High-pressure rocks in the serpentinite melange of the Chara zone,Eastern Kazakhstan: Geochemistry,petrology, and age

The nature of the protolith of high-pressure rocks occurring as exotic blocks in serpentinite melange in the Chara ophiolite belt, Eastern Kazakhstan, is identified based on petrological and geochemical evidence. The distribution of incompatible HFSE in these rocks suggests that their protoliths were similar to E- and N-MORB tholeiites and, more rarely, to OIB alkaline basalts. This testifies to the activity of plume magmatism in the Early Paleozoic evolution of the Paleoasian Ocean. The Ar-Ar ages of phengite and Na-amphibole from the rocks date the subduction/exhumation of high-pressure rocks in the Chara ophiolite belt at the Late Ordovician (450 ± 5 Ma).     

Typification and the Current State of Baikal Lake Shore

Water Resources - The major shore-forming factors typical of Lake Baikal, the main types and subtypes of lake shore, and their current state are considered. The complex geological structure has...     

Modeling radiative forcing by background aerosol on the basis of measurement data

The solar radiation flux incident on the land surface and aerosol radiative forcing are calculated from measurements carried out under clear skies during the summers of 2004 and 2005 at the Zvenigorod Scientific Station (ZSS) of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. In these calculations, the following five models of aerosol optical parameters are used: a standard model of continental aerosol, a semiempirical model based on measurement data, and three models obtained from calculations on the basis of the Mie scattering theory for the mean size distribution of aerosol particles (which is retrieved from aureole measurements). A study of the sensitivity of the flux and forcing to the choice of aerosol model has shown that the relative error related to the model choice is not large (<5%) for the incident radiation flux and reaches 120% for aerosol forcing at the atmospheric upper boundary. The aerosol radiative forcing at the atmospheric upper boundary is also estimated and, according to our calculations, varies from −15 to −2 W/m². The use (in calculations) of the values of the albedo of single-scattering and the factor of scattering-indicatrix asymmetry at a wavelength of 550 nm, which were obtained for each of the observation periods, has made it possible to significantly refine the value of aerosol radiative forcing (compared to that calculated for the means of these parameters over all the periods). An even more accurate determination of aerosol radiative forcing is possible only when data on the size-distribution of aerosol particles and their chemical composition for a certain situation under analysis are available. As a result of this study, two models of the optical parameters of background aerosol have been proposed for use in radiation calculations: a semiempirical model and a mean model obtained from the calculations based on the theory of scattering. Both models use the values of the albedo of single scattering and the factor of asymmetry (at a wavelength of 550 nm) retrieved from the measurements for each of the observation periods.     

Seasonal and daily cycles of surface ozone in the extratropical latitudes

Major characteristics are considered of the time dependence of the surface-ozone mixing ratio obtained at a number of stations of the world network, which transmit observational data to the World Data Centre for Greenhouse Gases and to the databank of the European Monitoring and Evaluation Program for long-range transport of air pollution. The 1990–2004 data, obtained mainly in the Northern Hemisphere, are analyzed. The seasonal cycle of surface ozone is clearly defined at all 114 observation sites under consideration, and its daily cycle is also pronounced at all stations except for the polar ones. Six basic types of seasonal and daily variations in surface ozone are revealed with the use of cluster analysis. In addition to quantitative characteristics, these types are distinguished by the forms of seasonal and daily cycles (in particular, by the presence of one or two seasonal maxima and by the time of maximum occurrence). Six groups of stations are classified according to these differences: remote (unpolluted), lowland slightly polluted, lowland polluted, upland slightly polluted, mountain, and polar/remote coastal stations. For the group of remote stations in the Northern Hemisphere, the seasonal maximum of surface ozone occurs in April in the daytime and at night. For the group of polluted stations (including most of the European rural stations), whose observational data are characterized by two seasonal maxima (in spring and in summer) or one broad spring-summer maximum, the spring maximum is observed in the daytime and at night, and the summer maximum is observed only in the daytime. It is concluded that spring maximum is caused mainly by dynamic processes—air-mass transport—and the amplitude of the summer maximum is determined by photochemical generation of ozone.     

Determining the Physical Parameters of the System V1413 Aql in Its Quiescent and Active States in 20122017

We present the results of our spectroscopic observations for the classical symbiotic star V1413 Aql in 20122017. In this period the system was in both active and rare (for it) quiescent states. In 2012 the optical spectrum was dominated by the radiation from the erupted hot component of spectral type F47 III. In 2017 the system passed to a quiescent state that lasted at least three months. In this period lines of ions with high ionization potentials, such as He II 4686 Å and CIV 5802 Å, appeared in the spectrum. The temperature and luminosity of the hot component in this period were $$T_{\textrm{hot}}\approx 90\,000$$ K and $$L_{\textrm{hot}}\approx 1800L_{\odot}$$. We show that the quiescent state in 2017 differs little in its time and energy characteristics from the previous active state observed in 1993.     

The Results of Verification of Data Obtained from TerraSAR-X Spacecraft Using Ground Test Facilities

Izvestiya, Atmospheric and Oceanic Physics - In this paper, the experience of interaction of different organizations within the implementation of the technique of validation of the onboard...     

Spectroscopic monitoring of the recurrent nova RS Oph after its outburst in 2006

We analyze low-dispersion (1.8 Å per pixel) spectra of the recurrent nova RS Oph taken between the 10th and 241st days after its outburst on February 12, 2006. The spectra exhibit various stages in the development of the outburst, from its coronal phase to its nebular phase. We identified about 200 spectral lines at 3700–7500 Å, and fluxes were determined for the strongest lines. The spectral behavior of this outburst does not differ strongly from the previous one. One of the main differences is the presence of flux variations in the forbidden [NII] 5775 Å, [OI] 6300 Å, [OIII] 4959 Å, [OIII] 5007 Å, [KIV] 6101 Å, [FeVII] 6086 Å, and [FeX] 6375 Å lines, as well as in the HeI 5876 Å, HeI 6678 Å, HeII 4686 Å lines. We also obtained high-dispersion (0.06 Å per pixel) spectra in the region of the Hα and HeI 5876 Å lines between the 9th and 113th days after the outburst. The HeI 5876 Å profile has three components. This shape of the profile may result from the formation of an envelope after the aspherical explosion.     

Structure and chemical composition of the envelope of Nova V339 del in the nebular phase

Based on our spectrophotometric observations, we have investigated the envelope of Nova V339 Del in the nebular phase. Our modeling of the Hα line profiles and their comparison with the observed profiles have shown that the Nova envelope consists of circumpolar ejecta and a disk-shaped central component. The inclination of the orbital plane of the binary system, 65°, has been determined in the same way. We have estimated the mean electron density to be ~10⁶ cm^-3. Our estimates of the abundances of some chemical elements in the Nova envelope have shown that the concentrations of helium, neon, and iron are nearly solar, while the concentrations of nitrogen and oxygen exceed the solar ones by a factor of 120 ± 60 and 8 ± 1.6, respectively. The mass of the emission envelope in the nebular phase (from 253 to 382 days after the brightness maximum) has been estimated to be ~7 × 10^-5 M _⊙.     

Spectral evolution of the classical symbiotic star V1413 Aql during a new activity cycle

We present the results of our spectroscopic observations for the classical symbiotic star V1413 Aql performed in 2008–2011. Various states of the hot component are considered: almost quiescence in 2008, very slow outburst onset in 2009, outburst maximum in 2010, and gradual brightness decline in the erupted hot component in 2011. We have established that, according to a spectroscopic criterion, in 2008 the system was in quiescence. We have shown that the parameters of the hot component during its outburst can be determined only by modeling the differences of the spectra taken at different eclipse phases. The active hot component of V1413 Aql at the outburst maximum is shown to have had the record late (for a symbiotic star) spectral type K2. At various stages of the new activity cycle, we have modeled the continuumenergy distribution based on a standard three-componentmodel, a model including a standard accretion disk and a red giant, and amodel including a supergiant (of various spectral types) and a red giant. The parameters of the system’s components have been determined.