共查询到20条相似文献，搜索用时 968 毫秒
1.
Hanna A. Sabat 《Astrophysics and Space Science》2000,273(1-4):141-153
In this paper, we highlight the significance of astrophysical dataarchives, and the great opprtunities they are offering for researchersin general, and those in the developing countries in particular. Wefocus on high energy astrophysical data archives, taking RXTE as a casestudy, where we give a brief introduction to this satellite and itsinstrumentation. Then we explain in certain detail the processes ofsearch and retrieval of RXTE's archival data, finally touching verybriefly upon its data analysis. 相似文献
2.
In this paper we present several magneto-hydrostatic equilibrium models for prominences with fibril-like fine structure. For all the models ad hoc temperature profiles are used without discussing the energetics. For our models we assume fine structure to occur either across the prominence axis or along it. This approach is intended as a first step towards more realistic models based upon a series of vertical fibril structures. 相似文献
3.
The aim of this paper is to investigate the thermal stability of a fluid layer with permeable boundaries and a variable gravitational field. It is observed that the principle of exchange of stabilities is valid when the layer is heated form below and the complex growth rate of an arbitrary oscillatory mode exists outside of a circle whose radius depends upon the permeability parameter, Prandtl number and wavelength of the mode. In the case of a layer heated from below, gravity increasing upward has a destabilizing effect whereas the permeability parameter has a stabilizing effect. 相似文献
4.
Uniformly Redundant Arrays (URA's) are two–dimensional binary arrays with constant sidelobes of their periodic autocorrelation function. They are widely agreed upon to be optimum mask patterns for coded aperture imaging, particularly in imaging systems with a cyclic coded mask. In this paper, a survey of all currently known construction methods for URA's is given and the sizes and open fractions of the arrays resulting from each construction method are pointed out. Alternatives to URA's for situations in which a URA does not exist, are discussed. 相似文献
5.
J. Gay J. -L. Falin J. Kovalevsky J. -P. Corteggiani M. -T. Dumoulin 《Earth, Moon, and Planets》1980,23(2):213-230
The purpose of this paper is to propose a numerical model representing the brightness temperature of ten selected sites of the Moon as measured in CERGA. A theoretical approach is proposed in which the temperature is expressed as a function of the local zenith distance of the Sun and a quantity depending upon the local zenith distance of the observer and the difference of their azimuths. The coefficients of this expression depend upon various integrals involving frequency function of the slopes of the lunar surface. The shadows are being qualitatively taken care of by introducing the phase angle .Using the observations, the most important coefficients of the formulae have been determined. The individual measurements are represented to about 2°.2. In the mean, the model seems to have an accuracy of about 1°, this number being confirmed by observations by the satellite METEOSAT.Finally, we give a tentative frequency function of the lunar slopes that is consitent with the temperature model. 相似文献
6.
Oyama Koh-Ichiro 《Planetary and Space Science》1976,24(2):183-190
The first part of this paper uses a contamination layer model to discuss the effects of electrode contamination upon electron temperatures estimated from Langmuir probe measurements. The model assumes that the contamination layer is equivalent to a parallel capacitor and resistor. It predicts two main features associated with electrode contamination. One of them, the so-called “frequency dependence,” concerns the sweep-rate of the probe voltage and is well understood. The other is that the effect of a contaminated electrode is decreased as the density of the ambient plasma is decreased and this will be called “density dependence.” We present several experimental results which verify the above predictions.This paper also presents some other experimental results which may be useful in improving the accuracy of Langmuir probe measurements.Finally the effects of electrode contamination upon electron density estimates and energy distribution measurements are briefly discussed. 相似文献
7.
Diego F. Torres Thomas M. Dame Gustavo E. Romero 《Astrophysics and Space Science》2005,297(1-4):393-398
In this paper we briefly comment on the observational status of the possible physical association between unidentified EGRET
sources and supernova remnants (SNRs) in our Galaxy. We draw upon recent results presented in the review by Torres et al.
(2003), concerning molecular gas in the vicinity of all 19 SNRs found to be positionally coincident with EGRET sources at
low Galactic latitudes. In addition, we present new results regarding the supernova remnant CTA 1. Our findings disfavor the
possibility of a physical connection with the nearby (in projection) EGRET source. There remains possible, however, that the
compact object produced in the supernova explosion be related with the observed γ-ray flux. 相似文献
8.
The shock waves and the magnetic field in the corona above the active region on February 17–28, 1969
Irena Garczyńska 《Solar physics》1977,51(1):131-141
In this paper the situation above the large active region which passed across the solar disc between February 17 and 28, 1969 is considered. Five dynamical spectra of type II radio bursts registered by CSIRO and by Weissenau Observatory were used. After the elaboration of dynamical spectra, the parameters of shock waves and the values of magnetic field in corona were determined. The magnetic field was obtained using two methods. In the first method the connection between the velocity of shock front and the velocity of the Alfvén waves was used. In the second method the dependence of the frequency split upon the value of the magnetic field was applied. 相似文献
9.
R.H. Bishop 《Planetary and Space Science》1973,21(7):1262-1267
In an effort to determine electron density and temperature from RF impedance probe measurements, Bishop and Baker (1972) derived an expression using a quasi-static approximation for the impedance of an electrically short cylindrical antenna in a warm magnetoplasma. The problem was limited to the case where the longitudinal axis of the antenna was aligned with the magnetic field. It is the purpose of this paper to remove this restriction on the orientation angle of the antenna by using a perturbation technique valid when either ω or ν is much larger than the electron gyrofrequency. Under these conditions it is found that the antenna impedance has no dependence upon the antenna orientation angle. Although still somewhat restrictive, this result is useful for the whole class of RF probes in which the driving frequency is well above the upper hybrid resonance frequency. 相似文献
10.
Dang-Bo Liu Ai-Fang Yuan Xian-Ru Meng Luo-Bu Danzeng Jun-Han You 《Chinese Astronomy and Astrophysics》2010
When the thermal relativistic electrons with isotropic distribution of velocities move through a dense gas region or impinge upon the surface of a cloud of dense gas, the Cerenkov effect will produce peculiar atomic or ionic emission lines, which we call the “Cerenkov line-like radiation”. This prediction has been verified by the laboratory experiments in optical waveband. In this paper, the importance of the Cerenkov line-like radiation in the exploration of broad emission lines in quasars and Syf1 s is pointed out. By using this mechanism, some long standing and significant puzzles in the study of quasars could be solved. Furthermore, the magnitude orders of energy losses of various effects of a relativistic electron in cosmic gas are estimated and compared with each other to prove the effectiveness of this new mechanism in quasars. 相似文献
11.
着重评述了含激波吸积理论的发展历史和研究现状, 介绍了在伪牛顿势以及严格广义相对论框架下, 对等温和绝热两种不同的流体模型中可能发生的Ｒ－ Ｈ 激波、等温激波等各种不同激波的解析和数值模拟研究, 包括激波发生的参数空间、不同流体参数（ 比能量和比角动量） 下激波发生的位置、强度以及耗散的能量。这些研究结果表明, 在理想流体近似下, 黑洞吸积流中必定会产生激波。此外, 还介绍了含激波吸积理论在活动星系核方面的应用。对黑洞吸积理论简单讨论, 评述了含激波吸积理论与ＡＤＡＦ 吸积理论的关系, 着重评述了目前对于ＡＤＡＦ 中是否会发生激波这一存在很大争议的问题。 相似文献
12.
M. M. Jarad 《Astrophysics and Space Science》1987,139(1):83-91
Extensive radial velocity investigation has been presented in this paper for the bright Be star HR 1910, based upon thirty-three spectrograms. The analysis of these radial velocity measurments has demonstrated clearly the binary nature of the star and new orbital elements were determined. A brief discussion of the previous work on this system appears in the relevant sections. 相似文献
13.
当具有各向同性速度分布的相对论电子穿过稠密气体区,或者轰击稠密气体区的表面时,切仑科夫效应将会产生1种特殊的原子或离子发射线,称做切仑科夫线状发射.这一预言在光学波段已由实验室的实验所证实.研究指出了切仑科夫线状辐射在类星体和赛弗特1星系的宽发射线研究中的重要性,利用此新机制有可能解决类星体研究中的一些重大且长期没有解决的疑惑.例如宽氢线之间存在的反常强度比,特别是反常Lyα/Lyβ强度比的问题.并且进一步估计了相对论电子穿过宇宙气体时所产生的各种效应的能耗的数量级,并对各种能耗进行比较,证实了切仑科夫线状发射机制在类星体和塞弗特1型星系中的有效性. 相似文献
14.
A. A. Deshpande & R. Ramachandran 《Monthly notices of the Royal Astronomical Society》1998,300(2):577-582
In this paper we propose a scenario for the formation of a population of baryon-rich, dark-matter-deficient dwarf galaxies at high redshift from the mass swept out in the intergalactic medium (IGM) by energetic outflows from luminous quasars. We predict the intrinsic properties of these galaxies, and examine the prospects for their observational detection in the optical, X-ray and radio wavebands. Detectable thermal Sunyaev–Zel'dovich decrements on arcminute scales in the cosmic microwave background radiation maps are expected during the shock-heated expanding phase from these hot bubbles. We conclude that the optimal detection strategy for these dwarfs is via narrow-band Lyman-α imaging of regions around high-redshift quasars. A scaled-down (in the energetics) version of the same model is speculated upon as a possible mechanism for forming pre-galactic globular clusters. 相似文献
15.
Ritabrata Biswas Nairwita Mazumder Subenoy Chakraborty 《Astrophysics and Space Science》2011,335(2):603-609
In this paper we deal with accretion of dark energy in the holographic dark energy model for a general non-rotating static
spherically symmetric black hole. The mass of the black hole increases or decreases depending on the nature of the holographic
dark energy (quintessence or phantom) as well as on some integration parameters. It is to be illustrated that the enhancement
or reduction of mass of a black hole is independent of the mass or size of the black hole itself. Rather it depends only upon
the radius of the event horizon of the universe. Finally, the generalized second law of thermodynamics has been studied on
the event horizon to be assured that the law holds even if when the black hole mass is decreasing though it is engrossing
some mass. 相似文献
16.
A non-steady, two-dimensional, compressible mathematical model of a fluid with constant viscosity and thermal conductivity is given in order to represent a thin atmospheric layer located at 60 km height, as a function of a known initial vertical distribution of temperature, chemical concentrations of minor components and assumed free boundary conditions.The purpose of this paper is to determine the influence of convective laminar processes in the vertical distribution of minor constituents in a thermal interface. Only three minor components are considered, atomic oxygen, molecular oxygen and ozone. Numerical solutions of the stated timedependent convection problem for different Rayleigh numbers show a marked influence of the established flow pattern upon the distribution of minor constituents. In all cases, an enhancement of mean concentration gradients in relatively small regions adjacent to the warmer and colder boundaries was observed. 相似文献
17.
The HEOS detector measures the mass and speed of micrometeoroids in the Earth-Moon system. They are detected by the plasma produced by particle impacts on the sensor. During 2 yr of data collection 384 particles have been registered. As shown earlier (COSPAR 1973), they can be divided into 3 categories according to their temporal distribution: particles that are (1) randomly distributed or (2) appear in “groups” or (3) appear in “swarms” In this paper the origin of the groups and swarms is discussed. For this purpose the article orbits with respect to the Earth and the Moon were traced back. The results imply a lunar origin of the groups, whereas the swarms are correlated with the vicinity of the Earth. In addition, the dependence of the cumulative flux upon the detector's viewing direction indicates clearly an anisotropic particle flux. 相似文献
18.
The dynamic behavior of a small tri-axial body acted upon by the Newtonian forces of N major bodies of spherical symmetry
which forma planar ring configuration is studied in this paper. The equations of the translational-rotational motion of the
minor body are derived and its equilibrium states as well as their stability are investigated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
The Lie transform method used in Perturbation Theory is based upon an intrinsic algorithm for transforming functions or vector fields by a transformation close to the identity. It can thus be viewed as a specialization of methods and results of differential geometry as is shown in the first part of this paper. In a second part we answer some of the questions left open in connection with the equivalence of the algorithms proposed by Hori and Deprit. From a formal point of view, the methods are shown to be equivalent for non-canonical as well as canonical transformations and a formula relating directly the two generating functions (or vector fields) is presented (formula (5.17)). On the other hand, the equivalence is shown to hold also in the ring ofp-differentiable functions. 相似文献