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排序方式: 共有98条查询结果,搜索用时 15 毫秒
31.
D. V. Bisikalo P. V. Kaigorodov D. E. Ionov V. I. Shematovich 《Astronomy Reports》2013,57(10):715-725
As a rule, the orbital velocities of “hot Jupiters,” i.e., exoplanets with masses comparable to the mass of Jupiter and orbital semi-major axes less than 0.1 AU, are supersonic relative to the stellar wind, resulting in the formation of a bow shock. Gas-dynamical modeling shows that the gaseous envelopes around hot Jupiters can belong to two classes, depending on the position of the collision point. if the collision point is inside the Roche lobe of the planet, the envelopes have the almost spherical shapes of classical atmospheres, slightly distorted by the influence of the star and interactions with the stellar-wind gas; if the collision point is located outside the Roche lobe, outflows from the vicinity of the Lagrangian points L1 and L2 arise, and the envelope becomes substantially asymmetrical. The latter class of objects can also be divided into two types. If the dynamical pressure of the stellar-wind gas is high enough to stop the most powerful outflow from the vicinity of the inner Lagrangian point L1, a closed quasi-spherical envelope with a complex shape forms in the system. If the wind is unable to stop the outflow from L1, an open aspherical envelope forms. The possible existence of atmospheres of these three types is confirmed by 3D numerical modeling. Using the typical hot Jupiter HD 209458b as an example, it is shown that all three types of atmospheres could exist within the range of estimated parameters of this planet. Since different types of envelopes have different observational manifestations, determining the type of envelope in HD 209458b could apply additional constrains on the parameters of this exoplanet. 相似文献
32.
Pavel N. Mager Dmitri Yu. Klimushkin Nickolay Ivchenko 《Journal of Atmospheric and Solar》2009,71(16):1677-1680
An often observed and still unexplained feature of the high-m Alfvén waves in the terrestrial magnetosphere is their equatorward phase motion, in contrast with low-m waves. We suggest an explanation of this fact in terms of a model of wave excitation by an azimuthally drifting particle inhomogeneity injected during substorm activity. The azimuthal direction of the phase velocity coincides with that of the cloud. If the drift velocity increases with the radial coordinate, the particle cloud is stretched into spiral in the equatorial plane which leads to a radial component of the phase velocity directed toward Earth, that is, an equatorward phase propagation. 相似文献
33.
Ilia Louban Nicole Bobrowski Dmitri Rouwet Salvatore Inguaggiato Ulrich Platt 《Bulletin of Volcanology》2009,71(7):753-765
The simultaneous quantitative determination of two-dimensional bromine monoxide (BrO) and sulphur dioxide (SO2) distributions in volcanic gas plumes is described. Measurements at the fumarolic field on the island Vulcano (autumn 2004)
and in the plume of Mt. Etna volcano (spring 2005) were carried out with an Imaging DOAS instrument. The SO2 fluxes of several fumaroles were estimated from two-dimensional distributions of SO2. Additionally, the first two-dimensional distributions of BrO within a volcanic plume were successfully retrieved. Slant
column densities of up to 2.6 × 1014 molecules per square centimetre were detected in the plume of Mt. Etna. The investigation of the BrO/SO2 ratio, calculated from the two-dimensional distributions of SO2 and BrO, shows an increase from the centre to the edge of the volcanic plume. These results have significance for the involvement
of ozone during BrO formation processes in volcanic emissions. 相似文献
34.
Dmitri?A.?IonovEmail author Vladimir?S.?Prikhodko Jean-Louis?Bodinier Alexander?V.?Sobolev Dominique?Weis 《Contributions to Mineralogy and Petrology》2005,149(6):647-665
We provide petrographic, major and trace element data for over 30 spinel peridotite xenoliths from the Tokinsky Stanovik (Tok) volcanic field on the Aldan shield to characterize the lithospheric mantle beneath the south-eastern margin of the Siberian craton, which formed in the Mesoproterozoic. High equilibration temperatures (870–1,010°C) of the xenoliths and the absence of garnet-bearing peridotites indicate a much thinner lithosphere than in the central craton. Most common among the xenoliths are clinopyroxene-poor lherzolites and harzburgites with Al2O3 and CaO contents nearly as low as in refractory xenoliths from kimberlite pipes (Mir, Udachnaya) in the central and northern Siberian craton. By contrast, the Tok peridotites have higher FeO, lower Mg-numbers and lower modal orthopyroxene and are apparently formed by shallow partial melting (3 GPa). Nearly all Tok xenoliths yield petrographic and chemical evidence for metasomatism: accessory phlogopite, amphibole, phosphates, feldspar and Ti-rich oxides, very high Na2O (2–3.1%) in clinopyroxene, LREE enrichments in whole-rocks.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
35.
36.
The shelfbreak wintertime thermal front in the Northeastern Gulf of Mexico often exhibits meandering, eddy formation and warm-water
intrusion. A high level of frontal variability plays an essential role in exchange processes across the shelf. This study
examines the impacts of local frontal instability and bottom topography on turbulent heat exchange across the front using
the results of two numerical models. Analysis of a series of numerical experiments reveals that the flow is baroclinically
unstable. Predicted frontal instability contributes significantly to cross-frontal exchange and accounts for about 35% of
the total eddy heat flux. Onshore eddy heat flux has the highest intensity at the frontal position. In addition, eddy activity
and heat flux are sensitive to variation of bottom topography. For topographic features and frontal characteristics that are
typical of the area, bottom steepness enhances the flux and is nearly proportional to the cross-frontal heat exchange. The
study attempts to explain physical mechanisms that drive frontal circulation in the area and to quantify heat transport across
the shelf. Estimated heat fluxes can provide important information for climate and ecosystem modeling of the Mississippi Bight. 相似文献
37.
Gleb Panteleev Motoyoshi Ikeda Alex Grotov Dmitri Nechaev Max Yaremchuk 《Journal of Oceanography》2004,60(3):613-623
Standard hydrological section data, collected in the eastern Barents Sea in September 1997, have been analyzed using a variational
data assimilation technique. This method allows us to obtain temperature, salinity and velocity fields that are consistent
with observations and dynamically balanced within the framework of a steady-state model describing large-scale nearly geostrophic
circulation. Error bars of the optimized fields are computed by explicit inversion of the Hessian matrix. The optimized velocity
field is in agreement with independent velocity observations derived from surface drifter trajectories in the southwestern
part of the Barents Sea. Optimized fields provide the following estimates of integral characteristics of the circulation in
the region: i) the North Cape current transport is 2.12 ± 0.25 Sv; ii) the Karskie Vorota Strait throughflow is 0.7 ± 0.06
Sv; iii) heat flux with Atlantic water is 4.7 ± 0.16⋅1011 W; iv) salt import from the Atlantic Ocean is 7.41 ± 0.46⋅103 kg/s. The imbalance of the heat budget in the eastern part of the Barents Sea indicates the presence of statistically insignificant
surface heat fluxes which are less than 1 W/m2.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
38.
Ya. A. Virolainen Yu. M. Timofeyev A. V. Polyakov D. V. Ionov O. Kirner A. V. Poberovskii H. Kh. Imhasin 《Izvestiya Atmospheric and Oceanic Physics》2016,52(1):57-65
Chemistry climate models of the gas composition of the atmosphere make it possible to simulate both space and time variations in atmospheric trace-gas components (TGCs) and predict their changes. Both verification and improvement of such models on the basis of a comparison with experimental data are of great importance. Data obtained from the 2009–2012 ground-based spectrometric measurements of the total contents (TCs) of a number of TGCs (ozone, HNO3, HCl, and NO2) in the atmosphere over the St. Petersburg region (Petergof station, St. Petersburg State University) have been compared to analogous EMAC model data. Both daily and monthly means of their TCs for this period have been analyzed in detail. The seasonal dependences of the TCs of the gases under study are shown to be adequately reproduced by the EMAC model. At the same time, a number of disagreements (including systematic ones) have been revealed between model and measurement data. Thus, for example, the EMAC model underestimates the TCs of NO2, HCl, and HNO3, when compared to measurement data, on average, by 14, 22, and 35%, respectively. However, the TC of ozone is overestimated by the EMAC model (on average, by 12%) when compared to measurement data. In order to reveal the reasons for such disagreements between simulated and measured data on the TCs of TGCs, it is necessary to continue studies on comparisons of the contents of TGCs in different atmospheric layers. 相似文献
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