On the formation of pulsar radiation diagrmas

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.     

Two-integral distribution functions for axisymmetric systems

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.     

The 1997 Campaign of Observations of Mutual Occultations and Eclipses in the System of Jupiter's Galilean Satellites: Final Results

This paper presents the final results of the campaign of photometric observations of the Galilean satellites of Jupiter at the time of their mutual occultations and eclipses at the epoch of 1997 at observatories of Kazakhstan, Russia, and Ukraine. These results essentially contribute to the worldwide database of this type. They will help to refine the models of motion of the Galilean satellites of Jupiter. A comparison is made of the obtained data with the results of the worldwide campaign of observations of mutual occultations and eclipses in 1997. From the results of these observations, the differences of planetocentric coordinates of two satellites are calculated for a sequence of instants of time. Processing is based on the theory and the model of mutual occultations and eclipses of natural planetary satellites, which were developed by one of the authors in previous papers (Emel'yanov, 1999, 2000). In this paper, some new elements of the technique were used. We estimated the accuracy of observations. The paper contains information on the observing conditions and describes briefly the instruments employed.     

Reflectance model for densely packed media: Estimates of the surface properties of the high-albedo satellites of Saturn

Interpretation of photometric and polarimetric observations of atmosphereless celestial bodies faces the problems connected with both the insufficient accuracy and level of details in groundbased observations and the current state of the theory of the multiple scattering of light. In application to sparse media, where the electromagnetic waves, propagating between the scatterers, can be considered as spherical (the socalled far-field approximation), this theory is rather well developed for both the diffuse and coherent components of the scattered radiation. In this paper, we show that this theory can be also successfully applied to the measurements of polarization of light scattered by densely packed, though nonabsorbing or weakly absorbing, media. For this purpose, we calculated the models for a semi-infinite layer of the medium composed of randomly oriented clusters of spherical particles and compared them with the data of laboratory and astronomical measurements. The potential of the present approach is illustrated by an example of the interpretation of the polarization measurements of the ice satellites of Saturn—Rhea and Enceladus—which allowed some properties of the surface of these celestial bodies to be estimated. In particular, the ratio of the surface area that makes no contribution to the negative polarization of light reflected at small phase angles to the area producing the negative polarization branch was found. Under the assumption of the same albedo of these areas, this ratio turned out to be 3.31–3.66 and 1.7–3.8 for Rhea and Enceladus, respectively. For Enceladus, it is difficult to obtain a sufficiently narrow range of the estimated parameters, since the number of measurement points in the phase dependence of polarization of this satellite is small. For the surface of Rhea, the estimated packing density of particles, participating in the opposition effects, is approximately 15%, while their smallest size is of the order of the wavelength of visible light.     

Precision of the ephemerides of outer planetary satellites

Ephemerides of planetary satellites are needed to address many problems. These ephemerides are used for subsequent observations. A comparison of the available ephemerides with new observations allows the accuracy of the former to be assessed. However, the precision of the ephemerides must be known a priori when solving the tasks. In this paper we formulate and solve the problem of estimating the precision of the ephemerides of outer planetary satellites derived from observations when applied up to the future moments.The methods of assessing the precision of ephemerides involve producing a set of samples of the same ephemeris inferred from observations with different samples of Monte Carlo generated random errors (RO) superimposed onto it. The statistical parameters of simulated observational errors are based on the results of the reduction of real satellite observations. We compute the deviations of the samples of the ephemeris from the standard ephemeris inferred from real observations and adopt the root-mean-square deviation of the apparent coordinates as the precision of the ephemeris. We also use alternative methods: one based on the matrix of covariances of parameter errors (RP), and another one based on bootstrap samples of observations (BS).We use three methods (RO, RP, and BS) to estimate the precision of the ephemerides of all the 107 outer planetary satellites over the 2010-2020 time interval. The precision of the ephemerides of different satellites varies from 0.05 to 4.0 arcsec. For a number of satellites new observations are of vital importance for maintaining the precision of the ephemerides at a level that would allow identification of satellites during the reduction of observations. For some satellites the precision of their ephemerides is of the order of the sizes of their orbits and such satellites can be considered to have been lost. We show that the method of bootstrap samples (BS) can give doubtful results in the cases where there are few observations, which covered a time interval that is shorter than the orbital period of the satellite.Our results suggest obtaining more precise ephemeris making new observations at the times of maximum estimated errors of the ephemeris.All the inferred estimates of the precision of ephemerides are available from the MULTI-SAT ephemeris server: www.imcce.fr/sat (IMCCE), www.sai.msu.ru/neb/nss/index.htm (SAI).     

New Numerical/Analytical Methods for Solving Equations of Orbital Motion

New methods are proposed for solving equations of motion of celestial bodies. The methods are based on the use of superosculating orbits with second- and third-order tangency to the trajectory of the real motion of a body. The construction of these orbits is related to the concept of a fictitious attracting center, whose mass varies in accordance with the first Meshchersky law. In the original reference methods, the perturbed trajectory is represented by a sequence of small arcs of superosculating orbits. The order of accuracy of the reference methods coincides with the order of tangency of the superosculating orbit used in calculations. Using Runge's rule and Richardson's extrapolation scheme leads to the methods of higher order. The efficiency of the new methods in comparison with the numerical integration of equations of motion based on the well-known fourth- and seventh-order Runge–Kutta–Fehlberg methods is illustrated by examples of the calculation of perturbed orbits of some asteroids.     

Solar oscillations: Past,present, and future

Observation of global oscillations of the Sun constitutes a primitive seismology of the solar interior. The frequencies, if correctly identified with definite normal modes of vibration, provide a measure of the average velocity of sound in the interior and thereby of its composition and temperature. Fine structure in the frequencies of nonradial modes may provide information on their character (multiplicity) and on the rotation of the solar interior. Study of the amplitudes and phase fluctuations of the vibrations may clarify the excitation and damping of the vibrations.After a brief historical review emphasizing global velocity spectroscopy an account is given of the present status of the observations of global oscillations in the range of periods of 3 to 160 min.Finally the future capabilities of the observational techniques and their resultant potential is discussed.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

Tectonics and Evolution of Novae and Coronae on Venus: Tectonophysical Modeling Based on Gravitational Models

This paper describes the results of tectonophysical modeling of the formation and evolution of novae and coronae—radial/concentric volcanotectonic structures typical of the surface of Venus. The formation of these structures is usually associated with the effect of the rising and subsequently relaxing mantle diapirs on the surface layers of the lithosphere. Two series of experiments with gravitational models reproduce the topographic changes and the evolution of structural patterns in the course of the formation of novae and coronae on Venus. For model materials, we chose (1) rubber (a Bingham liquid) to reproduce the behavior of the elastoviscous diapir material in one series of experiments and the lower part of the lithosphere in the other series and (2) flour to model tectonic structures in the upper, brittle part of the lithosphere. Regularities in the formation of the topographic and structural characteristics of novae and coronae have been demonstrated on models of different geometry. The process of formation of the dense radial fracturing in novae due to the mechanical elevation caused by the formation of a rising dome, which was suggested by many authors, is not corroborated by our models. In the course of modeling, we studied the influence of the relative dimensions of the diapir and the thickness of the overlying structures, or the relative depth of the neutral buoyancy surface of the diapir, on the topographic, morphological, and structural features of novae and coronae and on the possible paths of their evolution. Regularities are also revealed in the formation of tectonic structures in relation to the environment in which the diapir evolution occurs—in the brittle upper part of the lithosphere or in its lower, viscoplastic part.     

Numerical theories of motion of Triton and Nereid

The ephemerides of satellites of major planets are needed in planning spacecraft missions both for studying the satellites themselves and for navigational support during the flights of spacecraft in the vicinity of planets. In addition, accurate numerical theories of motion of the natural satellites of major planets make it possible to increase the accuracy of the ephemerides of their central planets based on positional (photographic and CCD) observations of the satellites. Numerical theories of Neptune’s satellites, Triton and Nereid, constructed within the framework of the ERA software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences are presented.     

Solar oscillations and the equation of state

Summary Accurate measurements of observed frequencies of solar oscillations are providing a wealth of data on the properties of the solar interior. The frequencies depend on solar structure, and on the properties of the plasma in the Sun. Here we consider in particular the dependence on the thermodynamic state. From an analysis of the equations of stellar structure, and the relevant aspects of the properties of the oscillations, we argue that in the convection zone one can isolate information about the equation of state which is relatively unaffected by other uncertainties in the physics of the solar interior. We review the different treatments that have been used to describe the thermodynamics of stellar plasmas. Through application of several of these to the computation of models of the solar envelope we demonstrate that the sensitivity of the observed frequencies is in fact sufficient to distinguish even quite subtle features of the physics of solar matter. This opens up the possibility of using the Sun as a laboratory for statistical mechanics, under conditions that are out of reach in a terrestrial laboratory.     

A theory of integration for the extended Delaunay method

In this paper a method for the integration of the equations of the extended Delaunay method is proposed. It is based on the equations of the characteristic curves associated with the partial differential equation of Delaunay-Poincaré. The use of the method of characteristics changes the partial differential equation for higher order approximations into a system of ordinary differential equations. The independent variable of the equations of the characteristics is used instead of the angular variables of the Jacobian methods and the averaging principle of Hori is applied to solve the equations for higher orders. It is well known that Jacobian methods applied to resonant problems generally lead to the singularity of Poincaré. In the ideal resonance problem, this singularity appears when higher order approximations of the librational motion are considered. The singularity of Poincaré is non-essential and is caused by the choice of the critical arguments as integration variables. The use of the independent variable of the equation of the characteristics in the place of the critical angles eliminates the singularity of Poincaré.     

太阳黑子月平均面积数活动周及其特征

我们对第12周至第22周的太阳黑子月平均面积数进行统计分析,并与相应的太阳黑子月平均数相比较,结果表明太阳黑子月平均面积数活动周与太阳黑子月平均数活动周有一定的关系。在多数情况下,太阳黑子出现最大值的时间与太阳黑子面积数出现最大值的时间上不一致;太阳黑子平滑月平均数活动周上升期与太阳黑子平滑月平均面积数上升期在大多数情况下不相同;太阳黑子平滑月平均数活动周平均效果的瓦德迈尔效应(Waldmeiereffect)一般要比太阳黑子平滑平均面积数的活动周明显;文中还对太阳黑子平滑月平均面积数活动周的特征进行了分析。     

A modified Oort model of an ensemble of molecular clouds in a disk galaxy

We develop a three-dimensional numerical model for an ensemble of molecular clouds moving in the fixed gravitational potential of a galaxy. This scheme is a modification of the widely known model of Oort and includes different processes of coagulation and fragmentation of clouds under pairwise collisions, interaction of clouds with the diffuse interstellar medium, and also feedback: the breaking up of clouds into small fragments under the action of stars arising in them. This model makes it possible to study the influence of various parameters of both the galaxy itself and the ensemble of molecular clouds on the process of large-scale star formation connected with giant molecular clouds and on the temporal changes of the global structure of the interstellar medium. We give as an example a computation of the evolution of the energy characteristics of an ensemble of molecular clouds in a spiral galaxy.Translated fromAstrofizika, Vol. 37, No. 4, 1994.     

Tectonic Structure,Classification, and Evolution of Arachnoids on Venus: Preliminary Results

An analysis has been done of the topography and geologic structure of arachnoids—specific radial/concentric volcannic-tectonic structures on the surface of Venus. A representative sample (53 arachnoids) from 265 structures of this type, which are listed in the catalog of volcanic structures of the surface of Venus (Crumpler and Aubele, 2000), has been studied. The overwhelming majority of arachnoids are shown to be depressions that are commonly outlined by concentric extensional structures. Following Head et al. (1992) and Aittola and Kostama (2001), the assumption is confirmed and substantiated that arachnoids are formed by gravitational relaxation of small magmatic diapirs. Several types of arachnoids are identified on the basis of an analysis of structural patterns characteristic of such structures. It is also shown that the formation of different types of arachnoids depends on the depth of the magmatic diapir under the surface, on the thickness and reologic properties of the structures superposed on the evolving magmatic diapir, and on the character of regional stress fields that arise in the process of formation of such structures. The conclusion is drawn that most of the arachnoids were formed due to the gravitational relaxation of magmatic diapirs within the brittle part of the lithosphere, and some of them appeared as a result of the gravitational relaxation of radially fractured centers—novae. It is also shown that arachnoids are long-lived and multistep structures. At least some of them began to evolve before the formation of regional plains with wrinkle ridges, and their development ended after this event.     

High-sensitivity STEP-F spectrometer-telescope for high-energy particles of the CORONAS-PHOTON satellite experiment

The STEP-F satellite telescope for measuring electrons and protons of the Photon scientific equipment is described. Its design features are given. The device detects electrons, protons, and α-particles in the energy range 0.18–2.3, 7.4–55.2, and 298–160.0 MeV, respectively. Geometric factors vary in the range of 12.4–21.7 cm² sr, depending on the energy of the particles. In addition, there are three channels of mixed recording of particles of different types and channels of recording of the secondary electromagnetic radiation generated in the construction materials of the device and spacecraft. Methods and results of the computer simulation of the passage of the particle through detector materials are presented, along with configuration, calibration measurements, and tests (both standalone and integrated) within the complex of scientific instrumentation and spacecraft. Updated data on geometric factors of the device and energy ranges of the direct detection of charged high-energy particles and of channels of mixed recording of several types of particles are given. Special software is described for the rapid analysis of the processed data of the STEP-F telescope, and the visualization of time variations of particle fluxes with different time resolution in some periods of high solar activity and in its absence.     

Dynamic Structure of the GLONASS and GPS Orbital Space: Problem of Disposal of Retired Objects

The paper presents the results of a study of the dynamic structure of the orbital space of the navigation systems GLONASS and GPS. It is shown that the dynamic structure of the GLONASS region is determined by the action of one stable Lidov–Kozai secular resonance. The motion of almost all the retired objects of the GLONASS system is stable throughout the 100-year study period. In the GPS region, there is an orbital resonance and a large number of secular resonances. Their combined influence leads to a rapid increase in the eccentricity of the orbits of the retired objects of the system. Features of the dynamic structure of the orbital space are used to find the graveyard (parking) orbits of the retired objects of navigation systems.     

大行星轨道运动与太阳黑子数的中长周期变化

本文对不同序列的太阳黑子数资料作了分析研究,计算得到了可能的太阳黑子活动的中长周期变化,并分别与由大行星轨道运动引起的日心轨道角动量变化的周期进行比较,发现二者具有比较一致的谱结构。基于本文的讨论和文[17]的结论,我们进一步认为大行星轨道运动是太阳黑子数周期性变化的可能的外部因素。     

A relativistic model of the movement of apparent superluminal radio sources

Based on the relativistic model of the apparent superluminal motion and under the condition that the center of mass of a superluminal radio source remains in motion relative to the observer, the equation of the apparent velocity between nucleus and component is derived. Assuming that the directions of jet and movement of superluminal radio source are opposite, then, supposing that the velocities of nucleus and components of SLS are equal and the nucleus is fixed, the equations of real velocity are respectively derived. With the data of V_app and θ substituted in the equation of real velocity, the velocity of the components of SLS is obtained. Comparing the real velocity with the velocity of Hubble redshift of SLS, it is concluded that the movement of SLS has no influence on the velocity of components.     

Intensity Fluctuations of Radiation Escaping from a Multicomponent Stochastic Atmosphere. I

This is the first part of a paper devoted to a theoretical investigation of intensity fluctuations of radiation at the frequencies of a spectral line formed in a multicomponent stochastic atmosphere. It is assumed that the optical depth of structural elements and the power of the energy sources contained in them undergo random variations. The frequency dependence of the relative mean-square deviation of the intensity of radiation escaping from the atmosphere is determined. Two special cases are considered and it is shown that the behavior of this quantity is different, depending on which of the indicated characteristics of the medium undergoes random variations. The results make it possible to judge the character of random variations in the fine structure of a radiating medium from observations of it in the cores and wings of spectral lines. Recent observations of prominences made using the SUMER spectrometer in the SOHO international project served as the specific motivation for the work.     

On the Formation of Planetesimals: Radial Contraction of the Dust Layer Interacting with the Protoplanetary Disk Gas

Radial contraction of the dust layer in the midplane of a gas–dust protoplanetary disk that consists of large dust aggregates is modeled. Sizes of aggregates vary from centimeters to meters assuming the monodispersion of the layer. The highly nonlinear continuity equation for the solid phase of the dust layer is solved numerically. The purpose of the study is to identify the conditions under which the solid matter is accumulated in the layer, which contributes to the formation of planetesimals as a result of gravitational instability of the dust phase of the layer. We consider the collective interaction of the layer with the surrounding gas of the protoplanetary disk: shear stresses act on the gas in the dust layer that has a higher orbital velocity than the gas outside the layer, this leads to a loss of angular momentum and a radial drift of the layer. The stress magnitude is determined by the turbulent viscosity, which is represented as the sum of the α-viscosity associated with global turbulence in the disk and the viscosity associated with turbulence that is localized in a thin equatorial region comprising the dust layer and is caused by the Kelvin–Helmholtz instability. The evaporation of water ice and the continuity of the mass flux of the nonvolatile component on the ice line is also taken into account. It is shown that the accumulation of solid matter on either side of the ice line and in other regions of the disk is determined primarily by the ratio of the radii of dust aggregates on either side of the ice line. If after the ice evaporation the sizes (or density) of dust aggregates decrease by an order of magnitude or more, the density of the solid phase of the layer’s matter in the annular zone adjacent to the ice line from the inside increases sharply. If, however, the sizes of the aggregates on the inner side of the ice line are only a few times smaller than behind the ice line, then in the same zone there is a deficit of mass at the place of the modern asteroid belt. We have obtained constraints on the parameters at which the layer compaction is possible: the global turbulence viscosity parameter (α < 10^?5), the initial radial distribution of the surface density of the dust layer, and the distribution of the gas surface density in the disk. Restrictions on the surface density depend on the size of dust aggregates. It is shown that the timescale of radial contraction of a dust layer consisting of meter-sized bodies is two orders of magnitude and that of decimeter ones, an order of magnitude greater than the timescale of the radial drift of individual particles if there is no dust layer.