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1.
从流体动力学方程出发,用微扰法得出含平流双温吸积盘的径向,环向不稳定性的色散方程,并对平流和径向粘滞力对双温吸积盘的影响进行了较详细的讨论。结果表明：平流和径向粘滞力对声模有较大的影响,且不改变粘滞模和热模的稳定性质。而环向扰动对吸积盘的各种模有着较明显的作用,这一模型有利于解释活动天体的周期和准周期光变现象。 相似文献
2.
在吸积盘内由于吸积物质的径向运动，盘内物质间沿径向的粘滞力将会对盘的性质产生一定影响．本文计算了等温吸积盘中（考虑径向粘滞力）的不稳定性问题，对所求得的色散方程的分析表明，径向粘滞力将使吸积盘趋向稳定。本文还对径向粘滞力对盘的稳定性的影响作了物理解释，并发现径向粘滞力的引入不会引入新的稳定或不稳定模式。 相似文献
3.
通过对含平流双温吸积盘的不稳定性研究 ,发现较小的平流对几何薄、辐射致冷为主的吸积盘的两个声模有较大的影响 ;并不影响几何slim、辐射致冷的吸积盘的稳定性质。同时还发现 ,当考虑环向扰动时 ,吸积盘的不稳定性质与纯径向扰动情况下有较大的区别 相似文献
4.
在吸积盘内由于吸积物质的径向运动，盘内物质间沿径向的粘滞力将会对盘的性质产生一定影响。本计算了等温吸积盘中（考虑径向粘滞力）的不稳定性问题，对所求得的色散方程的分析表明，径向粘滞力将使吸积盘趋向稳定。本还对径向粘滞力对盘的稳定性的影响作了物理解释，并发现径向粘滞力的引入不会引入新的稳定或不稳定模式。 相似文献
5.
本文从磁流体动力学方程组出发,用微扰法得出含三维磁场等温薄吸积盘的径向、轴向及环向不稳定性的色散方程．并详细讨论了磁场各分量对吸积盘不稳定性的影响．结果表明,磁场的径向和环向分量对磁声模和非轴对称模的不稳定性的增加起着主要的作用,且径向振荡大于轴向振荡．这一模型有利于解释ＦＵＯｒｉｏｎｉｓ和ＴＴａｕｒｉＳｔａｒｓ的周期光变现象 相似文献
6.
对等温,有磁薄吸积盘脉动不稳定性的多因素影响 总被引：1，自引：0，他引：1
本从磁流体动力学方程组出发，用微扰法得出等温有磁薄吸积盘径向脉动不稳定性的色散方程，详细讨论了磁场、径向粘滞力和因果性修正的α型粘滞对吸积盘不稳定性的影响。我们的结论是：磁场是一种在全盘区域起作用的非稳因素，它能影响粘滞模式的不稳定性和两种声波模式的增长率。径向粘滞力是一种在全盘区域起作致稳因素，它主要影响两种声波模式的不稳定性。α型粘滞的因果性修正主要在盘内区起作用，它对吸积盘的不稳定性影响较 相似文献
7.
含三维磁场等温薄吸积盘的振荡不稳定性 总被引：1，自引：1，他引：0
本从磁流体动力学方程组出发,用微扰法得出含三维磁场等温薄吸积盘的径向,轴向及环向不稳定性的色散方程,并详细讨论了磁场各分量对吸积盘不稳定性的影响。结果表明,磁场的径向和环向分量对磁场声模和非轴对称模的不稳定性的增加起着主要的作用,且径向振荡大于轴向振荡,这一模型有利于解释ＦＵＯｒｉｏｎｉｓ和ＴＴａｕｒｉＳｔａｒｓ的周期光变现象。 相似文献
8.
含粘滞的弱磁化吸积盘的非轴对称脉动不稳定性 总被引：1，自引：0，他引：1
本文讨论了一种含扩散型粘滞的弱磁化等温吸积盘模型．在作者原有工作的基础上研究了吸积盘对非轴对称扰动（含径向、环向和垂向三个方向的扰动）所表现的脉动不稳定性．结果表明，径向扰动是最重要、最根本的扰动：在无径向扰动时，吸积盘中不存在环向扰动与垂向扰动所产生的脉动不稳定性．在径向扰动存在时，吸积盘除了可能存在纯径向脉动不稳定性外，还可能存在由于径向扰动与垂向扰动的耦合所引起的轴对称脉动不稳定性，以及由于径向扰动与环向扰动的耦合所引起的非轴对称脉动不稳定性．当上述三个方向的扰动并存时，对应的非轴对称脉动不稳定性也可能存在． 相似文献
9.
本文从磁流体动力学方程组出发，用微扰法得出等温有磁薄吸积盘径向脉动不稳定性的色散方程，详细讨论了磁场、径向粘滞力和因果性修正的α型粘滞对吸积盘不稳定性的影响．我们的结论是：磁场是一种在全盘区域起作用的非稳因素，它能影响粘滞模式的不稳定性和两种声波模式（O－mode和Ⅰ－mode）的增长率．径向粘滞力是一种在全盘区域起作用的致稳因素，它主要影响两种声波模式的不稳定性．α型粘滞的因果性修正主要在盘内区起作用，它对吸积盘的不稳定性影响较为复杂：对粘滞模式和无磁盘的Ⅰ-mode，它表现为致稳因素，而对O－mode和有磁盘的两种声波模式，则表现为非稳因素． 相似文献
10.
含粘滞性弱磁化吸积盘的轴对称脉动不稳定性 总被引：1，自引：0，他引：1
本文讨论了一种含扩散型粘滞的弱磁化等温吸积盘模型，在此模型中研究了扩散型粘滞、垂向磁场Bz和环向磁场B对轴对称脉动不稳定性的影响．结果表明，对于轴对称扰动，一般情况下盘内存在四种轴对称振荡模式．其中二种模式是脉动不稳定的，粘滞和磁场对它们表现为非稳因素；而另外二种模式是稳定的，粘滞和磁场对它们表现为致稳因素．此外我们还注意到，Bz和B主要影响近轴向的脉动不稳定性，扩散型弱粘滞主要影响径向脉动不稳定性． 相似文献
11.
Wei-Duo Hu Daniel J. Scheeres 《天体物理学报》2008,8(1):108-118
Periodic orbits in an arbitrary 2nd degree and order uniformly rotating gravity field are studied. We investigate the four equilibrium points in this gravity field. We see that close relation exists between the stability of these equilibria and the existence and stability of their nearby periodic orbits. We check the periodic orbits with non-zero periods. In our searching procedure for these periodic orbits, we remove the two unity eigenvalues from the state transition matrix to find a robust, non-singular linear map to solve for the periodic orbits. The algorithm converges well, especially for stable periodic orbits. Using the searching procedure, which is relatively automatic, we find five basic families of periodic orbits in the rotating second degree and order gravity field for planar motion, and discuss their existence and stability at different central body rotation rates. 相似文献
12.
Periodic orbits in an arbitrary 2nd degree and order uniformly rotating gravity field are studied. We investigate the four equilibrium points in this gravity field. We see that close relation exists between the stability of these equilibria and the existence and stability of their nearby periodic orbits. We check the periodic orbits with non-zero periods. In our searching procedure for these periodic orbits, we remove the two unity eigenvalues from the state transition matrix to find a robust, non-singular linear map to solve for the periodic orbits. The algorithm converges well, especially for stable periodic orbits. Using the searching procedure, which is relatively automatic, we find five basic families of periodic orbits in the rotating second degree and order gravity field for planar motion, and discuss their existence and stability at different central body rotation rates. 相似文献
13.
K. S. Wong 《Monthly notices of the Royal Astronomical Society》2009,396(1):439-461
In this paper, we shall study the problem of stability of polar oscillations of a non-rotating Newtonian superfluid star. We find that the stability of the latter system is guaranteed by the positive definiteness of a matrix quantity. We also find conditions which characterize the occurrence of zero-frequency polar modes, which marks the onset of polar instability. We find that the negative definiteness of the mentioned matrix quantity implies instability of the system. We apply our results to show that the polar oscillations of a non-rotating Newtonian superfluid star in the zero-temperature approximation are marginally stable. 相似文献
14.
The one-dimensional non-linear equations for a viscous fluid with finite thermal conductivity are solved to get an exact solution for a steady vertical flow. The stability of such a steady flow is examined to find that the viscosity has a very pronounced stabilizing influence on convective and acoustic modes. 相似文献
15.
Ding Shi-Xue Yang Lan-Tian Wu Xue-Bing Lu Ye 《Monthly notices of the Royal Astronomical Society》2000,317(4):737-742
The radial–azimuthal instability of a hot two-temperature accretion disc with advection is examined in this paper. We find that the inclusion of very little advection has significant effects on two acoustic modes for a geometrically thin, cooling-dominated two-temperature disc, but has no effect on acoustic modes for a geometrically slim, cooling-dominated two-temperature disc. We also find that, when azimuthal perturbations are considered, the stability properties of the disc are different from those in the pure radial perturbation case. An increase of the azimuthal wavenumber will stabilize the acoustic modes but make the viscous and thermal modes more unstable for a geometrically thin, cooling-dominated two-temperature disc. It makes the thermal mode more unstable and the acoustic mode more stable, but only affects the instability of the viscous mode for short-wavelength perturbations for a geometrically slim, cooling-dominated two-temperature disc. For a geometrically slim, advection-dominated two-temperature disc, the increase of the azimuthal perturbation makes the I- and O-modes more stable and the thermal mode more unstable, but has no effect on the viscous mode. 相似文献
16.
The stability of a recently proposed general relativistic model of galaxies is studied in some detail. This model is a general relativistic version of the well-known Miyamoto–Nagai model that represents well a thick galactic disc. The stability of the disc is investigated under a general first-order perturbation keeping the space–time metric frozen (no gravitational radiation is taken into account). We find that the stability is associated with the thickness of the disc. We find that flat galaxies have more non-stable modes than the thick ones, i.e. flat galaxies have a tendency to form more complex structures like rings, bars and spiral arms. 相似文献
17.
The stability of an isothermal, magnetized and causally limited viscosity accretion disk is examined in this paper. We find that the viscous modes are always stable throughout the disk, and the magneto-acoustic modes are pulsationally unstable. The results show that the Mach numbers do effect the instabilities of the disk and the magnetic field enhances the instability property of the radial oscillation. Our results are useful for understanding the time variations of AGN. 相似文献
18.
Ashok Ambastha 《Journal of Astrophysics and Astronomy》1984,5(3):285-306
We have studied the stability of finite gaseous discs, against large-scale perturbations, under the influence of spherical,
massive haloes. A surface-density distribution consistent with the observed spiral-tracer profiles in disc galaxies is considered
for the disc. We find that growing eigenmodes with both ‘trailing’ and ‘leading’ spirals exist in ‘cold’ discs for a wide
range of values of the halo mass and its radius. The amplification rates of the unstable modes reduce as the ratio of the
mass of the halo to the mass of the disc is increased. A uniform halo is not very effective towards stabilizing the disc against
these modes. The results from the present study are consideredvis-a-vis previous studies on the global modes of self-gravitating discs. 相似文献
19.
Observations show that small-amplitude prominence oscillations are usually damped after a few periods. This phenomenon has been theoretically investigated in terms of non-ideal magnetoacoustic waves, non-adiabatic effects being the best candidates to explain the damping in the case of slow modes. We study the attenuation of non-adiabatic magnetoacoustic waves in a slab prominence embedded in the coronal medium. We assume an equilibrium configuration with a transverse magnetic field to the slab axis and investigate wave damping by thermal conduction and radiative losses. The magnetohydrodynamic equations are considered in their linearised form and terms representing thermal conduction, radiation and heating are included in the energy equation. The differential equations that govern linear slow and fast modes are numerically solved to obtain the complex oscillatory frequency and the corresponding eigenfunctions. We find that coronal thermal conduction and radiative losses from the prominence plasma reveal as the most relevant damping mechanisms. Both mechanisms govern together the attenuation of hybrid modes, whereas prominence radiation is responsible for the damping of internal modes and coronal conduction essentially dominates the attenuation of external modes. In addition, the energy transfer between the prominence and the corona caused by thermal conduction has a noticeable effect on the wave stability, radiative losses from the prominence plasma being of paramount importance for the thermal stability of fast modes. We conclude that slow modes are efficiently damped, with damping times compatible with observations. On the contrary, fast modes are less attenuated by non-adiabatic effects and their damping times are several orders of magnitude larger than those observed. The presence of the corona causes a decrease of the damping times with respect to those of an isolated prominence slab, but its effect is still insufficient to obtain damping times of the order of the period in the case of fast modes. 相似文献
20.
The stability of magnetic fields in the solar tachocline is investigated. We present stability limits for higher azimuthal wave numbers and results on the dependence of the stability on the location of toroidal magnetic fields in latitude. While the dependence of the wave number with the largest growth rate on the magnetic field strength and the magnetic Prandtl number is small, the dependence on the magnetic Reynolds number Rm indicates that lowest azimuthal modes are excited for very high Rm. Upon varying the latitudinal position of the magnetic field belts, we find slightly lower stability limits for high latitudes, and very large stability limits at latitudes below 10°, with little dependence on latitude in between. An increase of the maximum possible field was achieved by adding a poloidal field. The upper limit for the toroidal field which can be stored in the radiative tachocline is then 1000 G, compared to about 100 G for a purely toroidal field as was found in an earlier work. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献