共查询到20条相似文献，搜索用时 250 毫秒
1.
В. М. Чаругин 《Astrophysics and Space Science》1975,37(2):441-447
, . N/E, E
r, (E
r)=1. , (, ) . . 相似文献
2.
A fraunhofer line profile depends on various parameters, partly related to the photospheric structure (T, P
g, P
e, v
conv, v
turb), partly to the atom or ion involved (such as oscillator strength, energy levels), partly also resulting from the interaction of the relevant kind of particles with the photosphere, and the photospheric radiation field. In this paper we shall mainly pay attention to the determination of: the macroturbulent (convective) velocities, v
conv (); the damping constant (); the abundance, A
el; the distribution function (v
conv, ) of the convective velocities at each depth ; the source function, S (); the microturbulent velocities, v
turb ().The particular difficulty with these unknowns is that they are, as a rule, coupled in the resulting line profiles, that is: the shapes and intensities in these profiles are determined by the combined influence of these unknowns (together with the other above-given parameters).In this paper we describe a method to determine these six unknowns empirically by separating them, in analysing accurate high-resolution observations of line profiles of a multiplet. The unknown functions and quantities are consecutively determined in the above given succession. For each determination another, appropriate part of the line profile is used. In some cases the influence of the mutual coupling of the various parameters cannot be completely eliminated, and an iterative method has to be used.The method is summarized in Table II and section 2, and is further explained in sections 3 to 8. It is applied to an infrared Ci multiplet. The main results are the following: 相似文献
3.
The accuracy of the approximate replacement of the frequency meanj() of the total intensityJ
() byJ
c+a{J
0()–J
c} by Geovenelli, whereJ
c is the total intensity at the continuum,J
0() is that at the line center anda is independent of depth, is studied. Numerical calculations for strong solar lines show very high values of the residual intensities. A slight change in the approximation is then suggested to get a result quite consistent with observational and existing calculated data. 相似文献
4.
5.
W. -H. Ip 《Astrophysics and Space Science》1974,31(1):57-79
The problem of planetary accretion in a jet stream is studied using the model developed by Alfvén and Arrhenius. We find that there are basically three types of planetary accretion: namely, fast process
c
<
i
, slow process
c
~
i
and delayed process
c
>
i
where
c
is the characteristic time of the occurrence of catastrophic accretion and
i
the time-scale of mass injection to the planetary system (3×108 yr). These different time scales of accretion are found to be closely related to the primordial thermal profiles and equatorial inclinations of the planets. Finally, Venus' retrograde rotational spin is shown to be a possible result of accretion process in a jet stream. 相似文献
6.
S. T. Revankar 《Astrophysics and Space Science》1982,86(1):13-23
Free convection effects on MHD flow past a semi infinite porous flat plate is studied when the time dependent suction velocity changes in step function form. The solution of the problem is obtained in closed form for the fluid with unit Prandtl number. It is observed that for both cooling and heating of the plate the suction velocity enhances the velocity field. The heat transfer is higher with increase in suction velocity.Notations
B
intensity of magnetic field
-
G
Grashof number
-
H
magnetic field parameter,H=(M+1/4)
1/2–1/2
-
M
magnetic field parameter
-
N
u
Nusselt number
-
P
Prandtl number of the fluid
-
r
suction parameter
-
T
temperature of the fluid
-
T
w
temperature of the plate
-
T
temperature of the fluid at infinity
-
t
time
-
t
non-dimensional time
-
u
velocity of the fluid parallel to the plate
-
u
non-dimensional velocity
-
U
velocity of the free stream
-
suction velocity
- 1
suction velocity att0
- 2
suction velocity att>0
-
x,y
coordinate axes parallel and normal to the plate, respectively
-
y
non-dimensional distance normal to the plate
-
coefficient of volume expansion
-
thermal diffusivity
-
kinematic viscosity
-
electric conductivity of the fluid
-
density of the fluid
-
non-dimensional temperature of the fluid
-
shear stress at the plate
-
non dimensional shear stress
- erf
error function
- erfc
complementary error function 相似文献
7.
I. W. Roxburgh 《Solar physics》1972,27(2):478-480
Three different asymptotic branches of the two-fluid equations are found with
e
m
,
p
n
, where, is the inverse distance from the Sun, with (m, n) = (2/7, 2/7), (2/7, 6/7), (4/3, 4/3); other special solutions are also found but they correspond to special choices of density and temperature at the corona. In all the (4/3, 4/3) solutions, the electron and proton temperatures tend to equality at large distances.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
8.
A novel methodology for evaluating the field of anisotropically scattered radiation within a homogeneous slab atmosphere of arbitrary optical thickness is provided. It departs from the traditional radiative transfer approach in first considering that the atmosphere is illuminated by an isotropic light source. From the solution of this problem, it subsequently proceeds to that for the more conventional case of monodirectional illumination. The azimuthal dependence of the field is separated in the usual manner by an harmonic expansion, leaving a problem in four dimensions (=optical depth, 0=thickness, , =directions of incidence and scattering) which, as is well known, is numerically extremely inconvenient. Two auxiliary radiative transfer formulations of increasing dimensionality are considered: (i) a transfer equation for the newly introduced functionb
m(,,0) with Sobolev's function
m(,0) playing the role of a source-function. Because the incident direction does not intervene,
m is simply expressed as a single integral term involvingb
m. For bottom illumination, an analogous equation holds for the other new functionh
m(,,0). However, simple reciprocity relations link the two functions so that it is only necessary to considerb
m; (ii) a transfer equation for the other new functiona
m(,,,0) with a source-function provided by Sobolev's functionD
m(,,0). For bottom illumination, another functionf
m(,,,0) is introduced; by a similar argument using reciprocity relations,f
m is reduced toa
m rendering necessary only the consideration ofa
m. However, a fundamental decomposition formula is obtained which shows thata
m is expressible algebraically in terms of functions of a single angular variable. The functions
m andD
m are shown to be the values in the horizontal plane ofb
m anda
m, respectively. The other auxiliary functionsX
m andY
m are also expressed algebraically in terms ofb
m. These results enable one to proceed to the final step of evaluating the radiation field for monodirectional illumination. The above reductions toalgebraic relations involving only the functionb
m appear to be more advantageous than Sobolev's (1972) recent approach; they also circumvent some basic numerical difficulties in it. We believe the present approach may likewise prove to be superior to most (if not all) other methods of solution known heretofore.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory under Contract No. NAS-7-100 sponsored by the National Aeronautics and Space Administration. 相似文献
9.
P. G. Kazantzis 《Astrophysics and Space Science》1980,69(2):353-368
New families of three-dimensional double-symmetric periodic orbits are determined numerically in the Sun-Jupiter case of the restricted three-body problem. These families bifurcate from the vertical-critical orbits (
v
= – 1, b
v
– 0) of the basic plane familiesi, g
1, g2, c andI. Further, the predictor-corrector procedure employed to reveal these families has been described and interesting numerical results have been pointed out. Also, computer plots of the orbits of these families have been shown in conical projections. 相似文献
10.
The optical depth at the head of the Lyman continuum,
H, is determined at a number of positions in three hedgerow prominences using spectroheliograms (5 × 5 resolution) of C III 977, LC 896, and O IV 554 observed with the Harvard experiment on Skylab. At heights greater than 10 above the limb the maximum value of
H is 30 to 50, which occurs at the central part of the prominences. For one of the prominences the determination of
H is found to be consistent with data from spectroheliograms of Mg X 625. The degree of ionization of hydrogen is estimated from the intensity of LC 896 at
H 1. In the central part of a model prominence N
P/N
HI1.9 for a reasonable range of the electron densities, where N
P and N
HI are the proton density and the neutral hydrogen density, respectively. 相似文献
11.
The observation of [OI] 6300 » emission in the coma of Halley's comet 1982i, using the imaging Fabry-Pérot spectrometer, was carried out from Gurushikhar (2439N, 7243E, 1700m altitude), Mt. Abu, India on March 15, 1986 (R = 0.90 AU, = 0.96 AU). The analysis of the interferogram show the absence of the differential velocity of neutral oxygen above 5 km s–1. 相似文献
12.
RecentUBV photometry of the RS CVn binary CF Tuc is discussed and analysed. If we combine the results with previously published spectroscopy we find radii of 1.63R
for the hotter (6000 K) and 3.11R
for the cooler (4500 K) component; both stars having a mass of about 1.3M
. The distance to the system is put at 86±15 pc.Though the photometric data is incomplete in the coverage of some regions out of the minima, there is no significant evidence of the wave-type distortions — a known hallmark of RS CVn stars — and the data can be modeled by a standard eclipsing binary system in which the statistical test of goodness-of-fit (2) produces quite acceptable values for reasonable estimates of observational accuracy (0.01 mag). We, therefore, have no need to postulate any additional photometric complications, and feel entitled to some confidence in the reliability of the derived parameter set. 相似文献
13.
Mohamed Adelsharaf 《Astrophysics and Space Science》1979,60(1):199-212
In this paper, a technique of recursive analysis is developed for the integral transform A of the exponential integral functionsE
n which is denoted as
n
(). The main result of this analysis enables us to establish a two-term recurrence formula for
n
(0) and a three-term recurrence formula for
n
(); 0. A computational algorithm based on these formulae is also constructed and its numerical results forn=2(1)25 are presented to 15-digit accuracy. 相似文献
14.
A. A. Stepanian B. M. Vladimirsky Yu. I. Neshpor V. P. Fomin 《Astrophysics and Space Science》1975,38(2):267-282
The results of the observations to search gamma-ray sources with the energy greater than 2×1012 eV, which were made in Crimean Astrophysical Observatory during the years 1969–73 are presented. A technique of the detection of the EAS Cerenkov flashes was used.The quality of the data obtained is analysed. The criteria for the selection of the data free from meteorological variations are considered.It was shown that two objects, namely, Cyg X-3 and Cas -1, may be the sources of high-energy gamma quanta. It is probable that the object with the coordinates =05h15m, =+1° is the source of gamma-rays as well. An unidentified object Cas -1 is variable: gamma-ray flux was observed twice — in Sepember–October 1971 and in December 1972. It is possible that the flux from Cyg X-3 has a period of 4.8 hr.
I I , I I , - >2.1012 . I . I , I I, I ., - -1 Cyg -3- -I . , =0515 ·=+1° -.I -1 I: I J I- - 1971 1972 . Cyg -3, , - T=4.8 .相似文献
15.
A family of symplectic integrators adapted for the integration of perturbed Hamiltonian systems of the form H=A+B was given in (McLachlan, 1995). We give here a constructive proof that for all integer p, such integrator exists, with only positive steps, and with a remainder of order O(p + 22), where is the stepsize of the integrator. Moreover, we compute the analytical expressions of the leading terms of the remainders at all orders. We show also that for a large class of systems, a corrector step can be performed such that the remainder becomes O(p +42). The performances of these integrators are compared for the simple pendulum and the planetary three-body problem of Sun–Jupiter–Saturn. 相似文献
16.
A model of a first generation intermediate star of 5M
, with Z=0 has been considered. The model is at an advanced stage of its evolution and has a double shell burning. It burns helium in the inner shell, and hydrogen, via CNO cycle, in the outer shell.
=(log/log)
T
and
T
=(log/logT)
were computed allowing for the oscillations of the relative mass abundance of the reagents in nuclear reactions. Including
=(log/log)
T
and
=(log/logT)
of mean molecular weight and the effect of the oscillations of abundances due to nuclear reactions, stability was studied. Contrary to the results of the static calculations, we found that instability due to the excitation mechanism provided by the high temperature sensitivity of energy generation rate propagates up to the surface. Thus the model in question was found to be unstable against radial adiabatic pulsations, in its fundamental mode. 相似文献
17.
Free convection in a conducting liquid past an infinite porous vertical flat plate in a rotating frame of reference when the Hall current is present is considered. Exact solutions for the velocity and temperature fields have been derived. The effects ofM (Hartmann number),m (Hall parameter), andE (Ekman number) on the velocity field are discussed.Nomenclature
C
p
specific heat at constant pressure
-
g
acceleration due to gravity
-
E
Ekman number
-
G
Grashof number
-
H
0
applied magnetic field
-
j
x
,j
y
,j
z
components of the current densityJ
-
k
thermal conductivity
-
M
Hartmann number
-
m
Hall parameter
-
P
Prandtl number
-
Q
heat flux per unit area
-
T
temperature of the fluid near the plate
-
T
w
temperature of the plate
-
T
temperature of the fluid in the free-stream
-
u, v, w
components of the velocity fieldq
-
U
uniform free-stream velocity
-
w
0
suction velocity
-
x, y, z
Cartesian coordinates
-
z
dimensionless coordinate normal to the plate
Greek symbols
coefficient of volume expansion
-
e
cyclotron frequency
-
e
electron collision time
-
u
skin friction in the direction ofu
-
v
skin friction in the direction ofv
-
dimensionless temperature
-
density of the fluid
-
kinematic viscosity
-
e
magnetic permeability
-
electrical conductivity of the fluid
-
angular velocity 相似文献
18.
19.
I. Malakpur 《Astrophysics and Space Science》1977,47(1):17-24
The aim of this paper has been to study the neutral helium triplet emission lines identified in the spectrum of the envelope of Nova Delphini. By comparing the observed flux of the neutral helium lines with that calculated theoretically by Robbins, we find that the optical thickness in the center of the line 3889 is of the order of 21.50 for summer 1969. The optical thickness obtained by this method is here denoted tran(3889).On the other hand, we obtain the number of neutral helium atoms in the 23S state [N(23S)] by considering the equilibrium between the mechanisms that populate and depopulate this state. We then find that the depopulation by photoionization due to the radiation of Ly (Hi), transitions to the 21S, 21p and 23p states by electron collision, photoionization due to the continuum radiation of the central star, are 82.70%, 13.20%, 2.40%, 0.90% and 0.80% respectively. We find that the mechanism of the photoionization by Ly is the dominant mechanism of depopulation of 23S state. We calculated ( 3889) of the order of 82.37, fromN(23S), obtained in the preceding paragraph. The optical thickness obtained by this method is here denoted bal(3889).The difference between tran(3889) and bal(3889) is very large and it cannot be attributed to calculation errors. We have considered all the mechanisms that can depopulate the 23S state, so we then conclude that the difference between tran(3889) and bal(3889) is due to the heterogeneity of the envelope of the Nova, already found by us in our previous study of the profiles of the permitted and forbidden lines. Finally, we find from this study a filling factor of the order of 0.30. 相似文献
20.
, . : , . , . . ( ) . . . HZ Her=Her X1, . . , . , ., hv 15–30 . , . Sco X1 . 相似文献