai, normalized to C chondrites, falls in the field of L chondrites and others, but with slight REE enrichment. The chemical differences in chondrites, mainly in REEs, Fe₂O_3t and NiO could be alternatively interpreted as variations in the inherited agglutinated materials as chondrules, Ca–Al-rich inclusions and Fe–Ni nodules.