Polarimetry of comets: A review     

Dobrovolsky  O. V.  Kiselev  N. N.  Chernova  G. P. 《Earth, Moon, and Planets》1986,34(2):189-200

Some attempts of polarimetric sounding of Comet Halley will be undertaken from the flyby probes. In order to facilitate the final planning and the future interpretation of these experiments we have done a thorough analysis of practically all available polarimetric observations. An emphasis is made on interpretation attempts and their discussion. The results of the phase dependence of polarization investigations are presented covering a wide range of phase angles . The chief peculiarities of this dependence are: maximum polarization at = 90, diminishing through zero at 20, negative values up to several per cent and a final growth to zero at zero . A division into gaseous and dusty comets on polarimetric basis is revealed. The wavelength dependence of polarization is discussed. The numerous results of detailed polarimetry are compared to the negative results of attempts to detect the elliptical polarization. New observational problems arising from the evidence given by the negative polarization at small phase angles and by the opposition effect recently discovered are discussed.  相似文献   

Photochemical models of the atmosphere and their application in ozonosphere and climate studies: A review     

I. L. Karol’  A. A. Kiselev 《Izvestiya Atmospheric and Oceanic Physics》2006,42(1):1-31

This review is devoted to problems in the photochemical modeling of atmospheric processes. The physicochemical and mathematical foundations underlying the construction of photochemical models are described, a classification of the atmospheric reactions is presented, and the features of photochemical modeling are considered under various irradiance conditions for various atmospheric layers and geographical regions. Atmospheric processes that are important to photochemical models are discussed. Applications involving photochemical models are outlined. Some results are presented to illustrate the capabilities of photochemical models. Special attention is given to relatively recent directions in photochemical modeling, such as data assimilation and inverse problems. The review can be used by experts in areas related to atmospheric chemistry as a basic source of knowledge on the subject and for the development of photochemical modules for atmospheric models.  相似文献   

Statistical analysis of a global photochemical model of the atmosphere     

V. A. Frol’kis  I. L. Karol’  A. A. Kiselev  Yu. E. Ozolin  V. A. Zubov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(4):413-422

This is a study of the sensitivity of model results (atmospheric content of main gas constituents and radiative characteristics of the atmosphere) to errors in emissions of a number of atmospheric gaseous pollutants. Groups of the model variables most dependent on these errors are selected. Two variants of emissions are considered: one without their evolution and the other with their variation according to the IPCC scenario. The estimates are made on the basis of standard statistical methods for the results obtained with the detailed onedimensional radiative—photochemical model of the Main Geophysical Observatory (MGO). Some approaches to such estimations with models of higher complexity and to the solution of the inverse problem (i.e., the estimation of the necessary accuracy of external model parameters for obtaining the given accuracy of model results) are outlined.  相似文献   

CCD Polarimetry of Near-Earth Asteroid 2014 JO25 and Comet 41P/Tuttle–Giacobini–Kresák at the Prime Focus of the 2.6-m Shajn Telescope of the Crimean Astrophysical Observatory     

Rumyantsev  V. V.  Kiselev  N. N.  Ivanova  A. V. 《Solar System Research》2019,53(2):91-97

The results of the first polarimetric measurements of near-Earth asteroid 2014 JO₂₅ and comet 41P/Tuttle-Giacobini-Kresák performed on April 19, 2017, with a CCD sensor at the prime focus (f/3.85) of the 2.6-m Shajn Telescope of the Crimean Astrophysical Observatory in the R filter are reported. The degree of linear polarization of the asteroid is P = 2.69 ± 0.44% at a phase angle of 55.6°, which is typical of an S-type asteroid. Its geometric albedo is ρ_v ≈ 0.2. A digital filter applied to the direct image of the comet reveals a jet and a tail directed toward the Sun (PA = 45.1°) and away from it (PA = 241.2°), respectively, in the coma. The maximum degree of linear polarization in the near-nucleus region of the comet is 18% at a phase angle of 69.8°. The polarization decreases to 16.2–10.7% in coma regions with a radius of 865–4856 km. Various factors affecting the maximum degree of polarization and the polarization-degree distribution over the coma are discussed.

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Verification of the multi-chamber model of radioactivity migration in reservoirs     

A. L. Krylov  A. V. Nosov  V. P. Kiselev 《Russian Meteorology and Hydrology》2016,41(5):344-350

A multi-chamber model of radioactivity migration in reservoirs was developed. It describes transport of radioactive substances in water and in bed sediments taking into account sorbtion of radionuclides on suspended particles. The model provides higher resolution than simplified chamber models do. At the same time, unlike complex two- or three-dimensional dynamic models, it does not require hard-to-obtain data such as detailed data on bathymetry, currents and winds. The model was included into the Sybilla program code that was developed in the framework of the Rosatom project called PRORYV. The model was verified against the observed data on the contamination of the Kiev Reservoir with ¹³⁷Cs in 1986.  相似文献   

An astrometric study of the triple star ADS 48     

O. V. Kiyaeva  A. A. Kiselev  E. V. Polyakov  V. B. Rafal’skii 《Astronomy Letters》2001,27(6):391-397

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A Negative Branch of Polarization for Comets and Atmosphereless Celestial Bodies and the Light Scattering by Aggregate Particles     

Petrova  E. V.  Jockers  K.  Kiselev  N. N. 《Solar System Research》2001,35(5):390-399

Optical observations of comets and atmosphereless celestial bodies show that a change of sign of the linear polarization of scattered light from negative to positive at phase angles less than 20° is typical of the cometary coma, as well as of the regolith of Mercury, the Moon, planetary satellites, and asteroids. To explain a negative branch of polarization, this research suggests a unified approach to the treatment of cometary-dust particles and regolith grains as aggregate forms. A composite structure of aggregate particles resulting in the interaction of composing structural elements (monomers) in the light-scattering process is responsible for the negative polarization at small phase angles, if the monomer sizes are comparable to the wavelength. The characteristics of single scattering of light calculated for aggregates of this kind turned out to be close to the properties observed for cometary dust. Unlike the cometary coma, the regolith is an optically semi-infinite medium, where the interaction between particles is significant. To find the reflectance characteristics of regolith, the radiative-transfer equation should be solved for a regolith layer. In this case, the interaction between scatterers can be modeled to a certain extent by representing the regolith grains as aggregate structures consisting of several or many elements. Although real regolith grains are much larger than the particles considered here, laboratory measurements have shown that it is precisely the surface irregularities comparable to the wavelength that cause a negative branch of polarization. The main observed features of the phase and spectral dependence of the linear polarization of light scattered from comets and atmosphereless celestial bodies, which are due to the difference of the elementary scatterers in composition, size, and structure, can be successfully explained using the aggregate model of particles.  相似文献   

Upper mantle beneath foothills of the western Himalaya: subducted lithospheric slab or a keel of the Indian shield?   总被引：1，自引：0，他引：1  

L. Vinnik  A. Singh  S. Kiselev  M. Ravi Kumar 《Geophysical Journal International》2007,171(3):1162-1171

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Composition and sources of Devonian volcanism in the Vilyui rift     

A. I. Kiselev  V. V. Yarmolyuk  A. V. Nikiforov  K. N. Egorov 《Doklady Earth Sciences》2007,415(5):744-750

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Petrochemistry of Cenozoic basalts and associated rocks in the Baikal rift zone   总被引：1，自引：0，他引：1  

A.I. Kiselev  H.A. Golovko  M.E. Medvedev 《Tectonophysics》1978,45(1):49-59

The main episode of Cenozoic volcanic activity occurred simultaneously with formation of the Sayan—Baikal uplift, before the rift depressions were initiated. Volcanism and rifting in this region have developed as independent processes, connected with each other only by an ultimate primary mantle energy source. The volcanic regions do not coincide with the rift depressions, except in the Tunka graben.Chemical features of the volcanics show that during the entire period of volcanic activity there was a complex alternation of basaltic lavas of alkaline, intermediate and tholeiitic composition. Both alkaline and subalkaline lavas are distributed over the entire volcanic region, excepting the Tunka depression where tholeiitic lavas are predominant. However, there is neither mineralogical nor chemical evidence for the existence of two separate magma types within the Baikal rift zone.Judging by the presence of high-pressure, lherzolitic megacrysts of clinopyroxene, and to a lesser extent titaniferous biotite and amphibole in alkaline basalts, variations of lava chemistry are connected with high-pressure fractionation of initial melts, which was more complete for sources outside the rift zone. The predominance of tholeiitic lavas in the Tunka depression is likely to have been caused by a higher degree of partial melting and quick ascent of magma to the surface, facilitated by a high geothermal gradient under the depression where crustal extension is taking place.  相似文献