On the theory of a steady circulation in a baroclinic ocean

Some results are presented of numerical experiments associated with calculations of stationary fields of current velocity and temperature in the ocean. Results obtained by two different approaches to the theory of ocean circulation are compared: without regard for horizontal exchange under conditions of bottom sticking and with due regard for horizontal exchange in case of bottom slipping.     

The Mid-Paleozoic and Mid-Triassic Pulses of Trap Magmatism in the East of the Siberian Platform: Evidence from the First 40Ar/39Ar Isotope Dating of Dolerite Sills

Doklady Earth Sciences - The paper presents the results from the first 40Ar/39Ar isotope dating of eleven mafic sills recovered by deep boreholes in the eastern Siberian Platform. Most of the dates...     

Age of the Chibit Glaciation in Gornyi Altai

Doklady Earth Sciences - New results of Optically-Stimulated Luminescence (OSL) dating that make it possible to clarify the age of the Chibitskii glaciation in the Altai Mountains are reported....     

Infrared Spectroscopy and Internal Structure of Diamonds from the Ichetyu Placer,Central Timan,Russia

Geology of Ore Deposits - A wide range of model temperature, which is typical for dodecahedroids from placer deposits in the Urals, Brazil, and the northern Yakutia diamond province has been...     

Expulsion of dust from dark-matter halos at high redshifts

The conditions required for the expulsion of dust grains from primordial galaxies (dark-matter halos) are considered. The initial configuration is taken to be a dark-matter halo with the profile of a modified isothermal sphere; the baryons are taken to be in equilibrium with the corresponding virial temperature. The baryon density profile is calculated assuming hydrostatic equilibrium. A star-formation rate corresponding to a star-forming efficiency of 10% is assumed. The dust is transported from the galaxy by the radiation of stars concentrated in the central regions. Due to friction via collisions with gas in central regions, a fairly high luminosity is required in order for the radiation pressure to be strong enough to expel dust from the galaxy—the ratio of the luminosity to the total mass of the galaxy can reach unity.     

Instabilities in the ionization zones around the first stars

We consider the evolution of the ionization zone around Population III stars with M _* ?? 25?C200M _?? in protogalaxies with M ?? 10⁷ M _?? at redshifts z = 12, assuming that the dark-energy profile is a modified isothermal sphere. We study the conditions for the growth of instabilities in the ionization zones. The Rayleigh-Taylor and thermal instabilities develop efficiently in the ionization zones around 25?C40M _?? stars, while this efficiency is lower for stars withM _* ?? 120M _??. For more massive stars (??200M _??), the flux of ionizing photons is strong enough to considerably reduce the gas density in the ionization zone, and the typical lifetimes of stars (??2 Myr) are insufficient for the growth of instabilities. The gas in a protogalaxy with M ?? 10⁷ M _?? with a 200M _?? central star is completely ionized by the end of the star??s lifetime; in the case of a 120M _?? central star, only one-third of the total mass of gas is ionized. Thus, ionizing photons from stars with M _* ? 120M _?? cannot leave protogalaxies with M ? 10⁷ M _??. If the masses of the central stars are 25 and 40M _??, the gas in protogalaxies of this mass remains essentially neutral. We discuss the consequences of the evolution of the ionization zones for the propagation of the envelope after the supernova explosions of the strs and the efficiency of enrichment of the intergalactic medium in heavy elements.     

Impact of the geomagnetic field and solar radiation on climate change

Recent studies have shown that, in addition to the role of solar variability, past climate changes may have been connected with variations in the Earth??s magnetic field elements at various timescales. An analysis of variations in geomagnetic field elements, such as field intensity, reversals, and excursions, allowed us to establish a link between climate changes at various timescales over the last millennia. Of particular interest are sharp changes in the geomagnetic field intensity and short reversals of the magnetic poles (excursions). The beginning and termination of the examined geomagnetic excursions can be attributed to periods of climate change. In this study, we analyzed the possible link between short-term geomagnetic variability (jerks) and climate change, as well as the accelerated drift of the north magnetic pole and surface temperature variations. The results do not rule out the possibility that geomagnetic field variations which modulate the cosmic ray flux could have played a major role in climate change in addition to previously induced by solar radiation.     

Methane Concentration and Emission in Dominant Landscapes of Typical Tundra of Western Yamal

Doklady Earth Sciences - Methane concentration in dominant landscapes of typical tundra of Western Yamal has been measured. The highest methane content in the active layer was measured in tundra...     

Evolution of High-Magnesium Melts During Crystallization of Rocks in Ultramafic Massifs,Siberian Platform

Doklady Earth Sciences - The results of study of primary melt inclusions in accessory Cr–spinelides from dunite have revealed features of the chemical compositions of high-magnesium...     

Permafrost aggradation and methane production in low accumulative laidas (tidal flats) of the Kara Sea

Doklady Earth Sciences - It was established that along with permafrost degradation, the processes of permafrost aggradation occur in the modern low accumulative surfaces of Kara Sea. The cycle of...