共查询到20条相似文献，搜索用时 125 毫秒
1.
By considering the consecutive effects of synchrotron reabsorption, Compton scattering and other kinds of energy losses of relativistic electrons, it may be possibile to form a universal distribution of electrons in the region of reabsorption (synchrotron reactor). This will be either a power law with a power index of the energy spectrumn
r=3–5, or a relativistic Maxwell distribution with an electron temperatureT
e=4T
b(1+), where is the ratio of Compton (or other losses) to synchrotron losses, andT
bis the brightness temperature of the radiation. Since the total energy losses of electrons in the reactor is equal to zero, this ensures the continuous existence and accumulation of relativistic electrons in the region of reabsorption and their associated hard scattered radiation. Multiple Compton scattering produces a specific stepped power distribution of scattered radiation by which we can identify the reactor. In the nuclei of quasars W
Hand, therefore,n
r=3; hence the spectral index of scattered radiation in the corresponding ranges (optical, UV, X- and -ray) is
.Consideration of other kinds of losses and gains of energy by electrons can lead to the dependencen
=3–5(E) — where (E) may have either positive or negative values—which, in turn, leads to the frequency dependence of the spectral index of scattered radiation
= 1 – (), |()| < 1, |(E)| < 1.Within the framework of the model being considered, the physical parameters of the nucleus of quasar 3C 273 are calculated. 相似文献
2.
An exact analysis of the effects of mass transfer on the flow of a viscous incompressible fluid past an uniformly accelerated vertical porous and non-porous plate has been presented on taking into account the free convection currents. The results are discussed with the effects of the Grashof number Gr, the modified Grashof number Sc, the Schmidt number Sc, and the suction parametera for Pr (the Prandtl number)=0.71 representating air at 20°C.Nomenclature
a
suction parameter
-
C
species concentration
-
C
species concentration at the free stream
-
g
acceleration due gravity
- Gc
modified Grashof number (vg*(C
–C
)/U
0
3
)
- Pr
Prandtl number (C
p/K)
-
T
temperature of the fluid near the plate
-
T
dimensionless temperature near the plate ((T-T
)/(T
-T
))
-
U(t)
dimensionless velocity of the plate (U/U
0)
-
v
normal velocity component
-
v
0
suction/injection velocity
-
x, y
coordinate along and normal to the plate
-
v
kinematic viscosity (/gr)
-
C
p
specific heat at constant pressure
-
C
w
species concentration at the plate
-
C
non-dimensional species concentration ((C-C
)/(C
w
-C
))
- Gr
Grashof number (g(T
w
-T
)/U
0
3
)
-
D
chemical molecular diffusivity
- K
thermal conductivity
- Sc
Schmidt number (/D)
-
T
w
temperature of the plate
-
T
free stream temperature
-
t
time variable
-
t
dimensionless time (tU
0
2
/)
-
U
0
reference velocity
-
u
velocity of the fluid near the plate
-
u
non-dimensional velocity (u/U
0)
-
v
dimensionless velocity (v/U
0)
-
v
0
non-dimensionalv
0
(v
0
/U0)=–at–1/2
-
y
dimensionless ordinate (yU
0/)
-
density of the fluid
-
coefficient of viscosity 相似文献
3.
We compare microphotometer intensity traces perpendicular to dispersion in simultaneous spectrograms of good spatial resolution traced at various 's in each of the lines. Cross correlations between the different traces show the following: (a) For each
K there is a corresponding
b
1at which the coefficient of correlation, r, is a maximum, usually > 0.8. (b) No such high correlations are found between H and H. (c) Comparison of traces in the continuum and at all observed 's in K, H, b1, b2 show a range of 's in each line over which r is very significantly negative, while H shows no such peculiarity. 相似文献
4.
On the basis of the erenkov line emission theory in the optically thick case, a new interpretation of intensity ratios H/H and H/H in broad-line radio-galaxies (BLRGs) is reported. Calculation shows that if the theoretical ratio H/H is just taken to be the mean observed value 0.21, equivalently, the parameterX(H)=3.0, then the expected ratio H/H=6.70 is almost the same as the observations. By comparing these values with the previous investigations of QSOs (X(H)=20.9), we conclude that the number density of neutral hydrogen gas in BLRGs is almost one order-of-magnitude smaller than that in the QSOs.Preliminary verification of the erenkov line emission has been obtained by Xuet al. (1981) in the laboratory. 相似文献
5.
P. S. Goraya 《Astrophysics and Space Science》1981,78(2):419-425
The photoelectric spectrophotometric scans of the Be stars Gem, Ori, Mon and CMa have been analyzed to find out few stellar parameters. The absolute energy distributions of these stars in the wavelength range 350–750 nm have been given. Their effective temperatures and gravities have been estimated from comparisons with non-LTE model atmospheres. The stars Gem and Mon have been found to have Balmer discontinuities in emission. The excess emission in the region 620–750 nm has been observed for Mon and CMa. The evolutionary aspects of these stars are discussed and their masses have been estimated. 相似文献
6.
Horacio A. Dottori 《Astrophysics and Space Science》1981,80(2):267-280
The synthetic equivalent width (W
H) of the line H in emission is obtained for Hii regions opaque to the Lyman photon flux, with embedded OB associations with different initial chemical compositions and initial mass functions. The variation ofW
H as a function of the evolution of the ionizing stars is analysed. The observations ofW
H for M33, M101, and M51 by Searle (1971) are discussed. 相似文献
7.
We consider that single loop flares can be caused by the rotation of loop footpoints. Choosing a typical geometry for this case we find from MHD equations self-consistent expressions and a set equations governing behaviour of all physical quantities. Numerical simulations have revealed that under the determined conditions for the initial azimuthal velocity and current the pinch instability takes place. The most important parameters of the problem are the plasma and the ratio of the initial values of longitudinal and poloidal components of the magnetic field-B
1. Thus, calculations show that the critical pinch time increases with the increase ofB
1 and decreases with the increase of plasma . So the most effective flares are probable for the most high loops with strong currents. ForB
1=10 and =0.01 the critical pinch time is 2.5 s. The critical twist angle for magnetic field depends on the initial one. For low intial twist which corresponds to bigB
1 the critical one is more less. For exampleB
1=30 gives 1.8 (when ratio of loop length and radius is 10). Geometrical analysis shows that the present model can explain (for high photospheric rotation) single loop flares taking place on different parts of the loop as on the top of it as closer to one of the footpoints. It depends on the relative rotation momentum of loop footpoints. Subject headings: MHD-Sun:flares. 相似文献
8.
In this paper, we present a model of the plasma beta above an active region and discuss its consequences in terms of coronal magnetic field modeling. The -plasma model is representative and derived from a collection of sources. The resulting variation with height in the solar atmosphere is used to emphasize that the assumption that the magnetic pressure dominates over the plasma pressure must be carefully employed when extrapolating the magnetic field. This paper points out (1) that the paradigm that the coronal magnetic field can be constructed from a force-free magnetic field must be used in the correct context, since the force-free region is sandwiched between two regions which have >1, (2) that the chromospheric Mgii–Civ magnetic measurements occur near the -minimum, and (3) that, moving from the photosphere upwards, can return to 1 at relatively low coronal heights, e.g., R1.2 R
s. 相似文献
9.
Following our series of works on anisotropic radiation, we analyze the erenkov condition in magnetized plasmas in this paper. We have discovered that the usual erenkov condition cos =1/n isnot satisfied at a far field point in anisotropic media, implying that when a charge is moving in a magnetized plasma, a linear shock wave front does not form. Thus we can calculate the power received at a far field per unit time in such a medium — this quantity could not be evaluated according to previous theory. Numerical examples are presented to show various relevant characteristics of erenkov radiation in model plasmas. 相似文献
10.
Santosh Kumar 《Astrophysics and Space Science》1984,104(1):127-132
For spherical blast waves propagating through a self-gravitating gas with an energy inputE
=E
0
t
, whereE
is the energy released up to timet,E
0 is a functional constant, and is a constant, kinetic, internal heat, and gravitational potential energies have been computed. Taking the parameterA
2, which characterises the gravitational field, equal to 2, variations of the percentages of these energies for =0, 1/2, 4/3, and 3 with shock strength have been presented. For =3, the effect of cavitation on the percentages of kinetic energy and internal heat energies has been explored. 相似文献
11.
PhotoelectricUBV photometry of the long period southern eclipsing binary system W Cru gathered over an 18-mo period in 1984–1985 is presented and examined.The light curve is characterized by continuous Beta Lyrae-like variation: unexpected in such a long period (198.5 days) system; together with peculiar irregularities, of the order of 0.1 mag (or more inU) and time-scales of a few days.A high mass model (total mass 70M
) could be made to be roughly consistent with the data, though alternative models of much lower mass are also possible, and may turn out to be preferable, in terms of goodness-of-fit, as well as for theoretical reasons. The low mass models would require, though, the more massive component to be unseen (as now generally supposed for Lyrae itself).The photometry alone, or even combined with a known spectroscopic mass-function, seems unlikely to be able to furnish a single definitive solution, and more guidelines from reliable theoretical expectation may prove helpful in interpreting the data. 相似文献
12.
The reconnection rate which can be achieved in the steady-state flux-pile-up regime is severely limited by the gas pressure of the plasma. Using the family of solutions obtained previously by Priest and Forbes, we show that the Alfvén Mach number of the plasma flowing towards the reconnection site cannot exceed
e/(8 ln R
me), where
e and R
me are the plasma and magnetic Reynolds numbers at large distance. This limit corresponds to a very weak flux-pile-up, and it is a factor of
e slower than the maximum Petschek rate. Thus the maximum flux-pile-up reconnection rate in the corona is at least two orders of magnitude smaller than the rate implied by flare observations. 相似文献
13.
In the theory of supergravity (N=1), the supersymmetric version of general relativity, and for the Kasner cosmological model (Bianchi type I) we find a non-trivial solution (for the metric and spinor-vector) under the most simple assumption =11 + 22; 12+21=0 and for a special choosed gaugeN=1,N
j=0, 0=0. This method could be also applied to other cosmological metrics and extended to enlarged Grassmann basis.O. Obregón was partially supported by the Alexander von Humboldt Stiftung. 相似文献
14.
Simultaneous observations of chromospheric (H) and photospheric (Fei 5324.19 Å) magnetograms in quiet solar regions enable us to study the spatial configuration of the magnetic field in the solar atmosphere. With the typical spatial resolution of the Huairou magnetograph, the photospheric and chromospheric magnetic structures of the quiet Sun maintain a very similar pattern. Moreover, the vertical magnetic flux is almost the same from the photosphere to the chromosphere. As an intermediate step, we analyze the formation of the working lines used by the Huairou video magnetograph of the Beijing Astronomical Observatory. The Stokes V contribution function of H and Fei 5324.19 Å are calculated. It is found that our H magnetograms provide the distribution of the chromospheric magnetic field at a height some 1000–1500 km above the photosphere. 相似文献
15.
TS. G. Tsvetkov 《Astrophysics and Space Science》1988,150(2):223-234
On the basis of observational data for the absolute R and relative R/R amplitudes of variations in radius of galactic classical cepheids (55 stars from Balona and Stobie (1979) and 30 stars from Sollazzoet al. (1981)), four kinds of empirical linear relations are obtained: log(P V)–logR, logP–logR, log(P V)–log(R/R), and logP–log(R/R);P, R, and V are the pulsation periods, the mean stellar radii, and the amplitudes of light variations, respectively. Three groups of stars are considered: short-period cepheids (SPC)-with logP1.1; long-period cepheids (LPC)-with logP>1.1; and s-cepheids (sC). Both the R values and the R/R values increase withP andP V, for a given group of variables. A comparison is performed with our results obtained from data in other sources (Kurochkin, 1966; Gieren, 1982; etc.). The investigated relations can be applied for determining R and R/R of galactic classical cepheids, by using their observedP and V. All studied galactic classical cepheids have R/R<0.35, R<10R
for SPC and 10R
<R60R
for LPC. The sC have smaller R and R/R values than other classical cepheids, at the same periods (the difference is about 2 times for R and 1.4–2.8 times for R/R); the studied sC have R/R in the range 0.025–0.075 and R in the range 1–3R
(only Y Oph has R8R
). 相似文献
16.
We develop an automatic, computer controlled procedure to select and to analyze the Network Bright Points (NBPs) on solar images. These have been obtained at the Sac Peak Vacuum Tower Telescope by means of the Universal Birefringent Filter and Zeiss H filters, tuned, respectively, along the profiles of the H, Mg-b1, Na-D2, and H lines.A structure is identified as an NBP if at the wavelength H- 1.5 A its maximum intensity is greater than I + 3 and its area is greater than 1.5 arc sec2 at I + 1.5, where I is the mean value and the standard deviation of the intensity distribution on the image. Each detected NBP is then searched and confirmed in all the remaining 31 images at different wavelengths.For each NBP several parameters are measured (position, area, mean and maximum contrast, Dopplergram velocity, compactness, and so on) and some identification constraints are applied.The statistical analysis of the various parameter distributions, for NBPs present within an active region and its surroundings, shows that two types of NBPs can be identified according to the value of their mean contrast C
min the H- 1.5 Å image (C
m 0.1 type I, C
m> 0.1 type II). The type I NBPs (all occurring on the boundaries of the supergranular network) appear to be much more frequent (180/26) than the type II ones.The size A of type I NBPs is less than 1.0 arc sec for H/H wings but of the order of 1.2 arc sec for Na-D2 and Mg-bl. The mean contrast C
m is around the value of 10% along the Na-D2 and Mg-bl profiles and of 20% along the H/H wings.The C
m - A scatter diagrams show, for the photospheric radiation (h < 100 km), a narrow range of variability for C
min correspondence with a wide range for A. For radiation orginated at higher levels (h > 200 km), the C
m- A scatter diagrams seem to indicate, even if with a large variance, that the highest C
m's tend to correspond to the highest A values.The mean Doppler shift is close to zero for Na-D2 and Mg-bl lines but negative (downward motion) for H and H lines.The type II NBPs tends to be preferentially located in the neighbourhood of small, compact sunspots and their detectability is almost constant through all the 4 studied line profiles. No conclusions can be derived on the mean size, contrast and Doppler shift values because their distributions are too dispersed. The only positive information is that its C
m- A scatter diagram, in H and H wings, indicates a wide range of variability for C
m in correspondence with very narrow range of variability for A. 相似文献
17.
The north-south incidence has been studied of 31 white-light flares observed since 1859 and of 1669 events meeting the criteria for major flares of Dodson and Hedeman (1971) for the period 1955–1974. The asymmetry in favor of the northern hemisphere increases strikingly with the importance of the events. Similarly, magnetically complex sunspot groups (Mt. Wilson classes, and) display a more pronounced asymmetry in favor of the north than non-complex groups for 1962–1970. Contrary to the flare asymmetry, the spottedness asymmetry is independent of the size of sunspots. 相似文献
18.
Hong-Nan Zhou 《Astrophysics and Space Science》1988,141(2):199-206
The contact binary system CC Com (=12h09m33s.8, =+22°4339, (1950);V
max=11.31, (B-V)max=1.24) is a W UMa-type system with the shortest known period. The photometric solution of CC Com is presented using the Wilson and Devinney method. The results show that the CC Com belongs to the late-type eclipsing binary with the spectral type K5V and K6V, low temperatureT
1=4300 K,T
2=4265 K, the mass ratioq=0.5873±0.0021, and the inclinationi=87°.719±1°.44. The best regions of the gravity darkening exponents , the bolomotric albedov, and the limb-darkening coefficients are tested. It is found that 0.1250.065, 0.1v0.5, =0.5 are better regions for CC Com. The third body ofl
3 is not found to be significant. The results are combined with the spectroscopic results of Rucinski to provide an estimate of the absolute parameters. 相似文献
19.
For a cylindrical wave guide, filled with hot collisional and moving plasma, the expression for damping coefficientK
i (imaginary part of the wave vector) has been derived and discussed in case of TM modes. It is observed that due to the effects of ion collisions,K
i remains less than zero for all values of (=/c) and waves suffer strong reflections for 0.5. The damping is however not affected for moderate changes in collision frequencies, while for low values of electron collision frequency and plasma density, the damping coefficient varies in a parabolic fashion with sharp reflections at 0.3. 相似文献
20.
A detailed study of classical polytropes in general relativity has been presented for O ((dP/dE)O) 1.0 and O((P/E
O)O. The behaviour of various structural parameters with O/O, O and O are the values ofP/E and dP/dE at the centre) has been studied. The most important result of this study is the fact the qualitative behaviour of all the structural parameters depends only on the value of µO for the various assigned O values. The maximum value of surface red shift occurs when µO=0.6 and for O=1.0 it equals 0.618. These structures are gravitationally bound for µO0.8 and most so for µO=0.4. The maximum value of binding coefficient comes out to be 0.181 when O=1.0. These structures have been used to model neutron stars. The maximum mass of neutron star based upon such a model comes out to be 2.55M
(for µO=0.4 and O=1.0) and maximum size comes out to be 15.0 km (for µO=0.2 and O=1.0). It is also seen that the structures are pulsationally stable for µ0.6. 相似文献