The Dependence of Water Exchanges between the Kuroshio Water and Its Surroundings on the Characteristics of the Kuroshio‘s Meanders     

姜华  吴德星  万修全 《中国海洋湖沼学报》2003,21(4):335-344

Observation of fluid parcel pathways in the Kuroshio Stream revealed a striking crossstream pattern associated with the Kuroshio‘‘ s meanders. In order to understand the observed pattern, a two-dimensional kinematic model of a meandering jet was developed which could be used to examine the relationship between streamfunction patterns and fluid parcel trajectories. The experiments designed to investigate the dependence of the water exchanges between the Kuroshio water and its surroundings on the characteristics of the Kuroshio‘‘s meanders involved the downstream speed,phase speed and the amplitude of other propagating waves. The results suggested that fluid parcels could cross the meandering jet to and fro; and that the water exchanges between the Kuroshio and its surroundings increased with a) increasing meander amplitude, b) decreasing downstream speed, and c) increasing wave phase speed. The results also showed that when the meandering jet was disturbed by other propagating waves, more effective water exchanges could be induced.  相似文献   

A note on the algorithm of symplectic integrators     

Xin Wu  Tian-Yi Huang  Hong Zhang  Xiao-Sheng Wan 《Astrophysics and Space Science》2003,283(1):53-65

For a Hamiltonian that can be separated into N+1(N\geq 2) integrable parts, four algorithms can be built for a symplectic integrator. This research compares these algorithms for the first and second order integrators. We found that they have similar local truncation errors represented by error Hamiltonian but rather different numerical stability. When the computation of the main part of the Hamiltonian, H ₀, is not expensive, we recommend to use S ^* type algorithm, which cuts the calculation of the H ₀ system into several small time steps as Malhotra(1991) did. As to the order of the N+1 parts in one step calculation, we found that from the large to small would get a slower error accumulation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Spine–sheath polarization structures in four active galactic nuclei jets     

A. B. Pushkarev  D. C. Gabuzda  Yu. N. Vetukhnovskaya  V. E. Yakimov 《Monthly notices of the Royal Astronomical Society》2005,356(3):859-871

We present the results of multifrequency (15 + 8 + 5 GHz) polarization Very Long Baseline Array (VLBA) observations of the three BL Lacertae objects 0745+241, 1418+546 and 1652+398 together with 5-GHz VLBI Space Observatory Programme (VSOP) observations of 1418+546 and 1.6- and 5-GHz VSOP observations of the blazar 1055+018. The jets of all these sources have polarization structure transverse to the jet axis, with the polarization E vectors aligned with the jet along the jet spine and 'sheaths' of orthogonal E vectors at one or both edges of the jet. The presence of polarization aligned with the jet near the 'spine' may indicate that the jets are associated with helical B fields that propogate outward with the jet flow; the presence of orthogonal polarization near the edges of the jet may likewise be a consequence of a helical jet B field, or may be owing to an interaction with the ambient medium on parsec scales. We have tentatively detected interknot polarization in 1055+018 with E aligned with the local jet direction, consistent with the possibility that the jet of this source is associated with a helical B field.  相似文献   

Faint galaxies: merging model of E/SO galaxies     

Wen Xu  Yunqiang Yu 《Astrophysics and Space Science》1995,226(2):309-328

We study a model of mergers affecting only the progenitors of present E/SO. We adopt the standard scenarios of star formation as prescribed by Guiderdoni & Rocca-Volmerange. The merging process is parametrized under the assumptions of(1) self-similarity of the Schechter MF and(2) mass conservation. Nine models are discussed. The predictions are compared with counts ofB _J ,U ⁺,F ⁺,N ⁺ bands. E/SO mergers account for the excess of the faintest blue galaxies without causing excess in redder bands. However, as we no longer have enough mergers at brighter magnitudes, a plain E/SO merging model fits less tightly for the redshift and the colour distributions. Detection effect, a steeper slope of LF may be ways to improve. Our models predict acceptable merger frequencies atz = 0.5 although some models predict more interacting galaxies than observation atz = 0.  相似文献   

A kinetic model of gas flow in a porous cometary mantle     

Yu. V. Skorov  H. Rickman   《Planetary and Space Science》1995,43(12)

A numerical study of gas flow through a porous cometary mantle is presented. A kinetic model based on the well-known Test Particle Monte Carlo Method for the solution of rarefied gas dynamics problems is proposed. The physical model consists of two spatial plane regions: the condensed ice phase and a porous dust mantle. The structure of the porous dust layer is described as a bundle of cylindrical inclined channels not crossing each other. A vertical temperature gradient may exist across the dust mantle. The aim is to investigate how the characteristics of molecular flow depend on the capillary length, inclination angle, and temperature gradient. Examples illustrating a significant deviation of some results from equilibrium values are shown. In particular, the gas velocity distribution at both ends of the pore is strongly non-Maxwellian if there is an important temperature contrast across the pore. The emergent gas flow rate is found to vary with the pore length/radius ratio in excellent agreement with Clausing's empirical formula. The degree of collimation of the flow is quantitatively studied as a function of the length/radius ratio, and consequences for the jet force of outgassing through a dust mantle or, indeed, a rough surface are estimated.  相似文献   

Computer simulation of the particle acceleration in pulsar magnetospheres     

Yu. A. Rylov 《Astrophysics and Space Science》1987,132(2):353-386

In the spherically-symmetric case, a computer simulation of the electron acceleration inside the outflow channel of the pulsar magnetosphere is produced. The stationary motion of electrons is shown to be unstable in the case of > _c, where is a parameter describing inhomogeneity of the background charge, and _c is its critical value. The arising non-stationary motion of electrons leads to a formation of electron bunches, which move chaotically. The mean electron energy appears to be much greater at the non-stationary motion, than at the stationary one. The time-averaged parameters of the non-stationary electron flow and their dependence upon have been investigated. Distributions of the mean values of parameters (charge density, electron velocity, electric field energy density, pressure, and internal energy of the gas composed of the electron bunches) over the magnetosphere altitude have been investigated. The mean spectra of the charge density have been obtained. The results of numerical investigation of the spherically-symmetric model are used for estimation of the electron energy and of the electron flux in the case of the more realistic model. The radioemission loss is estimated, and is shown to be large enough for explaining the radiopulsar phenomenon as a thermal radioemission of the pulsar magnetosphere. In particular, such common properties of the pulsar radioemission as the high bright temperature, the sharp radioemission directivity, and the characteristic turn-over of the radioemission spectrum at the frequency of the order 10⁸ Hz are found a natural explanation in frames of this model.  相似文献   

The production of light elements in unconventional cosmologies with VMOs     

Yu. A. Shchekinov  B. V. Vainer 《Astrophysics and Space Science》1986,123(1):103-115

The abundances of light elements (deuterium, helium and lithium) are calculated in unconventional cosmologies in which these elements are produced by interaction of fast -particles ejected by massive pregalactic stars with a purely hydrogenous cosmological substrate. The number density and energetics of such stars needed for suitable production of light elements are estimated. It is shown that the models always lead to overproduction of lithium. The intensity of ultraviolet, X-ray, and -ray emission caused by explosions of pregalactic massive stars is calculated. The distortions of cosmic background radiation by Compton losses of electrons heated by explosive stars are also calculated.  相似文献   

Hydrodynamical models of type II supernovae     

I. Yu. Litvinova  D. K. Nadyozhin 《Astrophysics and Space Science》1983,89(1):89-113

A series of hydrodynamical models of type-II supernova outbursts (SNII) has been calculated. Approximate relations connecting the total outburst energy ε, the mass of envelope ejectedM, the presupernova radiusR, and the amount of ionizing quanta radiated by the supernovaeN _H with such values as the duration of the light curve plateau Δt, and absolute magnitude in the wavelength bandV and photospheric velocityU _PH observed near the middle of the plateau have been established. Advantage has been taken of the relations to obtain a preliminary evaluation for the characteristics of the average SN II: ε=7×10⁵⁰ erg,M=6M _⊙,R=500R _⊙,N _H=2×10⁵⁸. The SNIIs with plateau-like light curves seem to be accounted for by thermonuclear explosions of degenerate cores of red giant stars and result in a total disruption of the star without any stellar remnant. To the contrary, SNIIs with linear light curves have substantially different properties (in particular, they throw considerably less massive envelopes off). These SNII must signify the birth of collapsed objects—neutron stars (pulsars) or black holes.  相似文献   

Georgii Pavlovich Leonov (on the centenary of his birth)     

D. Yu. Pushcharovskii  E. E. Milanovskii  A. M. Nikishin  N. V. Koronovskii  O. V. Yapaskurt  I. S. Barskov  D. P. Naidin  V. T. Frolov  D. I. Panov 《Moscow University Geology Bulletin》2008,63(5):350-351

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Evolution of melt composition during intrusion of basalts into a silicic magma chamber   总被引：3，自引：0，他引：3  

P. Yu. Plechov  I. S. Fomin  O. E. Mel’nik  N. V. Gorokhova 《Moscow University Geology Bulletin》2008,63(4):247-257

The article describes heat exchange between basaltic and rhyolite melts accompanied by fractional crystallization of phases in a basaltic melt. A numerical model has been developed for the homogenization mechanism of magma composition during intrusion of basaltic magma batches into felsic magma chambers. The results of numerical modeling demonstrate that the time needed for cooling the basalts and their fractionation to rhyolite melts is much shorter than the time required for chemical interaction based on diffusive mechanisms.  相似文献