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61.
We consider the reflection of non-polarized radiation from the point-like sources above the accretion discs both the optically thick and optically thin. We investigate the dependence of the polarization of reflected radiation on the aperture angle of incident radiation. The aperture angle is determined by the radius of accretion disc and the height of the source above the disc. For optically thick accretion discs we show that, if the aperture angle is smaller 70 grad, then the wave electric field oscillations of reflected radiation are parallel to the accretion disc plane. For aperture angle greater than 70 grad the electric field oscillations are parallel to the plane “normal to accretion disc—the line of sight”. The latter also holds for reflection from the optically thin accretion disc independent of the aperture angle value. 相似文献
62.
Results of the experimental study of ion exchange properties of deep-sea pelagic sediments and related ferromanganese nodules (FMN) are considered. The exchange complex of sediments and nodules includes Na+, K+, Ca2+, and Mg2+ cations. The FMNs also include Mn2+ cations. Series of reactivity of metal cations during exchange reactions in different types of pelagic clayey sediments and diagenetic-sedimentary FMN are compiled. Series of exchange capacity of the sediments and FMN for alkali and heavy metal cations are also presented. The exchange capacity of FMN is always higher than that of enclosing sediments. Sediments are characterized by reversible equivalent sorption of cations of both alkali and heavy metals. Irrespective of the mineral composition, the FMNs are characterized by the reversible equivalent sorption of alkali metal cations, whereas sorption of heavy metal cations is only partly reversible. More over, alkali metal cations do not replace heavy metal cations. The results obtained refine the role of ion exchange processes in the redistribution of heavy metal cations at the water-bottom sediment interface during the diagenetic-sedimentary formation of ferromanganese nodules. 相似文献
63.
64.
R. A. Burenin O. V. Terekhov R. A. Sunyaev A. V. D’yachkov G. Khavenson B. S. Novikov I. D. Tserenin K. M. Sukhanov P. Goldoni A. Claret A. Goldwurm J. Paul F. Pelaez E. Jourdain J. -P. Roques G. Vedrenne 《Astronomy Letters》2000,26(7):413-422
We present the observations of cosmic gamma-ray bursts (GRBs) with the main detector of the SIGMA telescope onboard the Granat Observatory from January 1990 through September 1994. The observations were carried out in the energy range 35–1300 keV. We detected 36 GRBs and 31 high-energy solar flares during this period. No GRB fell within the main field of view; they were all recorded by the “secondary optics” of the telescope. The SIGMA telescope recorded relatively bright bursts with peak fluxes of 10?6–10?4 erg s?1 cm?2 in the 100–500-keV energy band. Stable detector background allows the long-term variability of GRB sources on a time scale of ~1000 s to be studied. The results of our search for early afterglows of GRBs are presented. The flux averaged over all bursts in the interval 100–800 s after the main event is 0.36±0.14 counts s?(35–300 keV), suggesting that there is soft gamma-ray emission on this time scale after a considerable number of GRBs. 相似文献
65.
66.
M. N. Pavlinsky S. A. Grebenev P. A. Mazov I. A. Dekhanov D. B. Ryvkin R. A. Sunyaev V. I. Surtaev N. V. Mokrousov A. G. Glushenko S. I. Yampol’skii A. D. Novikov 《Astronomy Letters》2000,26(12):779-787
The Spin-X wide-field X-ray monitor of the Spectrum-X-Gamma astrophysical observatory, which is based on the principle of a coded-aperture telescope, is designed to detect and localize cosmic gammaray-burst (GRB) sources; to survey large areas of the sky in search of new transients; and to carry out long-term observations of bright Galactic sources, including X-ray bursters. The monitor consists of two noncoaxial identical modules, Spin-X1 and Spin-X2, which together cover 6.8% of the sky. The high-apogee, four-day orbit of the Spectrum-XG satellite allows the instrument to be in observing mode more than 50% of the time. Having simulated the rate of GRB detection by Spin-X, we show that extrapolating BATSE 50–300-keV average data on the number of GRBs, their duration, and their mean energy spectrum to the X-ray energy band leads to disagreement with the observed detection rate of GRBs in the X-ray band. The number of GRBs that can be detected and localized with an accuracy r≤3′ (3σ) (the error-circle radius) by Spin-X is estimated to be ten bursts per year. We present data on the Spin-X sensitivity achievable during long-term observations of persistent and transient sources and on its sensitivity to X-ray bursts from Galactic sources in the 2–30-keV energy band. 相似文献
67.
N. O. Sorokhtin L. I. Lobkovsky N. E. Kozlov N. G. Novikov S. L. Nikiforov O. Yu. Bogdanova 《Doklady Earth Sciences》2015,465(2):1229-1232
The perspectives of development of the Varanger–Timan petroleum basin are considered. The Varanger–Timan oil-and-gas basin was formed in the Riphean and Vendian on the passive continental margin of the East European Plate. Evolution of the Barents–Kara region in the Mesoproterozoic and Neoproterozoic led to a mosaic junction of the lithospheric plates having different ages and having undergone significant alterations during the Caledonian and Variscan orogenies. The spatiotemporal regularities of the interaction between geodynamic processes and conditions providing for the formation of conventional and unconventional hydrocarbon fields are described. 相似文献
68.
Agnes Mazot Dmitri Rouwet Yuri Taran Salvatore Inguaggiato Nick Varley 《Bulletin of Volcanology》2011,73(4):423-441
During 2007–2008, three CO2 flux surveys were performed on El Chichón volcanic lake, Chiapas, Mexico, with an additional survey in April 2008 covering
the entire crater floor (including the lake). The mean CO2 flux calculated by sequential Gaussian simulation from the lake was 1,190 (March 2007), 730 (December 2007) and 1,134 g m−2 day−1 (April 2008) with total emission rates of 164 ± 9.5 (March 2007), 59 ± 2.5 (December 2007) and 109 ± 6.6 t day−1 (April 2008). The mean CO2 flux estimated from the entire crater floor area was 1,102 g m−2 day−1 for April 2008 with a total emission rate of 144 ± 5.9 t day−1. Significant change in CO2 flux was not detected during the period of survey, and the mapping of the CO2 flux highlighted lineaments reflecting the main local and regional tectonic patterns. The 3He/4He ratio (as high as 8.1 R
A) for gases in the El Chichón crater is generally higher than those observed at the neighbouring Transmexican Volcanic Belt
and the Central American Volcanic Arc. The CO2/3He ratios for the high 3He/4He gases tend to have the MORB-like values (1.41 × 109), and the CO2/3He ratios for the lower 3He/4He gases fall within the range for the arc-type gases. The high 3He/4He ratios, the MORB-like CO2/3He ratios for the high 3He/4He gases and high proportion of MORB-CO2 (M = 25 ±15%) at El Chichón indicate a greater depth for the generation of magma when compared to typical arc volcanoes. 相似文献
69.
Salvatore Inguaggiato Fabio Vita Dmitri Rouwet Nicole Bobrowski Sabina Morici Aldo Sollami 《Bulletin of Volcanology》2011,73(4):443-456
On 27 February 2007, a new eruption occurred on Stromboli which lasted until 2 April. It was characterized by effusive activity
on the Sciara del Fuoco and by a paroxysmal event (15 March). This crisis represented an opportunity for us to refine the
model that had been developed previously (2002–2003 eruption) and to improve our understanding of the relationship between
the magmatic dynamics of the volcano and the geochemical variations in the fluids. In particular, the evaluation of the dynamic
equilibrium between the volatiles (CO2 and SO2) released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of
criticality of the volcanic activity. One of the major accomplishments of this study is a 4-year database of summit soil CO2 flux on the basis of which we define the thresholds (low–medium–high) for this parameter that are empirically based on the
natural volcanological evolution of Stromboli. The SO2 fluxes of the degassing plume and the CO2 fluxes emitted from the soil at Pizzo Sopra la Fossa are also presented. It is noteworthy that geochemical signals of volcanic
unrest have been clearly identified before, during and after the effusive activity. These signals were found almost simultaneously
in the degassing plume (SO2 flux) and in soil degassing (CO2 flux) at the summit, although the two degassing processes are shown to be clearly different. The interpretation of the results
will be useful for future volcanic surveillance at Stromboli. 相似文献
70.
We suggest a two-step mechanism for the generation of the parallel electric field at the Alfvén wave. At the first step, the coupling with the compressional mode due to the magnetic field non-uniformity and finite plasma pressure provides the parallel magnetic field of Alfvén wave. At the second step, the compressional mode acquires the parallel electric field due to coupling with the electrostatic mode as required by the quasi-neutrality condition in kinetics. The parallel electric field acquired by the Alfvén mode is considerably larger than that due to the single-step coupling between the Alfvén and electrostatic modes in kinetics. 相似文献