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1.
引力常数变化对地球自转长期变化的影响 总被引：1，自引：0，他引：1
李林森 《中国科学院上海天文台年刊》2002,(1)
探讨和估计了各种引力常数变化理论对地球角速度和日长变化的影响。各种引力常数变化理论包括了引力常数G随时间、空间以及速度变化等几个方面的影响。另外也估计了对地球自转角速度和日长变化产生的效应。其中有些研究对探讨地球自转变化也有启发意义。 相似文献
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V. V. Sidorov S. A. Kalabanov D. V. Lyubimov A. F. Nasyrov A. D. Sidorova I. V. Filin 《Solar System Research》2008,42(3):194-208
The results of an analysis of the orbital structure of the meteor complex accessible for radar observations at northern midlatitudes are reported. Experimentally, the study is based on the long-term monitoring of the influx of meteor matter into the Earth’s atmosphere performed with the meteor radar of Kazan State University starting from 1986. The study uses a discrete quasi-tomographic method to measure the radiants and velocities of meteor showers based on goniometric data of the meteor radar and diffraction measurements of meteor velocities. The discretization of the detection environment—in particular, in terms of velocity—is shown to result in no substantial loss of measurement accuracy. The error of the measured velocity of the shower does not exceed 1.5 km/s for a standard deviation of a single velocity measurement equal to 3 km/s. Microshower representation is used with microshowers either representing the correlated part of the sporadic complex or being partial streams of major and minor showers, or fragments of the dust environment of minor bodies passing by Earth or falling onto it. The data of measurements made over the entire annual cycle are used to construct combined maps of the distribution of the observed 2263 microshowers (a total of 22 604 orbits) by their inclination, aphelion distance, and longitudes of the ascending nodes of their orbits. The observing conditions are shown to have a significant effect on the parameters of the distribution of aphelion distances for different months, and the corresponding distributions for prograde and retrograde orbits are shown to differ fundamentally. A specific feature of such distribution maps is that they allow uniform representation of both meteor showers and irregularities of the sporadic complex. 相似文献
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Some results of the photographic observations of double stars with 65 cm refractor of Pulkovo observatory are presented. We use the apparent motion parameters (AMP) method which allows to determine the orbits and to carry out the dynamical investigation of wide binaries on the basis of a short arc of their orbital motion. We have determined more than 40 orbits for wide pairs and also the sum of masses and in some cases—the mass-ratio of components. The references to our works and the basic results of observations are contained in Kisselev et al. [2004. Catalogue of relative positions of visual double stars made on the observations with 26″ refractor of Pulkovo observatory. Strassbourg, I/297]. We apply two ways of revealing the hidden mass of our stars, namely: revealing of possible perturbations from comparison of observational and calculated positions using differences O-C (for instance, perturbations in the orbital motion of ADS 15571) and also by means of comparison of the sum of the masses obtained by us and the sum of the masses obtained by means of the mass-luminosity relation. An excess of masses of about 1-3 solar masses is detected for binaries: ADS 497, ADS 8450 and ADS 10329 by means of last method.The estimations of the masses for some binaries are discussed. Also we justify the necessity of precise parallaxes and relative radial velocities of stars, which could be measured by space telescopes such as the GAIA as the additional parameters for determination of orbits of binaries. 相似文献
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M. V. Samokhin 《Astrophysics and Space Science》1979,62(1):159-183
In order to understand the reason of the existence of the electric field in the magnetosphere, and for the theoretical evaluation of its value, it is necessary to find the solution of the problem of determination of the magnetosphere boundary form in the frameworks of the continuum medium model which takes into account part of the magnetospheric plasma movement in supporting the magnetospheric boundary equilibrium. A number of problems for finding the distribution of the pressure, the density, the magnetic field and the electric field on the particular tangential discontinuity is considered in the case when the form of discontinuity is set (the direct problem) and a number of problems for finding the form of the discontinuity and the distribution of the above-mentioned physical quantities on the discontinuity is considered when the law of the change of the external pressure along the boundary is set (for example, with the help of the approximate Newton equation). The problem which is considered here, which deals with the calculation of the boundary form and with the calculation of the distribution of the corresponding physical quantities on the discontinuity of the 1st kind for the compressible fluid with the magnetic field with field lines which are perpendicular to the plane of the flow in question, concerns the last sort of problems. The comparison of the results of the calculation with the data in the equatorial cross-section of the magnetosphere demonstrates that the calculated form of the boundary, the value of the velocity of the return flow and the value of the electric field on the magnetopause, agree satisfactorily with the observational data. 相似文献
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M. A. Vashkov’yak 《Solar System Research》2016,50(6):390-401
The problem of the secular perturbations of the orbit of a test satellite with a negligible mass caused by the joint influence of the oblateness of the central planet and the attraction by its most massive (or main) satellites and the Sun is considered. In contrast to the previous studies of this problem, an analytical expression for the full averaged perturbing function has been derived for an arbitrary orbital inclination of the test satellite. A numerical method has been used to solve the evolution system at arbitrary values of the constant parameters and initial elements. The behavior of some set of orbits in the region of an approximately equal influence of the perturbing factors under consideration has been studied for the satellite system of Uranus on time scales of the order of tens of thousands of years. The key role of the Lidov–Kozai effect for a qualitative explanation of the absence of small bodies in nearly circular equatorial orbits with semimajor axes exceeding ~1.8 million km has been revealed. 相似文献
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Some peculiarities of the use of a laser for the determination of the instrumental profile of the high-resolution spectrograph have been described. The results of the investigation of the instrumental profile of the Kiev-Golosejevo double-pass solar spectrograph are presented in graphs.The influence of the width of the slits of the double-pass spectrograph upon the main features of its instrumental profile is discussed briefly. 相似文献
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B. P. Kondratyev 《Solar System Research》2013,47(1):1-10
A two-component theoretical model of the physical libration of the Moon in longitude is constructed with account taken of the viscosity of the core. In the new version, a hydrodynamic problem of motion of a fluid filling a solid rotating shell is solved. It is found that surfaces of equal angular velocity are spherical, and a velocity field of the fluid core of the Moon is described by elementary functions. A distribution of the internal pressure in the core is found. An angular momentum exchange between the fluid core and solid mantle is described by a third-order differential equation with a right-hand side. The roots of a characteristic equation are studied and the stability of rotation is proved. A libration angle as a function of time is found using the derived solution of the differential equation. Limiting cases of infinitely large and infinitely small viscosity are considered and an effect of lag of a libration phase from a phase of action of an external moment of forces is ascertained. This makes it possible to estimate the viscosity and sizes of the lunar fluid core from data of observations. 相似文献
10.
Observations of near-Earth asteroids at large phase angles made it possible to obtain a more complete (for ground-based observations) phase dependence of the polarization of the E-type asteroids’ radiation including the maximum of the positive branch of the linear polarization degree. It is shown that the position of the polarization maximum of high-albedo asteroids is noticeably shifted to the decrease of phase angles compared with S-type asteroids. Model calculations of polarimetric properties of random Gaussian particles that simulate dust particles on the regolith surface are carried out. Model calculations show a qualitatively similar behavior pattern of parameters of the positive polarization branch. The influence of the refractive index of individual scattering particles on the size and position of the maximum of the positive branch of the linear polarization degree is investigated within the considered model. 相似文献
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In the traditional axisymmetric models of the 11-year solar cycle, oscillations of the magnetic fields appear in the background of nonoscillating (over time scale considered) turbulent velocity fields and differential rotation. In this paper, an alternative approach is developed: The excitation of magnetic oscillations with the 22-year period is the consequence of hydrodynamic oscillations with the 11-year period. In the excitation of hydrodynamic oscillations, two processes taking place in high latitudes near the interface between the convective and radiative zones play a key role. One is forcing of the westerly zonal flow, the conditions for which are due to deformation of the interfacial surface. The other process is the excitation of a shear instability of zonal flow as a consequence of a strong radial gradient of angular velocity. The development of a shear instability at some stage brings about the disruption of the forcing of differential rotation. In the first (hydrodynamic) part of the paper, the dynamics of axisymmetric flows near the bottom of the convection zone is numerically simulated. Forcing of differential rotation having velocity shear in latitude and the existence of solutions in the form of torsional waves with the 11-year oscillation period are shown. In the second part the dynamics of the magnetic field is studied. The most pronounced peculiarities of the solutions are the existence of forced oscillations with the 22-year period and the drift of the toroidal magnetic field component from the mid latitudes to the equator. In high and low latitudes after cycle maximum, the toroidal component is of opposite sign in accordance with observations. In the third part, the transport of momentum from the bottom of the convection zone to the outer surface by virtue of diffusivity is considered. The existence of some sources of differential rotation in the convection zone is not implied. A qualitative correspondence of the differential rotation profile in the bulk of the convection zone and on its outer surface to experimental data is shown. The time correspondence between torsional and magnetic oscillations is also in accordance with observations. 相似文献
12.
V. V. Zheleznyakov 《Astrophysics and Space Science》1971,13(1):87-99
A model of pulsars is discussed in which formation of a polar diagram of the radiation is influenced by the motion of the source around a neutron star with a velocity close to that of light. For a power-law frequency-spectrum of the radiation and isotropy of the diagram in a system of coordinates rotating with the source, the width of the observed pulse is shown to be independent of frequency.The proposed explanation of the second period characteristics of type CP 1919 pulsars is based on the effect of relativistic motion of the radiation source. The positions are established (relative to the axis of rotation of the star) of the local sources of radiation in the optical and in the radio ranges for the pulsar NP 0532. It is shown how the polarization characteristics of the optical radiation of this pulsar may be connected with the effects of relativistic orbiting of the source of radiation about the star. 相似文献
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A technique for the analysis of photoelectrically scanned double star images is described. The method consists of comparing the Fourier transform of the double star profile with that of a single star profile imaged through the same telescope. If the measured profile of the double star image can be considered to be a linear superposition of two profiles, each identical in shape to the measured profile of a nearby single star, a comparison of the Fourier transforms of these profiles enables the parameters of the double star system to be determined. Certain features of the ratio of the moduli of the transforms yield both the separation and the magnitude difference between the components. A comparison of the phases of the transforms enables one to establish which of the two components is the brighter. 相似文献
14.
Two-integral distribution functions for axisymmetric systems 总被引：1，自引：0，他引：1
Zhenglu Jiang Leonid Ossipkov 《Monthly notices of the Royal Astronomical Society》2007,379(3):1133-1142
Some formulae are presented for finding two-integral distribution functions (DFs) which depend only on the two classical integrals of the energy and the magnitude of the angular momentum with respect to the axis of symmetry for stellar systems with known axisymmetric densities. They come from a combination of the ideas of Eddington and Fricke and they are also an extension of those shown by Jiang and Ossipkov for finding anisotropic DFs for spherical galaxies. The density of the system is required to be expressed as a sum of products of functions of the potential and of the radial coordinate. The solution corresponding to this type of density is in turn a sum of products of functions of the energy and of the magnitude of the angular momentum about the axis of symmetry. The product of the density and its radial velocity dispersion can be also expressed as a sum of products of functions of the potential and of the radial coordinate. It can be further known that the density multiplied by its rotational velocity dispersion is equal to a sum of products of functions of the potential and of the radial coordinate minus the product of the density and the square of its mean rotational velocity. These formulae can be applied to the Binney and the Lynden-Bell models. An infinity of the odd DFs for the Binney model can be also found under the assumption of the laws of the rotational velocity. 相似文献
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The investigation of plasma tails of comets is an important part of comet research. Different classifications of plasma tails of comets are proposed. Plasma acceleration in the tails is investigated in sufficient detail. Several cometary forms are explained. Plasma tails of Mars and Venus were observed during the first studies of these planets. They are associated with the capture of ionized atoms and exosphere molecules by the solar wind magnetized plasma flow. Distinct plasma tails of Mars and Venus are caused by the mass loading of the solar wind with heavy ions. It was shown that the transverse dimension of the tails of Mars, Venus, and comets can be quite accurately determined by production rate of the obstacle to the solar wind flow. While plasma tails of Mars and Venus are investigated by in situ measurements from spacecraft, observations of comet tails from the Earth make it possible to see the entire object under study and to monitor changes in its structure. A certain similarity of cometary and planetary tails can be explained by the nonmagnetic nature of both types of bodies. Thus, it is reasonable to suppose that investigations of plasma tails of comets can supplement the information obtained by in situ methods of the study of the planets. In this paper, plasma tails of comets, presumably analogous to the plasma tails of Mars and Venus, have been identified on modern photographs of comets (more than 1500 photographs viewed). Only quasi-steady laminar tails are considered. They are divided into two types: double structures and outflows. The paper attempts to define the 3D structure of double structures and to determine certain characteristics of outflows. 相似文献
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We study the problem of the reconstruction of a non-stationary space symmetrical regular planar potential of the gravitating system on a family of evolving types of orbits being used in the dynamics of stationary stellar systems. An application of such an inverse problem to the dynamical evolution of stellar systems with variable masses is given. The general form of the evolving orbit which we use when writing out the differential equations for non-stationary potential may also be interpreted as an osculating orbit of the perturbed Keplerian motion. In this case we are making an additional transformation of the basic equation of the problem and demonstrating an appropriate example of the construction of a non-stationary potential of a gravitating system. In connection with the stellar dynamical character of our inverse problem, we also give a generalized form of its basic equation in a rotating coordinate system. 相似文献
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This paper describes the results of studies of dynamical chaos in the problem of the orbital dynamics of asteroids near the 3 : 1 mean-motion resonance with Jupiter. Maximum Lyapunov characteristic exponents (MLCEs) are used as an indicator and a measure of the chaoticity of motion. MLCE values are determined for trajectories calculated by the numerical integration of equations of motion in the planar elliptical restricted three-body problem. The dependence of the MLCE on the problem parameters and on the initial data is analyzed. The inference is made that the domain of chaos in the phase space of the problem considered consists of two components of different nature. The values of the MLCEs observed for one of the components (namely, for the component corresponding to low-eccentricity asteroidal orbits) are compared to the theoretical estimates obtained within the framework of model of the resonance as a perturbed nonlinear pendulum. 相似文献
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K. L. Coulson 《Planetary and Space Science》1959,1(4):265-276
S. Chandrasekhar's solution of the equation of radiative transfer m a medium scattering according to Rayleigh's law has been used for an extensive series of computations of the scattered and diffusely reflected radiation directed outward from the top of a plane stratified model of the atmosphere. The results are discussed in two parts, the first of which deals with the intensity, degree of polarization, plane of polarization and the neutral points of the scattered and diffusely reflected radiation. Part II (see following article) will be a discussion of the upward flux, integrated over the hemisphere, as a function of wavelength of the incident radiation, and of the albedo of the atmospheric model for an energy distribution of the incident light similar to that of the extra-terrestrial solar spectrum. The results are compared with similar quantities for the diffusely scattered radiation from the sunlit sky. 相似文献
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The problem of motions of charged particles or charged grains of matter in the field of two magnetic dipoles in rotation about a common center are studied by means of computing families of periodic solutions and their stability. Ten such families are found and their stability study shows that only two out of the ten have short arcs of stable members, all with low inclination to the plane of the two dipoles, while the rest of the families consist exclusively of unstable solutions. Hence the impact of adding one dipole to the configuration of the Störmer problem, leads to the conclusion that in the modified system the three-dimensional motions are basically unstable unlike those of the one-dipole case. The model magnetic field used in this study is a first approximation of the Z3model of the magnetic field of Saturn as computed from the Pioneer 11 and Voyager 1 and 2 measurements. 相似文献
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The masses of a pair of stars in the visual binary system have been estimated. The angle between the orbital plane of the stars and the plane of the sky has been taken into account. Inclination of the major axes of the orbits of the stars with the line of interaction between the orbital plane and the plane of the sky has also been considered. These two inclinations are also computed in terms of the observed quantities. Major and minor axes of actual orbits of the stars are determined. 相似文献