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1.
The spiral waves in a model galaxy consisting of differentially rotating and non-rotating subsystems are considered on the basis of participating phenomena. The subsystems involved represent the Populations I and II of normal spirals, respectively. The spiral waves in such a systems are unstable in the Landau sense. Due to this instability they grow up to attain finite amplitude. This growth is stopped by a non-linear effect (the quasilinear effect), the steady state with waves of finite amplitude being established. The hypothesis is proposed that these waves should be identified with the spiral structure of the galaxies. 相似文献
2.
Bernard Shizgal 《Planetary and Space Science》1977,25(2):203-204
The validity of the Chapman-Enskog method in the calculation of the heat conductivity of the solar wind is studied. The predictions of the Chapman-Enskog theory are compared with known results of rarefied gas kinetic theory. The results suggest that the use of the Chapman-Enskog theory to describe the transport processes in the solar wind is not strictly justified. 相似文献
3.
A. M. Boichenko 《Astrophysics》2004,47(1):134-142
Observational data on the dynamics of stars in the neighborhood of the sun indicate the existence of a third integral besides the integrals of the angular momentum and energy. The Poincaré integral is proposed as a third integral. The consequences of this assumption are derived and compared with available astrophysical data. 相似文献
4.
Range of values of the Sun's mass quadrupole moment of coefficient J2 arising both from experimental and theoretical determinations enlarge across literature on two orders of magnitude, from
around 10-7 until to 10-5. The accurate knowledge of the Moon's physical librations, for which the Lunar Laser Ranging data reach an outstanding precision
level, prove to be appropriate to reduce the interval of J2 values by giving an upper bound of J2. A solar quadrupole moment as high as 1.1 10-5 given either from the upper bounds of the error bars of the observations, or from the Roche's theory, is not compatible with
the knowledge of the lunar librations accurately modeled and observed with the LLR experiment. The suitable values of J2 have to be smaller than 3.0 10-6.
As a consequence, this upper bound of 3.0 10-6 is accepted to study the impact of the Sun's quadrupole moment of mass on the dynamics of the Earth-Moon system. Such as
effect (with J2 = 5.5±1.3 × 10-6) has been already tested in 1983 by Campbell & Moffat using analytical approximate equations, and thus for the orbits of
Mercury, Venus, the Earth and Icarus. The approximate equations are no longer sufficient compared with present observational
data and exact equations are required. As if to compute the effect on the lunar librations, we have used our BJV relativistic
model of solar system integration including the spin-orbit coupled motion of the Moon. The model is solved by numerical integration.
The BJV model stems from general relativity by using the DSX formalism for purposes of celestial mechanics when it is about
to deal with a system of n extended, weakly self-gravitating, rotating and deformable bodies in mutual interactions.
The resulting effects on the orbital elements of the Earth have been computed and plotted over 160 and 1600 years. The impact
of the quadrupole moment of the Sun on the Earth's orbital motion is mainly characterized by variations of
,
, and
. As a consequence, the Sun's quadrupole moment of mass could play a sensible role over long time periods of integration of
solar system models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
耀变体(Blazars)的亮温度与黑洞喷流能量和吸积率有重要关系。搜集了53个耀变体源样本,包括22个蝎虎天体(BL Lacs)和31个平谱射电类星体(Flat Spectrum Radio Quasars,FSRQs),研究了耀变体亮温度与黑洞喷流能量的分布,并对子类中亮温度与黑洞喷流能量的相关性进行了讨论。研究结果表明:(1)蝎虎天体与平谱射电类星体的亮温度与黑洞喷流能量的分布存在明显差异,这可能与蝎虎天体与平谱射电类星体的内禀性质有关,也可能与其有无发射线及发射线的强弱有关;(2)蝎虎天体的亮温度与黑洞喷流能量之间的相关性较强,亮温度可以在一定程度上描述蝎虎天体的黑洞喷流能量,亮温度大的蝎虎天体喷流携带的能量也较大;(3)平谱射电类星体的亮温度与黑洞喷流能量之间有弱相关性,平谱射电类星体的亮温度不能清楚地描述黑洞喷流能量,黑洞喷流能量受亮温度影响较小,平谱射电类星体的黑洞喷流能量可能受到其他因素的影响;(4)耀变体的亮温度与黑洞吸积率之间有弱的相关性。 相似文献
6.
先进天基太阳天文台卫星(Advanced Space-based Solar Observatory, ASO-S)是中国科学院第2批空间科学先导专项之一,其主要目标是同时观测太阳磁场、耀斑和日冕物质抛射,并对3者之间的相互关系和内在联系进行研究.硬X射线成像仪(HXI)是ASOS卫星的3大载荷之一,它通过对太阳活动发射的硬X射线进行傅里叶调制成像,实现高空间分辨率和高时间分辨率的太阳能谱成像观测.量能器单机是HXI的关键单机之一,其主要任务是精准测量通过每对光栅后太阳硬X射线的能量和通量.主要介绍了量能器单机的工作原理及其关键指标要求、标定设备及标定方案,最后给出了标定结果,从而验证了量能器单机方案设计的合理性. 相似文献
7.
E. L. Ruskol 《Earth, Moon, and Planets》1973,6(1-2):190-201
It is suggested that the overall early melting of the lunar surface is not necessary for the explanation of facts and that
the structure of highlands is more complicated than a solidified anorthositic ‘plot’. The early heating of the interior of
the Moon up to 1000K is really needed for the subsequent thermal history with the maximum melting 3.5 × 109 yr ago, to give the observed ages for mare basalts. This may be considered as an indication that the Moon during the accumulation
retained a portion of its gravitational energy converted into heat, which may occur only at rapid processes. A rapid (t < 103 yr) accretion of the Moon from the circumterrestrial swarm of small particles would give necessary temperature, but it is
not compatible with the characteristic time 108 yr of the replenishment of this swarm which is the same as the time-scale of the accumulation of the Earth. It is shown that
there were conditions in the circumterrestial swarm for the formation at a first stage of a few large protomoons. Their number
and position is evaluated from the simple formal laws of the growth of satellites in the vicinity of a planet. Such ‘systems’
of protomoons are compared with the observed multiple systems, and the conclusion is reached that there could have been not
more than 2–3 large protomoons with the Earth. The tidal evolution of protomoon orbits was short not only for the present
value of the tidal phase-lag but also for a considerably smaller value.
The coalescence of protomoons into a single Moon had to occur before the formation of the observed relief on the Moon. If
we accept the age 3.9 × 109 yr for the excavation of the Imbrium basin and ascribe the latter to the impact of an Earth satellite, this collision had
to be roughly at 30R, whereR is the radius of the Earth, because the Moon at that time had to be somewhere at this distance. Therefore, the protomoons
had to be orbiting inside 20–25R, and their coalescence had to occur more than 4.0x109 yr ago. The energy release at coalescence is equivalent to several hundred degrees and even 1000 K. The process is very rapid
(of the order of one hour). Therefore, the model is valid for the initial conditions of the Moon. 相似文献
8.
9.
本文论述了因枢轴不规则和两个叉臂的温差引起水平轴指向漂移的影响；详细叙述了用轴准直器测定和修正这种影响的方法；并且给出了测定轴准直器参数的方法。精度估计表明，在低纬子午环上使用了电水准器和轴准直器后，对枢轴的加工精度降低了一个数量级，并且降低了对轴系稳定性的要求，然而测量和修正这些误差的精度却是很高的。 相似文献
10.
The kinematics of the outer rings and pseudorings is determined by two processes: the resonance tuning and the gas outflow.
The resonance kinematics is clearly observed in the pure rings while the kinematics of the outflow is manifested itself in
the pseudorings. The direction of systematical motions in the pure rings depends on the position angle of a point with respect
to the bar major axis and on the class of the outer ring. The direction of the radial and azimuthal components of the residual
velocities of young stars in the Perseus, Carina, and Sagittarius regions can be explained by the presence of the outer pseudoring
of class R
1
R′2 in the Galaxy. We present models which reproduce the values and directions of the residual velocities of OB-associations
in the Perseus and Sagittarius regions and also model reproducing the directions of the residual velocities in the Perseus,
Sagittarius, and Carina regions. The kinematics of the Sagittarius region accurately defines the solar position angle with
respect to the bar elongation, θ
b = 45° ± 5°. 相似文献
11.
The evolution of the orbit of the second satellite of Neptune (Nereid) on time intervals up to 500 thousand years is investigated.
The methods used by authors earlier are supplemented with the possibility of considering the influence of the attraction of
the internal satellite Triton on the evolution of the orbit of the external satellite Nereid. 相似文献
12.
P. Maltby 《Solar physics》1972,26(1):76-82
Observations of the penumbral intensity of sunspots in 13 wavelength regions are presented. In 4 wavelength regions 54 sunspots are measured. In the other wavelength regions the number of sunspots considered ranges from 3–19.The penumbral intensity alters with position within the spot. This intensity variation is found to be comparable with the change in intensity from one spot to another. The penumbral intensity is found to be independent of spot size in the sample considered.The penumbra model of Kjeldseth Moe and Maltby (1969) with = 0.055 is supported by the measurements. 相似文献
13.
We discuss the variable degree of ionizationx of a hydrogen-helium plasma in the early Universe for a quasi-static expansion in thermal equilibrium. The final equation for the degree of ionization can be reduced to a polynomial of fourth order inx with known coefficients depending on the temperature. Restricting to a pure hydrogen-plasma applied to the recombination era, where the main ionization effects are due to photo-electric and collisional processes, we study the dynamical evolution of the degree of ionization for nonstatic and nonequilibrium situations. The calculation can be reduced to a pure quadrature. In the linear case, we also calculate the rate of ionization. 相似文献
14.
F.Z. Feygin A.L. Kalisher V.A. Pilipenko O.A. Pokhotelov K. Dobeś 《Planetary and Space Science》1979,27(7):913-923
The stability of the hot plasma located at the curvilinear geomagnetic field in relation to the generation of Alfvén oscillations is investigated. A general expression for the increment is obtained. The increments for the short wavelength disturbances and special energy distribution function in a parabolic magnetic field are presented. The obtained theoretical results are used in interpreting the oscillations of the “auroral radiation” type. The polarization relations in Alfvén waves are investigated. 相似文献
15.
16.
Keizo Nishi 《Solar physics》1973,33(1):23-31
The absolute intensities and the centre-to-limb variations of the Sun at three wavelengths of 1629 Å, 1684 Å, and 1739 Å were measured by a rocket-borne spectrometer flown from the Kagoshima Space Centre on 1 September 1971. The spectrometer was a double-dispersive trichrometer, whose spectral and spatial resolutions were 8.3 Å and 1.3 respectively. The results concerning the absolute intensities were similar to those measured by the Harvard College Observatory group. The results for the centre-to-limb variation at 1629 Å and 1684 Å seem to support the HSRA model but not those at 1739 Å. 相似文献
17.
18.
E. Myles Standish Jr. 《Celestial Mechanics and Dynamical Astronomy》1976,14(4):493-498
The following question is investigated: By how much may the initial conditions of a given three-body system be varied before the subsequent evolution of the new system completely differs from that of the original? Stated somewhat differently, how big is the ‘island’ in the phase space of initial conditions throughout which the parameters describing the evolution of the systems are continuous functions of the initial conditions? The extent of one such island is determined numerically and found to be surprisingly large. It is conjectured, however, that this result is due to the fact that the corresponding systems have very short disintegration times, so that the total motion is not very complex. 相似文献
19.
The precession of a rotating charged black hole in an external magnetic field is considered. The possibility of observing the effect in black hole systems with magnetized accretion, disks is discussed. 相似文献
20.
L. S. Marochnik 《Astrophysics and Space Science》1983,89(1):61-75
The solar system's position in the Galaxy is an exclusive one, since the Sun is close to the corotation circle, which is the place where the angular velocity of the galactic differential rotation is equal to that of density waves displaying as spiral arms. Each galaxy contains only one corotation circle; therefore, it is an exceptional place. In the Galaxy, the deviation of the Sun from the corotation is very small — it is equal to ΔR/R ⊙≈0.03, where ΔR=R c ?R ⊙,R c is the corotation distance from the galactic center andR ⊙ is the Sun's distance from the galactic center. The special conditions of the Sun's position in the Galaxy explain the origin of the fundamental cosmogony timescalesT 1≈4.6×109 yr,T 2?108 yr,T 3?106 yr detected by the radioactive decay of various nuclides. The timescaleT 1 (the solar system's ‘lifetime’) is the protosolar cloud lifetime in a space between the galactic spiral arms. The timescaleT 2 is the presolar cloud lifetime in a spiral arm.T 3 is a timescale of hydrodynamical processes of a cloud-wave interaction. The possibility of the natural explanation of the cosmogony timescales by the unified process (on condition that the Sun is near the state of corotation) can become an argument in favour of the fact that the nearness to the corotation is necessary for the formation of systems similar to the Solar system. If the special position of the Sun is not incidental, then the corotation circles of our Galaxy, as well as those of other galaxies, are just regions where situations similar to ours are likely to be found. 相似文献