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1.
B. Schmieder 《Solar physics》1977,54(2):269-288
A method coupling the hydrodynamical equations and radiative transfer in a realistic solar model atmosphere is described. The influence of the temperature gradient of the model and the radiative dissipation is pointed out.The effect of the large temperature gradient is important in the layers where the optical depth 5000 is greater than 0.5; the ratio between the amplitude of the temperature and the velocity fluctuations decreases with the altitude by a factor 2 between = 1 and = 0.5 and in the case of the acoustic waves, the phase shift between these fluctuations is small.The radiative energy loss in the thick layers (
5000 = 1) leads to a decrease of the vertical phase velocity of the waves and to a damping of their amplitudes in the layers of intermediate optical depth (10-2 < 5000 < 0.5). The effect of the dissipation is negligible in the thin layers (5000 < 10-2). 相似文献
2.
Absolute wavelengths for Fraunhofer lines are compared with laboratory measurements for several atomic and molecular spectra. The wavelength differences are shown to be consistent with the proposal that the deeper layers of the photosphere are in convective motion:
e
-3 km/sec for log 0> -1.0. Convective motions in the outer layers (log0< - 1.0) are shown to be very small. Wavelength shifts of Fraunhofer lines formed in these outer layers are in good quantitative agreement with the predictions of the General Theory of Relativity. 相似文献
3.
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
4.
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
5.
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
6.
Observations of the lines He i 3888 and H8 in 80 quiescent prominences by the author, and in other prominences by Kubota et al. (1972) and Morozhenko (1971), have been used to derive the dependences of I(3888)/I(H8) on I(H8), N
2
3
s
on 0 (H), and N
+
n
e
on 0(H) (Figures 1, 2, 3 and 4). The equations of ionization equilibrium and triplet system steady state for a helium atom (27 levels and continuum were considered) were solved together with the radiation transfer equation in the helium Lyman continuum. As given n
e
() distribution with depth and T
e
=7500 K were assumed. The 23
S level population N2
3
s, helium emission measure N
+
n
e
and the intensity ratios of the He i 3888 and H8 lines were calculated and compared with observation (Figures 2, 3 and 4, solid lines). The figures show that in bright prominences the observed values of N
2
3
s and N
+
n
e
are systematically higher than the calculated ones. These deviations cannot be eliminated by decreasing n
e
. One can make the calculations and observations agree for bright prominences by increasing the UV radiation which penetrates into the prominence. 相似文献
7.
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
8.
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
9.
Leaky tube waves are examined in the context of kink oscillations in coronal loops, observed in recent years using TRACE. It is pointed out that the standard (non-leaky) principal kink mode has a leaky bifurcated counterpart with decay time 4–4(L/R)2
P, where R and L are the loop radius and length, and P is the oscillation period. This is somewhat too long to explain the observed decays, except for very short or thick loops, but may be implicated in the initial excitation. Higher harmonics decay much more rapidly. The external solution takes the form of a wave running nearly parallel to the tube, but with a small outward component. In addition, a number of other leaky modes are described which decay on timescales of seconds, =Ra
e/a
2, where a and a
e are the loop and external Alfvén speeds respectively, and which can be identified as being almost radially propagating fast magnetoacoustic waves. These are outside the currently observable range, but are likely to be important energetically. 相似文献
10.
M. Šidlichovský 《Celestial Mechanics and Dynamical Astronomy》1980,22(4):343-355
The first-order perturbations of a system of two triaxial rigid spheroids under Hori-Lie transformation are investigated. The time dependence of the configuration of the three angular momentum vectors, two rotational and one orbital, is studied. The problem is simplified by the introduction of a new time parameter , such thatt is the hyperelliptic function of . The projectionsH
1 andH
2 of the rotational momentum vectors into the direction of the total angular momentum vector of the system are then harmonic or exponential functions of . The trajectory in theH
1,H
2 plane is a part of an ellipse or hyperbola respectively. If this conical section intersects a certain critical contourC, the system is bounced back along the original trajectory. The motion of the relative configuration of the angular momentum vectors is periodical except in a special aperiodic case. The expressions for the periods are given. 相似文献
11.
Using the see-saw mechanism and estimation of the hypothetical mass of the electron neutrinom
e we find the hypothetical mass of muon neutrinom
µ and hypothetical mass of the tau neutrinom
. 相似文献
12.
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
13.
T. D. Padalia 《Astrophysics and Space Science》1993,202(1):63-68
Forty-six binary systems with their primary component masses between 2M
and 3M
have been considered for gravitational radiation study. Power output by gravitational radiation (P
B
) and spiral time
0 for all individual systems have been evaluated. A relation has been given betweenP
B
and
0. The rate of decrease of orbital period (P) has also been given for 10 eccentric orbit systems. 相似文献
14.
With the help of a model atmosphere of the Sun we evaluate the pole-equator difference in flux (as measured by Dicke and Goldenberg) assuming the following type of pole-equator temperature difference (T=T
e
–T
p
): (a) T 2K for > 0 (0 0.05); (b) T 10K for < 0.The small T at all optical depths given by (a) could, for example, be due to a pole-equator difference in effective temperatures. At small optical depths a difference in mechanical heating could give rise to the larger temperature difference given by (b). We compare the results of our calculations with Dicke and Goldenberg's observations.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
15.
J. Perdang 《Astrophysics and Space Science》1982,83(1-2):311-333
We show that the overall densityg() of asymptotic acoustic frequencies of a star obeys a Weyl lawg()
D–1, whereD is the dimensionality of the oscillating stellar configuration. For realistic stars with a finite non-zero surface sound speed,D is equal to the actual dimensionality of the star,D=3. For formal models with a vanishing sound velocity at the surface, heuristic arguments lead to a dimensionality parameterD=4.5. The empirical frequencies of Eddington's standard model are found to be consistent with the latter distribution, with reasonable agreement already occurring in the low-frequency range >
i
2× fundamental radial mode. We argue that real stars obey this 3.5-power law in some finite frequency interval
i
<<
f
,
f
being a very high frequency critically depending on the surface sound velocity, while the full asymptotic law, withD=3, holds for >
f
. 相似文献
16.
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
17.
Dlugach Zh. M. Korablev O. I. Morozhenko A. V. Moroz V. I. Petrova E. V. Rodin A. V. 《Solar System Research》2003,37(1):1-19
Atmospheric aerosols play an important role in forming the Martian climate. However, the basic physical properties of the Martian aerosols are still poorly known; there are many contradictions in their estimates. We present an analytical overview of the published results and potentialities of various methods. We consider mineral dust. Zonally averaged data obtained from mapping IR instruments (TES and IRTM) give the optical thickness of mineral aerosols 9 = 0.05–0.1 in the 9-m band for quite atmospheric conditions. There is a problem of comparing these estimates with those obtained in the visible spectral range. We suggest that the commonly used ratio vis/9 >2 depends on the interpretation and it may actually be smaller. The ratio vis/9 1 is in better agreement with the IRIS data (materials like montmorillonite). If we assume that vis/9 = 1 and take into account the nonspherical particle shape, then the interpretation of ground-based integrated polarimetric observations ( < 0.04) can be reconciled with IR measurements from the orbit. However, for thin layers, the sensitivity of both methods to the optical thickness is poorly understood: on the one hand, polarimetry depends on the cloud cover and, on the other hand, the interpretation of IR measurements requires that the atmospheric temperature profile and the surface temperature and emissivity be precisely known. For quite atmospheric conditions, the local optical-thickness estimates obtained by the Bouguer–Lambert–Beer method and from the sky brightness measured from Viking 1 and 2 and Mars Pathfinder landers are much larger: = 0.3–0.6. Estimates of the contrasts in images from theVikingorbiters yield the same values. Thus, there is still a factor of 3 to 10 difference between different groups of optical-thickness estimates for the quiet atmosphere. This difference is probably explained by the contribution of condensation clouds and/or by local/time variations. 相似文献
18.
The problem to compute the magnetic field above the chromosphere using data of the vector = B
t/Bt that gives the projected field direction can be solved with different approximations. The field of direction vectors is, however, not the only field accessible to observations. The Stokes parameters, which are components of the radiation tensor, can be measured at each point of the image plane. The directions of the eigenvectors of the radiation tensor define two mutually orthogonal systems of integral curves in the image plane. These families of curves have singular points, which are generally of different type than those of the vector field. When the morphology of H chromospheric fibrils are used to infer the topology of the magnetic field, a similar problem is met, suggesting that singular points should also be present there. 相似文献
19.
J. Baumgarte 《Celestial Mechanics and Dynamical Astronomy》1976,14(1):121-127
The paper introduces a new time element to be used with a general time transformation for satellite equations of motion. The purpose of this time element is to reduce the growth of the numerical errors with respect to the time integration. It is characteristic for the new time element , that the relation between the timet and the element does not depend on the independent variables. 相似文献
20.
Multi-cloud model (MCM) method and its applications to the study on asymmetric spectral profiles 总被引：1，自引：0，他引：1
A method of multi-cloud model (MCM) is proposed in this paper in order to research asymmetric profiles of spectral line formed by solar discrete active objects aligned along the line-of-sight difection. Based on the MCM method, under the conditions of certain assumptions and approximations, the line-of-sight velocityV and three other physical parameter approximation values, (i.e. Doppler width
D
, source functionS and optical depth at line center 0) within different clouds may be derived simultaneously by fitting both profiles theoretical and observational. An application example of the method withm=3 shows that MCM method is suitable to measure the velocity fields of multi-object at the same time from their non-Gaussian profiles of complex. TheV and
D
derived from the method are reliable,S and 0 are approximation. An influence of the variations of initial values in the parameter on the solution is given as well. 相似文献