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Avanesov G Zhukov B Ziman YA Kostenko V Kuzmin A Murav'ev V Fedotov V Bonev B Mishev D Petkov D Krumov A Simeonov S Boycheva V Uzunov YU Weide GG Halmann D Pössel W Head J Murchie S Schkuratov YuG Berghänel R Danz M Mangoldt T Pihan U Smith B 《Planetary and Space Science》1991,39(1-2):281-295
From February to March 1989 the Phobos 2 spacecraft took 37 TV images of Phobos at a distance of 190-1100 km. These images complement Mariner-9 and Viking data by providing higher-resolution coverage of a large region West of the crater Stickney (40-160 degrees W) and by providing disk-resolved measurements of surface brightness at a greater range of wavelengths and additional phase angles. These images have supported updated mapping and characterization of large craters and grooves, and have provided additional observations of craters' and grooves' bright rims. Variations in surface visible/near-infrared color ratio of almost a factor of 2 have been recognized; these variations appear to be associated with the ejecta of specific large impact craters. Updated determinations of satellite mass and volume allow calculation of a more accurate value of bulk density, 1.90 +/- 0.1 g cm-3. This is significantly lower than the density of meteoritic analogs to Phobos' surface, suggesting a porous interior perhaps containing interstitial ice. 相似文献
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A. Mishev I. Usoskin O. Raukunen M. Paassilta E. Valtonen L. Kocharov R. Vainio 《Solar physics》2018,293(10):136
Using data obtained with neutron monitors and space-borne instruments, we analyzed the second ground-level enhancement (GLE) of Solar Cycle 24, namely the event of 10 September 2017 (GLE 72), and derived the spectral and angular characteristics of associated GLE particles. We employed a new neutron-monitor yield function and a recently proposed model based on an optimization procedure. The method consists of simulating particle propagation in a model magnetosphere in order to derive the cutoff rigidity and neutron-monitor asymptotic directions. Subsequently, the rigidity spectrum and anisotropy of GLE particles are obtained in their dynamical evolution during the event on the basis of an inverse-problem solution. The derived angular distribution and spectra are discussed briefly. 相似文献
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The use of limited global information in multiscale simulations is needed when there is no scale separation. Previous approaches entail fine-scale simulations in the computation of the global information. The computation of the global information is expensive. In this paper, we propose the use of approximate global information based on partial upscaling. A requirement for partial homogenization is to capture long-range (non-local) effects present in the fine-scale solution, while homogenizing some of the smallest scales. The local information at these smallest scales is captured in the computation of basis functions. Thus, the proposed approach allows us to avoid the computations at the scales that can be homogenized. This results in coarser problems for the computation of global fields. We analyze the convergence of the proposed method. Mathematical formalism is introduced, which allows estimating the errors due to small scales that are homogenized. The proposed method is applied to simulate two-phase flows in heterogeneous porous media. Numerical results are presented for various permeability fields, including those generated using two-point correlation functions and channelized permeability fields from the SPE Comparative Project (Christie and Blunt, SPE Reserv Evalu Eng 4:308–317, 2001). We consider simple cases where one can identify the scales that can be homogenized. For more general cases, we suggest the use of upscaling on the coarse grid with the size smaller than the target coarse grid where multiscale basis functions are constructed. This intermediate coarse grid renders a partially upscaled solution that contains essential non-local information. Numerical examples demonstrate that the use of approximate global information provides better accuracy than purely local multiscale methods. 相似文献
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Ilya D. Mishev 《Computational Geosciences》2002,6(3-4):253-268
We extend and generalize recently proposed finite volume methods using the framework of mixed finite element methods. Proposed discretizations are defined for tensor permeabilities and naturally produce a generalization of harmonic averaging, and are therefore well suited for heterogeneous and anisotropic media. They are locally mass conservative and work on extremely flexible distorted meshes. Flux variables can be excluded locally and the resulting discretizations for the pressures has the same stencils for Voronoi/PEBI grids as 2-point finite volume discretizations currently used in many simulators. 相似文献
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A.L. Mishev 《Journal of Atmospheric and Solar》2010,72(16):1195-1199
The cause of the correlation between cloud cover and cosmic ray intensity is still a subject of discussion. The atmospheric transparency is the primary signature of the atmospheric state. The ability to use neutron monitor and Cherenkov telescope data in order to study atmospheric processes is demonstrated. The recently designed lead free neutron monitor at the Basic Environmental Observatory Moussala (42.11N, 23.35E, 2925 m a.s.l.) is described. The possibility to use Cherenkov telescope measurements for estimation of atmospheric transparency is demonstrated on the basis of Monte Carlo simulations and experimental data. The Monte Carlo simulations are carried out with CORSIKA code assuming FLUKA and QGSJET II hadron interaction models. Experimental data from Cherenkov telescope are presented. Several physical mechanisms related to the influence of cosmic rays on the cloud cover, respectively, the atmospheric transparency are widely discussed. 相似文献
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The longitudinal profile of atmospheric cascades is sensitive to the energy, mass of the primary particle and to atmospheric state. In this work are compared ionization yield functions Y for winter, summer and US standard profiles of Earth's atmosphere. The various profiles are obtained on the basis of CORSIKA 6.52 code simulations using FLUKA 2006 and QGSJET II hadronic interaction subroutines. The energy deposit of proton induced cascade processes in the atmosphere is calculated for different types of atmospheres. The ion pair production in the atmosphere and the contribution of the different shower components, precisely the electromagnetic, muon and hadronic is estimated according applied atmospheric types. In addition simulations with different hadronic interaction models GHEISHA 2002, FLUKA 2006 and QGSJET II are carried out. The ion pair production in the atmosphere and the contribution of different shower components is estimated according the assumed hadronic interaction models. The yield function Y for total ionization, respectively, for the different components is compared. The observed differences are widely discussed. General conclusion concerning the application of various atmospheric profiles and hadron interaction models is carried out. 相似文献
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