排序方式： 共有166条查询结果，搜索用时 312 毫秒
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92.
C. C. Kuranz R. P. Drake T. L. Donajowski K. K. Dannenberg M. Grosskopf D. J. Kremer C. Krauland D. C. Marion H. F. Robey B. A. Remington J. F. Hansen B. E. Blue J. Knauer T. Plewa N. Hearn 《Astrophysics and Space Science》2007,307(1-3):115-119
We present data from recent high-energy-density laboratory experiments designed to explore the Rayleigh–Taylor instability
under conditions relevant to supernovae. The Omega laser is used to create a blast wave structure that is similar to that
of the explosion phase of a core-collapse supernova. An unstable interface is shocked and then decelerated by the planar blast
wave, producing Rayleigh–Taylor growth. Recent experiments were performed using dual, side-on, x-ray radiography to observe
a 3D “egg crate” mode and an imposed, longer-wavelength, sinusoidal mode as a seed perturbation. This paper explores the method
of data analysis and accurately estimating the position of important features in the data. 相似文献
93.
目前的星系形成理论认为，盘状星系由暗晕中的重子物质冷却并坍缩而成。在这一演化图像中，重子物质的角动量及其分布起着关键作用，它直接决定了盘状星系的结构。然而，在盘状星系形成和演化的各种解析、半解析模型及数值模拟中，出现了一系列与角动量有关的问题。其中包括角动量灾变(angular momentum catastrophe)及角动量分布不匹配(mismatch of angulamomentum profile)等。近年来，为解决此类问题，人们进行了大量的研究，引入并建立了各种机制和模型。详细表述了星系形成与演化中两类主要的角动量问题，并系统地综述了目前针对此类问题所提出的各种可能的解决方法和途径。 相似文献
94.
Alastair S. Moore James Lazarus Matthias Hohenberger Joseph S. Robinson Edward T. Gumbrell Mike Dunne Roland A. Smith 《Astrophysics and Space Science》2007,307(1-3):139-145
We describe experiments that investigate the capability of an experimental platform, based on laser-driven blast waves created
in a medium of atomic clusters, to produce results that can be scaled to astrophysical situations. Quantitative electron density
profiles were obtained for blast waves produced in hydrogen, argon, krypton and xenon through the interaction of a high intensity
(I ≈ 1017 Wcm−2), sub-ps laser pulse. From this we estimate the local post-shock temperature, compressibility, shock strength and adiabatic
index for each gas. Direct comparisons between blast wave structures for consistent relative gas densities were achieved through
careful gas jet parameter control. From these we investigate the applicability of different radiative and Sedov-Taylor self-similar
solutions, and therefore the (ρ,T) phase space that we can currently access. 相似文献
95.
银河系厚盘的发现，对于研究银河系以至星系的结构和演化具有重要意义。在简单回顾银河系结构研究史和厚盘发现过程的基础上，综合介绍了人们对银河系厚盘各方面性质认识的现状，并对迄今为止所提出的几种厚盘形成机制作了比较详细的说明和讨论。就目前来看，与伴星系的并合可能是形成厚盘最为可能的机制。 相似文献
96.
We interpret the observed X-ray morphology of the central part of the Crab Nebula (torus + jets) in terms of the standard theory by Kennel and Coroniti (1984). The only new element is the inclusion of anisotropy in the energy flux from the pulsar in the theory. In the standard theory of relativistic winds, the Lorentz factor of the particles in front of the shock that terminates the pulsar relativistic wind depends on the polar angle as γ = γ0 + γ m sin2 θ, where γ0∼200 and γm∼4.5×106. The plasma flow in the wind is isotropic. After the passage of the pulsar wind through the shock, the flow becomes subsonic with a roughly constant (over the plerion volume) pressure P=1/3;n∈ where n is the plasma particle density and ∈ is the mean particle energy. Since ∈∼γmc 2, a low-density region filled with the most energetic electrons is formed near the equator. A bright torus of synchrotron radiation develops here. Jet-like regions are formed along the pulsar rotation axis, where the particle density is almost four orders of magnitude higher than that in the equatorial plane, because the particle energy there is four orders of magnitude lower. The energy of these particles is too low to produce detectable synchrotron radiation. However, these quasijets become comparable in brightness to the torus if additional particle acceleration takes place in the plerion. We also present the results of our study of the hydrodynamic interaction between an anisotropic wind and the interstellar medium. We compare the calculated and observed distributions of the volume emissivity of X-ray radiation. 相似文献
97.
S. V. Bogovalov 《Astronomy Letters》2001,27(3):176-180
We study the effect of magnetic-field axial asymmetry on the magnetocentrifugal acceleration of plasma when it flows in a source’s rotating magnetosphere (propeller effect). For an axisymmetric steady plasma flow, the first corrections to the energy that arise when the source rotates slowly are proportional to Ω4, suggesting a highly inefficient plasma acceleration. Magnetic-field axial asymmetry is shown to substantially modify the acceleration. The first corrections arise even in the first order in Ω. The plasma acceleration turns out to be considerably more efficient in a nonaxisymmetric magnetic field. 相似文献
98.
Brian Warner 《Astrophysics and Space Science》1995,230(1-2):1-7
A brief overview is given of the history of astrophysics in South Africa up to the beginning of the modern era. 相似文献
99.
I. V. Panov 《Astronomy Letters》2003,29(3):163-169
The concept of the r-process path is considered from the standpoint of a dynamic model. Rapid nucleosynthesis is shown to proceed not along certain preferential lines called the r-process paths but in the region of nuclei bounded on the one side by the existing nuclei and on the other side by nuclei upon reaching which the r-process enters a cooling phase. This view is shown to account for the main heavy-element abundance patterns. 相似文献
100.
The most recent fission-barrier calculations based on improved mass formulas indicate that the adopted values are underestimated. We analyze the dependence of the fission rates on the fission barrier and show that an increase in the fission barriers leads not so much to a decrease in the importance of fission as to the possible synthesis of heavier elements in the r-process. The rates of induced fission of most isotopes with Z>80 at astrophysical energies have been calculated for the first time for fission barriers obtained from different theoretical models. 相似文献