共查询到20条相似文献，搜索用时 46 毫秒
1.
Dr. Bijan Saha PhD 《Astrophysics and Space Science》2006,302(1-4):83-91
We consider a self-consistent system of Bianchi type-I (BI) gravitational field and a binary mixture of perfect fluid and
dark energy given by a cosmological constant. The perfect fluid is chosen to be the one obeying either the usual equation
of state, i.e., p = ζ, with ζ ∊ [0, 1] or a van der Waals equation of state. Role of the Λ term in the evolution of the BI Universe has been
studied. 相似文献
2.
The differential energy spectrum and charge ratio of primary cosmic ray electrons produced by collisions of primary cosmic ray particles with the interstellar medium is calculated by means of the two temperature statistical model of high-energy interactions. Two realistic models for the primary cosmic ray flux are considered. Contributions to the primary cosmic ray electron intensity from both the pion and kaon decay modes have been included. The distribution of matter in the galaxy and energy loss of produced secondaries and electrons are considered. The results are compared to recent experimental data. 相似文献
3.
The photoelectron energy loss rate to the ambient electrons is discussed. It is shown that the conventional Butler and Buckingham expression has been incorrectly applied in photoelectron calculations. The appropriate energy loss rates are indicated. It is also shown that the geomagnetic field has little influence on the photoelectron energy loss rate. 相似文献
4.
Celestial Mechanics and Dynamical Astronomy - In previous papers of this series the stability of hierarchical many-body dynamical systems has been considered in terms of parameters which are a... 相似文献
5.
J. H. Crane M. H. Israel J. Klarmann J. F. Ormes R. J. Protheroe 《Astrophysics and Space Science》1983,94(1):211-222
The measured elemental composition of cosmic rays with charge 16≤Z≤28 as a function of atmospheric depth was compared with a propagation calculation including energy loss. The resulting composition at the top of the atmosphere has better precision than previously possible on balloon borne experiments, and agrees well with the only satellite data available in this charge range. The extrapolation method also provides checks on assumed cross-sections for interactions of cosmic rays in air. 相似文献
6.
Nonstandard theories of fundamental interactions typically predict the existence of new kinds of weakly interacting particles.
These can escape freely from stellar interiors and act as additional source of cooling. Considerable agreement of a variety
of astrophysical observations with standard physics can serve as a source of constraints on non-standard ideas. In this paper
we consider G117-B15A pulsating white dwarf for which the secular rate, at which the period of its fundamental mode increases,
has been accurately measured. This star has been claimed the most stable oscillator ever recorded in the optical band. Because
an additional channel of energy loss would speedup the cooling rate, one is able to use this stability to derive a bound on
axion mass and on theories with large extra dimensions. We also point to the possibility of using similar arguments to constrain
supersymmetric paticles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Observations of an energy-dependent asymmetry in footpoint hard X-ray emission by RHESSI for the M4.0 solar flare of 17 March
2002 allows us to probe the dynamics of particle transport with energy and time. The presence of such an asymmetry is most
readily explained by the effects of a converging magnetic field with different rates of convergence at the different footpoints,
as would be expected from realistic surface field distributions. Such a geometry has been discussed in the context of a trap-plus-precipitation
model where the transport of energetic particles in the flare is governed by the precipitation out of the coronal trap via
collisions, wave-particle interactions or some other scattering process, into the high-density chromosphere. Comparison of
RHESSI observations with a trap-plus-precipitation model allows us to use the energy dependence of the asymmetry and the observed
ratio of footpoint to coronal emission at the different energies to assess the role of the trapping in the transport of energetic
electrons and to probe the nature of the particle precipitation process inside the loss cone. 相似文献
8.
Du Jiulin 《Astrophysics and Space Science》2007,312(1-2):47-55
By a natural nonextensive generalization of the conservation of energy in the q-kinetic theory, we study the nonextensivity and the power-law distributions for the many-body systems with the self-gravitating
long-range interactions. It is shown that the power-law distributions describe the long-range nature of the interactions and
the non-local correlations within the self-gravitating system with the inhomogeneous velocity dispersion. A relation is established
between the nonextensive parameter q≠1 and the measurable quantities of the self-gravitating system: the velocity dispersion and the mass density. Correspondingly,
the nonextensive parameter q can be uniquely determined from the microscopic dynamical equation and thus the physical interpretation of q different from unity can be clearly presented. We derive a nonlinear differential equation for the radial density dependence
of the self-gravitating system with the inhomogeneous velocity dispersion, which can correctly describe the density distribution
for the dark matter in the above physical situation. We also apply this q-kinetic approach to analyze the nonextensivity of self-gravitating collisionless systems and self-gravitating gaseous dynamical
systems, giving the power-law distributions the clear physical meaning.
相似文献
9.
利用扩展的Skyrme作用可从Hartree-Fock多体理论中给出一种新的状态方程。本文在这个状态方程的基础上研究了静态中子星的性质。对于SKM和SG2这两个较好的Skyrme相互作用模型计算得到中子星的最大质量分别为Mmax=1.7M。，Max=1.67M。，此外，本文还研究了中子星的其它性质，如引力红移、惯量矩等，计算结果与观测以及Glitch模型符合。最后还发现在这种状态方程下，中子星冷却仅能通过冷却速度相对较慢的修正的Urca过程来实现。为便于比较，文中还计算了AV14＋TBF和Paris TBF这两种三体相互作用模型下的中子星的性质。 相似文献
10.
Ranjna Bakaya R. R. Rausaria P. K. Koul P. N. Khosa 《Astrophysics and Space Science》1989,151(1):103-113
Evolution of electron energy distributions have been studied by combining small-angle scattering with analytical treatment of large-angle collision using the Monte-Carlo technique. By use of these, the distributions and energy loss have been calculated as functions of column density, the heating functions have been calculated at different depths of the solar atmosphere. From the heating functions, an increase in temperature produced by the electrons at different column densities has been computed. It is found that rise in temperature increases with an increase in incident electron energy. 相似文献
11.
A Monte Carlo simulation has been carried out for URCA processes in a degenerate convective stellar core, such as would be obtained following degenerate carbon ignition. We find energy loss rates substantially less than obtained by Paczynski in his vibrational approximation for this process. We conclude that the loss rates should be computed by direct integration over the convective core assuming a uniform ratio of the abundances of the URCA pair. 相似文献
12.
Hiroyuki K.M. Tanaka 《Icarus》2007,191(2):603-615
In order to evaluate the obliquity-driven atmospheric-density path length effect on nuclide production rate on Mars, we performed a Monte-Carlo simulation to produce the number of secondary particles such as muons, neutrons and protons in the martian atmosphere and to simulate that production of 10Be and 36Cl in the martian regolith by muons and neutrons depends on how much atmosphere had been present for the past 10 million years. The vertical profile of the present martian atmosphere to generate secondary particles has been determined based on the data provided by the Viking missions. For other thickness profiles, we scaled Linsley's atmospheric model. Atmospheric shower has been generated with the SIBYLL 2.1 for high-energy hadronic interactions and EHSA for low energy photonuclear interactions. With increasing atmospheric thickness, more primary interactions occur in the atmosphere. Consequently the proton flux is reduced and the secondary cosmic ray flux, such as muons or energetic neutrons increases at surface. The result indicates that the muon production is more sensitive to obliquity-driven atmospheric variations than proton reduction. A thicker atmosphere would result in enhanced nuclide production at a place deeper than 5 m below the surface and the nuclides present in detectable concentrations. Application to the polar deposit is described. 相似文献
13.
Consideration is given to the motion of electrons in a photon field of the monoenergetic or power-law spectrum under the conditions when the main mechanism of energy loss is the inverse Compton scattering by field photons. This process changes the primary spectrum of electrons and converts low-energy field photons to high-energy gamma-quanta for which the electron confinement region is assumed to be optically thin. The electron and gamma-ray spectra have been obtained in a wide energy interval including the Klein-Nishina and Thomson regions. A simple qualitative dependence of the solutions found on the field parameters and the primary spectrum of electrons has been established.The electron and gamma-ray spectra have been obtained by numerically solving the kinetic equation dependent on two variables: the energy of electrons and their path (or the time of motion) in a photon field. The results dramatically differ from the solution of the steady-state kinetic equation which depends only on the electron energy and is frequently used in the given problem. 相似文献
14.
The ambient photoelectron spectrum above 300 km has been measured for a sample of 500 AE-E orbits during the period 13 December 1975 to 24 February 1976 corresponding to solar minimum conditions. The 24 h average and maximum ΣKp were 19 and 35, respectively. The photoelectron flux above 300 km was found to have an intensity and energy spectrum characteristic of the 250–300 km production region only when there was a low plasma density at the satellite altitude. Data taken at local times up to 3 h after sunrise were of this type and the escaping flux was observed to extend to altitudes above 900 km with very little modification, as predicted by several theoretical calculations. The flux at high altitudes was found to be extremely variable throughout the rest of the day, probably as a result of attenuation and energy loss to thermal plasma along the path of the escaping photoelectrons. This attenuation was most pronounced where the photoelectrons passed through regions of high plasma density associated with the equatorial anomaly. At altitudes of 600 km, the photoelectron fluxes ranged from severely attenuated to essentially unaltered—depending on the specific conditions, Photoelectron fluxes from conjugate regions were often less attenuated than those observed arriving from the high density regions immediately below. Comparison of the observed attenuations, photoelectron line broadening, and energy loss due to coulomb scattering from the thermal plasma with rough calculations based on stopping power and transmission coefficients of thermal plasma for fast electrons yielded order of magnitude agreement—satisfactory in view of the large number of assumptions necessary for the calculations. Overall, the impression of the high altitude photoelectron flux which emerges from this work is that the fluxes are extremely variable as a consequence of interactions with the thermal plasma whose density is in turn affected by electrodynamic and neutral wind processes in the underlying F region. 相似文献
15.
The integral flux of low energy protons (> 10 MeV) observed by the University of New Hampshire cosmic ray detector aboard the Pioneer 9 spaceprobe has been compared with similar measurements of the near-Earth spacecraft Explorer 34 during the decay phase of the February 25–March 2, 1969 series of solar cosmic ray events. At this time the Pioneer 9 spaceprobe was 0.8 AU from the Sun and close to the Sun-Earth radial line. The ratio of integral fluxes as measured by the separated spacecraft can be calculated theoretically during the convective phase of the decay of these events and will depend on whether energy loss processes are operative. A comparison of the observed and theoretically calculated ratios suggests that the adiabatic energy loss process is operative. 相似文献
16.
M. T. Crosta A. Vecchiato F. de Felice M. G. Lattanzi B. Bucciarelli 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):209-218
In this article we outline the structure of a general relativistic astrometric model which has been developed to deduce the position and proper motion of stars from 1 µarcsecond optical observations made by an astrometric satellite orbiting around the Sun. The basic assumption of our model is that the Solar System is the only source of gravity, hence we show how we modeled the satellite observations in a many-body perturbative approach limiting ourselves to the order of accuracy of (v/c)2. The microarcsecond observing scenario outlined is that for the GAIA astrometric mission. 相似文献
17.
During the decay of solar cosmic-ray events cosmic-rays with kinetic energies of about 1 MeV are convected outward with the solar wind. It is shown that, with currently available observations it should be possible to demonstrate directly the energy losses which are occurring. Observations from two spacecraft on the same heliocentric radial line are required. In this paper observations from Venera-4 and Imp-F have been used. A simple and direct demonstration would be provided by the observation of nearly mono-energetic pulses convected between the two spacecraft, but no such pulses were found to be present. A second method depends upon observing the ratio of the integral fluxes at the two spacecraft and comparing this with the value predicted by theory. The relevant theoretical analysis has been given. It is shown that in order to discriminate between energy-loss processes the spacecraft must be well separated. For spacecraft at Earth's orbit and the orbit of Venus the integral-flux ratio predicted with energy loss due to adiabatic deceleration is a factor of three higher than that predicted with no energy loss. Comparisons of integral-flux ratios for two events observed on spacecraft separated by approximately 0.1 AU gave inconclusive results. In view of the importance of energy-loss processes in the propagation of cosmic rays it is suggested that others with access to relevant data might continue this investigation. 相似文献
18.
More than a thousand interactions of primary heavy nuclei of the cosmic radiation with charge ≥10 and energy >1 GeV nucleon?1 in nuclear emulsion have been studied with emphasis on how the primary nucleus fragments. It has been determined that the cases of multiple successive fragmentations that have been observed do not occur more frequently than expected. The fragmentation ofZ>20 nuclei does depend on the target nucleus to some extent so it is important to try to separate the interactions in emulsion by theirN h (number of evaporation prongs). The fragmentation of 8 16 O at 2.1 GeV nucleon?1 measured at the Bevalac shows a similar dependence on target nucleus. By using data from these new interactions combined with published data we have simulated on a computer nuclear cascades in both emulsion and air. Results on these cascades are given for both primary silicon and primary iron nuclei. These results are used to discuss the fluctuations expected in extensive air showers produced by heavy primary nuclei. 相似文献
19.
A.J. Dessler 《Icarus》1980,44(2):291-295
Theoretical arguments have been presented to the effect that both plasma and energy are supplied to the Jovian magnetosphere primarily from internal sources. If we assume that Io is the source of plasma for the Jovian magnetosphere and that outward flow of plasma from the torus is the means of drawing from the kinetic energy of rotation of Jupiter to drive magnetospheric phenomena, we can obtain a new, independent estimate of the rate of mass injection from Io into the Io plasma torus. We explicitly assume the solar wind supplies neither plasma nor energy to the Jovian magnetosphere in significant amounts. The power expended by the Jovian magnetosphere is supplied by torus plasma falling outward through the corotational-centrifugal-potential field. A lower limit to the rate of mass injection into the torus, which on the average must equal the rate of mass loss from the torus, is therefore derivable if we adopt a value for the power expended to drive the various magnetospheric phenomena. This method yields an injection rate of at least 103 kg/sec, a value in agreement with the results obtained by two other independent methods of estimating mass injection rate. If this injection rate from Io and extraction of energy from Jupiter's kinetic energy of rotation has been maintained over geologic time, then approximately 0.1% of Io's mass (principally in the form of sulfur and oxygen) has been lost to the Jovian magnetosphere, and Jupiter's spin rate has been reduced by less than 0.1%. 相似文献
20.
The behaviour of a subsystem of a many-body problem may be studied using the hierarchical relative coordinates defined by Nugeyre and Bouvier (1981), The present article employs a notation allowing the position vectors of the particles to be expressed explicity as functions of the hierarchical relative coordinates, This machinery is used to generalize a result of Patnaik's (1975) concerning escape from a many-body system. 相似文献