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1.
The diffusion of charged particles in a stochastic magnetic field (strengthB) which is superimposed on a uniform magnetic fieldB 0 k is studied. A slab model of the stochastic magnetic field is used. Many particles were released into different realizations of the magnetic field and their subsequent displacements z in the direction of the uniform magnetic field numerically computed. The particle trajectories were calculated over periods of many particle scattering times. The ensemble average was then used to find the parallel diffusion coefficient . The simulations were performed for several types of stochastic magnetic fields and for a wide range of particle gyro-radius and the parameterB/B 0. The calculations have shown that the theory of charged particle diffusion is a good approximation even when the stochastic magnetic field is of the same strength as the uniform magnetic field.  相似文献   

2.
The aim of the present paper is to find the eclipse perturbations, in the frequency-domain, of close eclipsing systems exhibiting partial eclipses.After a brief introduction, in Section 2 we shall deal with the evaluation of thea n (l) integrals for partial eclipses and give them in terms ofa 0 0 ,a 0 0 (of the associated -functions) and integrals; while Section 3 gives the eclipse perturbations arising from the tidal and rotational distortion of the two components. The are given for uniformly bright discs (h=1) as well as for linear and quadratic limb-darkening (h=2 and 3, respectively).Finally, Section 4 gives a brief discussion of the results and the way in which they can be applied to practical cases.  相似文献   

3.
It is generally believed that the only known reaction in whichC p violation definitely occurs is in the decay of the long-lived neutralK-mesonK L +–,K L 00, andK L e ±± v (Christensonet al., 1964: Sivaram, 1982). No attempt has been made to studyC p violation outside theK-system for quite a long time. Recently,C p violation effects have been reported in the hyperon decays through the reaction (Bassompierre, 1990) with asymmetry at the level of 10–3 to 10–4.In this paper we examine the possible implications of hyperon decays asymmetry in some cosmic-ray sources. We identify cosmic-ray sources where such decays can occur. The signatures for measuring these asymmetries in both the laboratory and cosmic-ray sources are examined.It is found that there is a correlation between these signatures. We conclude that hyperon decays contribute significantly toC p violation observed in cosmic-ray sources.  相似文献   

4.
The initial discovery of soft X-rays from Nova Muscae 1983 was followed by eight additional observations of the three brightest novae whose outburst stage coincided with the lifetime ofEXOSAT satellite; namely three more observations of Nova Muscae 1983, three observations of Nova Vulpeculae 1984#1 (PW Vul), and two observations of Nova Vulpeculae 1984#2. Through these observations we sampled the soft X-ray light curve of classical novae from optical maximum to 900 days after. The observations seem best explained by the constant bolometric luminosity model of a hot white dwarf remnant. Although the measurements suffer from limited statistics, very broad energy bandpass, and incomplete sampling of any single nova, their constraints on the theories of nova outburst are significant. One constraint is that the lifetime of the white dwarf remnant in Nova Muscae 1983 is 2 to 3 years, which leads to the conclusion that the burned envelope massM burn should be of the order of . The second constraint is that the maximum temperature, of the white dwarf remnant should approximately be within 200 000 K to 400 000 K. We estimate that a white dwarf remnant evolving like the central star of a planetary nebula, with core mass of 0.8 to 0.9M , core luminosity of 2×104 L , and envelope mass of 10–6 M , can explain the general characteristics of the X-ray measurements for Nova Muscae 1983. In order to have 1.1M core mass, estimated from the early observations of bolometric luminosity in the UV to infrared range, a wind withM5×10–7 M yr–1 appears to be necessary. The few observations of Nova Vulpeculae 1984 #1 and Nova Vulpeculae 1984#2, during the first year after outburst, give a risetime and intensity that is consistent with a constant bolometric luminosity model.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F. R. G., 16–19 June, 1986.  相似文献   

5.
The Chisnell-Chester-Whitham method has been used to investigate the propagation of diverging plane and cylindrical shock waves through an ideal gas in presence of a magnetic field having only constant axial and variable azimuthal components, simultaneously for both weak and strong cases. Assuming an initial density distribution 0=r –w , where is the density at the plane/axis of symmetry andw is a constant, the analytical expressions for shock velocity and shock strength have been obtained. The expressions for the pressure, the density, and the particle velocity immediately behind the shock have also been derived for both cases.  相似文献   

6.
Vibrational transition probabilities namely Franck-Condon factors and -centroids have been evaluated using an approximate analytical method for theA-X systems of OH and PN. KKRV potential energy curves forX 2 i ,X 1+,A 2+, andA 1 states of OH and PN have been constructed using the latest spectroscopic data. The value of -centroids for the band have been found to increase linearly with the corresponding wavelengths. We show results for six new bands and OH and eight new bands of PN in the spectra of astronomical objects.  相似文献   

7.
The propagation of linear sound and thermal waves in a reacting fluid, in which the heating and cooling processes can be represented by a heat-loss functionL(, T, is studied. A complex dispersion relation is found, from which the phase velocity and the scale length for damping (or amplification), of the above two-wave mode are calculated Wave amplification may occur in reacting locally stable fluids. Results are applied to a hydrogen plasma model assumed to be heated at a non-specified constant rate and cooled by recombination, excitation, and ionization by collisions, and free-free transitions. The phase velocity , the scale-length for damping , and the relevant relaxation times are calculated as functions of the dimensionless frequency , for temperatures ranging from those at which the hydrogen plasma is neutral to those at which it becomes completely ionized.  相似文献   

8.
Analytical techniques are employed to demonstrate certain invariant properties of families of moon-to-earth trajectories. The analytical expressions which demonstrate these properties have been derived from an earlier analytical solution of the restricted three-body problem which was developed by the method of matched asymptotic expansions. These expressions are given explicitly to orderµ 1/2 where is the dimensionless mass of the moon. It is also shown that the inclusion of higher order corrections does not affect the nature of the invariant properties but only increases the accuracy of the analytic expressions.The results are compared with the work of Hoelker, Braud, and Herring who first discovered invariant properties of earth-to-moon trajectories by exact numerical integration of the equations of motion. (Similar properties for moon-to-earth trajectories follow from the principle of reflection). In each instance the analytical expressions result in properties which are equivalent, to orderµ 1/2, with those found by numerical integration. Some quantitative comparisons are presented which show the analytical expressions to be quite accurate for calculating particular geometrical characteristics.

Nomenclature

Orbital Elements near the Moon energy - angular momentum - semi-major axis - eccentricity - inclination - argument of node - argument of pericynthion Orbital Elements near the Earth h e energy - l e angular momentum - i inclination - argument of node - argument of perigee - t f time of flight Other symbols parameters used in matehing - U a function of the energy near the earth - a function of the angular momentum near the earth - r p perigee radius - perincynthion radius - radius at node near moon - true anomaly of node near moon - initial angle between node near moon and earth-moon line - a function ofU, , andi - earth phase angle - dimensionless mass of the moon - U 0, U1 U=U 0+U 1 - i 0, i1/2, i1 i=i 0+µ 1/2 i 1/2+µ i 1 - 0, 1/2, 1 = 0+µ 1/2 i 1/2+µ i 1 - p longitude of vertex line - n latitude of vertex line - R o ,S o ,N o functions ofU 0 and - a function ofU 0, and   相似文献   

9.
The relative abundances of cool neutral hydrogen, carbon monoxide and formaldehyde are studied using all the available observational data in the literature. The obtained mean valuesN H 1/ ,N H 1/N CO,N CO/ are approximately constant in the dark clouds of the solar neighbourhood and in the distant molecular clouds.The observed correlationsN CO,A v and ,A v show that formaldehyde can also be used as an indicator of molecular hydrogen. The ratioN H1/A v depends on densities and decays considerably in the ranges of visual absorptions in which the molecules become detectable (A v 2 mg); an average of /N H 110 is calculated for the dense dark clouds.Indications of systematic temperature gradiens T/A v are found for formaldehyde and neutral hydrogen inside the dark clouds, and qualitative comparisons are made with theoretical quantum mechanics calculations.The observed carbon monoxide and formaldehyde abundances, the free electron layer in the Galaxy, the distribution of neutral hydrogen in different states are only compatible if an ionization rate of 10–16 is accepted, provided presumably by 2 MeV protons of cosmic radiation.Three main states for neutral hydrogen and dust are identified from different kinds of observational data (21 cm line in emission, absorption in galactic radio sources and self-absorption in the hot gas background): (1) a homogeneous intercloud stratum of tenuous gas and dust with a galactic halfwidth of 350 pc and mean parametersn H=0.2 atom cm–3, spin temperatureT s 10000 K andn d 0.3 mg kpc–1; (2) cool gas and dust concentrated in spiral features with a galactic half-width of less than 100 pc, probably forming clouds with diffuse and indefinite limits, with mean parametersn H2 atom cm–3,T s <1100 K (probable average,T s =135 K) andn d 3 mg kpc–1; (3) dense gas and dust clouds with a mean diameter of 7 pc and mean parametersn H700 atom cm–3 (90% in a molecular state),T s 63 K andn d 1 mg pc–1 on which molecules as CO and H2CO are formed.The application of the Jeans criteria for gravitational instability shows that the dense clouds are gravitationally bound while the gas in the intermediate state (2) can be protected against collapse by the total internal energy in the medium increasing due to cosmic rays and the magnetic field in the Galaxy.The observed velocity halfwidths and galacticZ-halfwidths in states (1) and (2) are compatible with a total mass density in the galactic layer of 90M pc–2 (gas plus stars) according to the barometric equation.The relative abundancesN H 1/N CO, calculated from C12O and C13O data and comparisons with studies in the 21 cm emission line, show that the antenna temperatureT A + in the 2.6 mm line of C12O is a good indicator of the cool gas densities in the Galaxy. The possible application of this for studies in galactic structure is discussed and hypothetical distributions of carbon monoxide in the zones outside the galactic planeB=0° are presented.From a synthesis based on the results obtained, a cycle is postulated for the neutral hydrogen in the Galaxy: condensation and cooling of gas molecular formation gravitational collapse and star formation gas dissipation and heating by cosmic rays and UV radiation.  相似文献   

10.
The red shift and central intensity are given for eleven spectral lines having an observed reduced equivalent widthV ranging fromV=15 toV=200. The computations have been repeated for eight values of the scattering thickness of the chromosphere, from to . A theoretical interpretation of measurements in the Sun is also given.  相似文献   

11.
An exact analysis of Stokes' problem for an infinite vertical plate, whose temperature varies linearly with time, has been presented. It is observed that the velocity near the plate increases with the timet, and the Grashof numberGr. The skin-friction has been found to vary ast 7/2 and the Nusselt number varies as or whereP is the Prandtl number.  相似文献   

12.
Two-dimensional unsteady free convection and mass transfer, flow of an incompressible viscous dissipative and electrically conducting fluid, past an infinite, vertical porous plate, is considered, when the flow, is subjected in the action of uniform transverse magnetic field. The magnetic Reynolds number is taken to be small enough so that the induced magnetic field is negligible. The solution of the problem is obtained in the form of power series of Eckert numberE, which is very small for incompressible fluids. Analytical expressions for the velocity field and temperature field are given, as well as for the skin friction and the rate of heat transfer for the case of the mean steady flow and for the unsteady one. The influence of the magnetic parameter,M, modified Grashof numberG c , Schmidt numberS c and frequency , on the flow field, is discussed with the help of graphs, when the plate is being cooled, by the free convection currents (G r ,E>0), or heated (G r ,E<0). A comparative study with hydrodynamic case (M=0) and the hydromagnetic one (M0) is also made whenever necessary.List of symbols B0 applied magnetic field - |B| amplitude of the skin friction - C concentration inside the boundary layer - C concentration in the free stream - C w concentration at the porous plate - C p specific heat at constant pressure - D diffusion coefficient - E Eckert number - g x acceleration due to gravity - G c modified Grashof number - G r Grashof number - M magnetic parameter - N u Nusselt number - P Prandtl number - |Q| amplitude of the rate of heat transfer - S c Schmidt number - T temperature of the fluid - T w temperature of the plate - T temperature of the fluid in the free stream - T r ,T i fluctuating parts of the temperature profile - u, v velocity components in thex, y directions - u dimensionless velocity in thex direction - u 0 mean steady velocity - u 1 unsteady part of the velocity - u r ,u i fluctuating parts of the velocity profile - U dimensionless free stream volocity - U 0 mean free stream velocity - v 0 suction velocity - x, y co-rodinate system Greek Symbols phase angle of the skin-friction - coefficient of volume expansion - * coefficient of expansion with concentration - phase angle of the rate of heat transfer - dimensionless co-ordinate normal to the plate - dimensionless temperature - 0 mean steady temperature - 1 unsteady part of temperature - k thermal conductivity - v kinematic viscocity - density of fluid in the boundary layer - density of fluid in the free stream - electrical conductivity of the fluid - skin friction - 0 mean skin friction - frequency - dimensionless frequency  相似文献   

13.
Both the critical content c ( N m /N B , whereN m ,N B are the total numbers of monopoles and nucleons, respectively, contained in the object), and the saturation content s of monopoles in a rotating relativistic object are found in this paper. The results are:
  相似文献   

14.
In this paper a simple model of chemical evolution is proposed, according to which active phases of star formation occured, each followed by a quiescent phase where the formation of stars withm1m was totally inhibited. The contraction of the gaseous component of the system was not stopped during quiescent phases, according to observed distributions of chemical and dynamical parameters in objects of different populations. Building up a detailed model we assume that: (i) star formation is inhibited during a given active phase, at a rate which is connected to the number of supernovae born at that time; (ii) total mass is conserved in the unit comoving volume; (iii) instantaneous recycling approximation holds. According to these hypothesis, theoretical metal abundance distributions as function of a single parameter may be derived and then compared with empirical distributions related to different kinds of populations. It is found that theoretical curves systematically overestimate the objects of lower metallicity and underestimate the objects of higher metallicity in respect to observations, as a possible consequence of the last two assumptions reported above. If we leave the detailed explanation of this effect to more refined models and taking other observational data into account, the chemical evolution of both Galactic spheroid component and solar neighbourhood may be derived and the results are to be considered as essentially qualitative. If three active phases of star formation occurred during the history of the Galactic spheroid component, the yield of metals, , had to increase passing from an active phase to the next even if (metal content) and the disk mass fraction,R D, had not to exceed a value of about 0.4 when is assumed as a characteristic value for the disk component and the main part of this last is thought to have formed at the end of the second active phase. If a single active (and no quiescent) phase occurred during the history of the solar neighbourhood, the yield did not increase appreciably up to to-day and no more than half (if any) of the initial mass could escape from the system in form of galactic wind. A disk mass fractionR D0.2 is further derived, if a birth-rate stellar function smoothly dependent on the gas mass fraction and a ratio of mean past to present star formation rate of the order of unity are to be reproduced, in agreement with recent observations.  相似文献   

15.
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16.
We investigate static, spherical configurations of cold catalized matter in the Einstein-Cartan theory of gravitation. Assuming that density of spin is proportional to the number density of baryonsn and using an equation of state of a degenerate, relativistic Fermi gas, we numerically integrated the relativistic equation of equilibrium. We have also studied the stability of those configurations. Configurations with central number densityn c such that where is the effective pressure, are very similar to general relativistic configurations with the same central density. In the Einstein-Cartan theory there exists another disjoint family of equilibrium configurations for which but . Those configurations have very small masses 10–6 g and raddi 10–34 cm and are unstable.Supported in part by Research Grant MR-I-7.  相似文献   

17.
Stabiliity is applied to characterize type of motion in which the moving body is confined to certain limited regions and in this sense we may say that the motion of the body in question is stable. This method has been used in the past chiefly in connection with the classical restricted problem of three bodies.In this paper we consider a dynamical system defined by the Lagrangian
  相似文献   

18.
A simple reticle with parallel equally spaced lines to transmit light in an autometric gyro is shown to give a signal which can be used for very accurate angular precession measurements. Frequency analysis of the signal is chosen over time domain analysis and/or over a specially designed reticle.Gyro precession will induce a change in the interference structure of the spectrum in addition to dilating the overall frequency distribution. The expected output spectrum has been analytically determined, exhibiting the dependence on spot and reticle line cross sections and line spacing so that they can be precisely determined from the output data.The spectrum structure is extremely sensitive to precession. Computer simulations indicate that accuracy will be limited by reticle line spacing variations to ±4×10–9 rad. This would allow a Lense-Thirring precession measurement accurate to ±20% in 30 days (accuracy being limited by physical effects common to all such experiments) or a ±1% de Sitter precession measurement in four days.Nomenclature a n() Fourier coefficients ofI() - a n r () rapidly varying part ofa n() - a m x ,b m x Fourier coefficients ofI(x) - a (),b () Fourier sine and cosine transforms of x(x) - angle between star and gyro spin axis - 0 initial alignment angle - f focal length of optical system - I transmitted light intensity, signal function - l reticle line width - r distance from light spot center - R light-circle radius - = reduced light-circle radius - 0 reduced reticle center-spin center offset - s reticle line space - T(x) reticle transmission function - angle of gyro rotation - w g gyro angular velocity This work was supported by the M.I.T. Center for Space Research under NASA Grant NGL-22-009-019.  相似文献   

19.
The motion of spin particles in the Schwarzschild field is examined in this paper. It is shown that Mathisson-Papapetrou equations under additional conditions , where is the Lie derivative of the Killing vector j , permit only radial motion, motion in the equatorial plane and in the equilibrium points. All these types of motion are considered more in detail.  相似文献   

20.
For the theory described by the action and taking the FRW flat space metric we find an exact non-singular de Sitter model universe exp(t 2), with . It is also proved that the standard general relativity de Sitter cosmology , >0 is also a model of this higher derivative theory of gravity. If the metric is conformally flatS could describe a consistent quantum theory and its classical solutions would correspond to cosmological models in this theory.This work was supported in part by CONACYT grand P228CCOX891723, and DGICSA SEP grant C90-03-0347.  相似文献   

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