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1.
The ratios I(K
1)/I(H
1) and I(K
3)/I(H
3) were calculated from four semi-empirical models of sunspot umbra. We determined the dependencies of both ratios of such parameters as temperature gradient and atmospheric opacity. A certain influence on the expected ratios I(K
1)/I(H
1) and I(K
3)/I(H
3) can also come from the FIP effect provided it exists in the chromosphere above sunspot umbra. Theoretical and observed values of I(K
1)/I(H
1) and I(K
3)/I(H
3) are compared. It is shown that for one of the sunspots we observed, the values obtained for the ratio I(K
1)/I(H
1) cannot be explained in terms of existing umbra models. 相似文献
2.
The electron collision excitation rates recently calculated for transitions in Si xiii by Keenan et al. (1987) are used to derive the electron temperature sensitive ratio G(=(f + i)/r and the density sensitive ratio R(=f/i), where i, f, and r are the intercombination (1s
2
1
S – 1s2p
3
P
1, 2) forbidden (1s
2
1
S – 1s2s
3
S), and resonance (1s
2
1
S – 1s2p
1
P), transitions respectively. Also estimated are the values of R in the low-density limit (R
0) as a function of electron temperature. The theoretical G ratio at the temperature of maximum emissivity for Si xiii, G(T
m) = 0.70, is in much better agreement with the observed G for the 1985, May 5 flare determined by McKenzie et al. (G = 0.60 ± 0.07) than is the earlier calculation of Pradhan, who derived G(T
m) = 0.85. The error in the observed R
0 ratio is so large that both our result and Pradhan's fall within the acceptable limits of uncertainty and hence one cannot estimate which of the two is the more accurate. 相似文献
3.
The recent twelve-state R-matrix calculations of electron excitation rates in Ciii by Berrington are used to derive level populations applicable to the solar transition region. Line ratios R = I(2p
2 3
P
e
- 2s2p
3
P
°)/I(2s2p
1
P
° - 2s
2 1
S
e
) and R
2=I(2p
2 1
S
e
- 2s2p
1
P
°)/I(2p
2 3
P
e
- 2s2p
3
P
°) deduced from these data in conjunction with the relevent transition probabilities are found to be in much better agreement with the observed quiet Sun values than those determined from the level population calculations of Keenan et al. 相似文献
4.
G. V. Abrahamyan 《Astrophysics》2003,46(3):304-318
New methods are applied to samples of classical cepheids in the galaxy, the Large Magellanic Cloud, and the Small Magellanic Cloud to determine the interstellar extinction law for the classical cepheids, R
B:R
V:R
I:R
J:R
H:R
K= 4.190:3.190:1.884:0.851:0.501:0.303, the color excesses for classical cepheids in the galaxy, E(B-V)=-0.382-0.168logP+0.766(V-I), and the color excesses for classical cepheids in the LMC and SMC, E(B-V)=-0.374-0.166logP+0.766(V-I). The dependence of the intrinsic color (B-V)0 on the metallicity of classical cepheids is discussed. The intrinsic color (V-I)0 is found to be absolutely independent of the metallicity of classical cepheids. A high precision formula is obtained for calculating the intrinsic colors of classical cepheids in the galaxy: (<B>-<V>)0=0.365(±0.011)+0.328(±0.012)logP. 相似文献
5.
Constantino Tsallis 《Astrophysics and Space Science》2006,305(3):261-271
The cornerstones of Boltzmann-Gibbs and nonextensive statistical mechanics respectively are the entropies S
BG
≡ −k ∑
i = 1
W
p
i
ln p
i
and S
q
≡ k (1−∑
i = 1
W
p
i
q
)/(q−1) (q∊ℜ S
1 = S
BG
). Through them we revisit the concept of additivity, and illustrate the (not always clearly perceived) fact that (thermodynamical) extensivity has a well defined sense only if we specify the composition law that is being assumed for the subsystems (say A and B). If the composition law is not explicitly indicated, it is tacitly assumed that A and B are statistically independent. In this case, it immediately follows that S
BG
(A+B) = S
BG
(A)+S
BG
(B), hence extensive, whereas S
q
(A+B)/k = [S
q
(A)/k]+[S
q
(B)/k]+(1−q)[S
q
(A)/k][S
q
(B)/k], hence nonextensive for q ≠ 1. In the present paper we illustrate the remarkable changes that occur when A and B are specially correlated. Indeed, we show that, in such case, S
q
(A+B) = S
q
(A)+S
q
(B) for the appropriate value of q (hence extensive), whereas S
BG
(A+B) ≠ S
BG
(A)+S
BG
(B) (hence nonextensive). We believe that these facts substantially improve the understanding of the mathematical need and physical origin of nonextensive statistical mechanics, and its interpretation in terms of effective occupation of the W
a priori available microstates of the full phase space. In particular, we can appreciate the origin of the following important fact. In order to have entropic extensivity (i.e., lim
N→∞
S(N)/N < ∞, where N≡ numberof
elements
of
the
system), we must use (i) S
BG
, if the number W
eff of effectively occupied microstates increases with N like W
{{eff}}∼ W ∼ μ
N
(μ ≥ 1); (ii) S
q
with q = 1−1/ρ, if W
{{eff}}∼ N^ρ < W (ρ ≥ 0). We had previously conjectured the existence of these two markedly different classes. The contribution of the present paper is to illustrate, for the first time as far as we can tell, the derivation of these facts directly from the set of probabilities of the W microstates. 相似文献
6.
Theoretical electron-density-sensitive C III emission line ratios are presented forR
1 =I(2s2p
3
P – 2p
2
3
P)/I(2s2p
1
P – 2p
2
1
S) =I(1176 Å)/I(1247 Å),R
2 =I(2s2p
3
P – 2p
2
3
P)/I(2s
2
1
S – 2s2p
3
P
1) =I(1176 Å)/I(1908 Å), andR
3 =I(2s2p
1
P – 2p
2
1
S)/I(2s
2
1
S – 2s2p
3
P
1) =I(1247 Å)/I(1908 Å). These are significantly different from those deduced previously, principally due to the adoption of improved electron impact excitation rates in the present analysis. Electron densities deduced from the present theoretical line ratios, in conjunction with observed values ofR
1,R
2, andR
3 measured from solar spectra obtained by the Naval Research Laboratory's S082B instrument on boardSkylab, are found to be generally compatible. In contrast, previous diagnostic calculations imply electron densities fromR
1,R
2, andR
3 that differ by up to two orders of magnitude. These results provide observational support for the accuracy of the atomic physics adopted in the present calculations, and the methods employed in the derivation of the theoretical line ratios. 相似文献
7.
We present new laboratory data on the multiplets 2s
2
1
S -2s2p
3
P, 2s
22p
2
P - 2s2p
2
4
P, and 2s
22p
2
3
P - 2s2p
3
5
S in nitrogen, oxygen and fluorine, and discuss theZ-dependence of their wave-numbers. These multiplets are very faint in laboratory light sources, but can become prominent in
astrophysical sources of low density. Our results confirm the solar identifications of the nitrogen and oxygen multiplets
made by Burtonet al. Predicted positions of the corresponding multiplets in neon are given. 相似文献
8.
S. Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》1994,58(4):387-391
This paper considers the integrability of generalized Yang-Mills system with the HamiltonianH
a
(p, q)=1/2(p
1
2
+p
2
2
+a
1
q
1
2
+a
2
q
2
2
)+1/4q
1
4
+1/4a
3
q
2
4
+ 1/2a
4
q
1
2
q
2
2
. We prove that the system is integrable for the cases: (A)a
1=a
2,a
3=a
4=1; (b)a
1=a
2,a
3=1,a
4=3; (C)a
1=a
2/4,a
3=16,a
4=6. Our main result is the presentation of these integrals. Only for cases A and B does the Yang-Mills Hamiltonian possess the Painlevé property. Therefore the Painlevé test does not take account of the integrability for the case C. 相似文献
9.
10.
F. Zagury 《Astronomische Nachrichten》2012,333(2):160-165
This article discusses the interstellar extinction curve in the visible and the value of the ratio of absolute to selective extinction RV = AV/E (B – V). It is concluded that the visible extinction curve is likely to be linear in the visible and that indirect estimates of RV from tentative determinations of AV or from infrared and UV observations are questionable. There is currently no evidence of any variation of RV with direction. If RV is close to 3, as it has been inferred from mid‐infrared data, starlight in the visible is extinguished by a factor F /F0 = (2.5 e–2μm/λ)E (B –V). But if the visible wavelength range alone is considered, 4 appears as its most natural and probable value and F /F0 = e–2E (B –V)/λ (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
We study the stability of motion in the 3-body Sitnikov problem, with the two equal mass primaries (m
1 = m
2 = 0.5) rotating in the x, y plane and vary the mass of the third particle, 0 ≤ m
3 < 10−3, placed initially on the z-axis. We begin by finding for the restricted problem (with m
3 = 0) an apparently infinite sequence of stability intervals on the z-axis, whose width grows and tends to a fixed non-zero value, as we move away from z = 0. We then estimate the extent of “islands” of bounded motion in x, y, z space about these intervals and show that it also increases as |z| grows. Turning to the so-called extended Sitnikov problem, where the third particle moves only along the z-axis, we find that, as m
3 increases, the domain of allowed motion grows significantly and chaotic regions in phase space appear through a series of
saddle-node bifurcations. Finally, we concentrate on the general 3-body problem and demonstrate that, for very small masses, m
3 ≈ 10−6, the “islands” of bounded motion about the z-axis stability intervals are larger than the ones for m
3 = 0. Furthermore, as m
3 increases, it is the regions of bounded motion closest to z = 0 that disappear first, while the ones further away “disperse” at larger m
3 values, thus providing further evidence of an increasing stability of the motion away from the plane of the two primaries,
as observed in the m
3 = 0 case. 相似文献
12.
A rigorous theoretical investigation of nonlinear electron-acoustic (EA) waves in a plasma system (containing cold electrons, hot electrons obeying a Boltzmann distribution, and hot ions obeying a nonthermal distribution) is studied by the reductive perturbation method. The modified Gardner (MG) equation is derived and numerically solved. It has been found that the basic characteristics of the EA Gardner solitons (GSs), which are shown to exist for α around its critical value α c [where α is the nonthermal parameter, α c is the value of α corresponding to the vanishing of the nonlinear coefficient of the Korteweg-de Vries (K-dV) equation, e.g. α c ≃0.31 for μ=n h0/n i0=0.5, σ=T h /T i =10, n h0, n i0 are, respectively, hot electron and nonthermal ion number densities at equilibrium, T h (T i ) is the hot electron (ion) temperature], are different from those of the K-dV solitons, which do not exist for α around α c , and mixed K-dV solitons, which are valid around α∼α c , but do not have any corresponding double layers (DLs) solution. The parametric regimes for the existence of the DLs, which are found to be associated with positive potential, are obtained. The present investigations can be observed in various space plasma environments (viz. the geomagnetic tail, the auroral regions, the cusp of the terrestrial magnetosphere, etc.). 相似文献
13.
Rafael Cid María-Eugenia San Saturio 《Celestial Mechanics and Dynamical Astronomy》1987,42(1-4):263-277
In this article we study the conditions for obtaining canonical transformationsy=f(x) of the phase space, wherey(y
1,y
2,...,y
2n
) andx(x
1,x
2,...,x
2m
) in such a way that the number of variables is increased. In particular, this study is applied to the rotational motion in functions of the Eulerian parameters (q
0,q
1,q
2,q
3) and their conjugate momenta (Q
0,Q
1,Q
2,Q
3) or in functions of complex variables (z
1,z
2,z
3,z
4) and their conjugate momenta (Z
1,Z
2,Z
3,Z
4) defined by means of the previous variables. Finally, our article include some properties on the rotational motion of a rigid body moving about a fixed point. 相似文献
14.
A comparison of Skylab S082A observations for several solar flares with calculations of the electron temperature sensitive emission line ratio R
1 = I(2s2p
1
P – 2s
2
1
S)/I(2s2p
3
P
1 - 2s
2
1
S) = = I(256.68 Å)/I(491.45 Å) in Be-like SXIII reveals good agreement between theory and experiment, which provides observational support for the accuracy of the adopted atomic data. However, observed values of the electron density sensitive ratio R
2 = I(2s2p
1
P – 2s
2
1
S)/I(2p
2
3
P
2 - 2s2p
3
P
2) = = I(256.68 Å)/I(308.96 Å) all lie below the theoretical high density limit, which is probably due to blending in the 308.96 Å line. 相似文献
15.
The transport of thermal radiation has been considered within a finite slab which absorb and scatter anisotropically. The problem involves the space-dependent single-scattering albedow(x). Two approximations are taken forw(x). In the first it is represented in exponential form asw(x)=w
0 exp(–x/s), wherew
0 ands are given constants andx is the optical variable. The second approximation assumes the formw(x) =
r=0
R
d
r
*
p
r
(x/a), whered
r
*
are known expansion coefficients anda is the half optical thickness of the slab. Analytic expressions for the forward, backward radiation intensities and fluxes are given in each approximation. The solution of the linear transport equation is performed on the basis of integral Fourier transforms. 相似文献
16.
We perform an extensive linear investigation of the nonaxisymmetric disk modes referred to in the literature as P, I, and J modes in self-gravitating polytropic toroids with power law angular velocity distributions. For selected models, we also
follow the development of instability from the linear regime through the quasi-linear regime to deep into the nonlinear regime.
We consider modes with azimuthal dependence e
imφ
, where m is an integer and φ is the azimuthal angle. We find that instability sets in through m=2 barlike I modes at T/|W|∼0.16–0.18 depending upon the chosen angular velocity law where T is the rotational kinetic energy and W is the gravitational energy of the toroid. Instability in the barlike I mode peaks in strength around T/|W|=0.22–0.23 after which it weakens, eventually stabilizing around T/|W|∼0.25–0.26. One-armed modes (m=1 modes) become unstable just after instability in the m=2I modes sets in; instability in m=1 modes sets in at T/|W|∼0.19. They dominate the barlike I modes in toroids with T/|W|≳0.25. However, almost immediately after the m=1 mode overtakes the barlike I mode, higher-m
J modes appear. J modes with m=2, 3, and 4 become unstable for T/|W|≳0.25–0.26, 0.23–0.25, and 0.25–0.26, respectively. m≥3J modes dominate the m=1 mode in toroids with T/|W|≳0.27. As T/|W| increases further, nonaxisymmetric instability sets in through higher and higher m modes. We find quantitative agreement between the early nonlinear behavior of the tested unstable toroids and our linear
results. Quasi-linear modeling suggests that a gravitational self-interaction torque which arises early in the nonlinear regime
saturates growth of the mode and leads to significant transport of mass and angular momentum. Neither I mode nor J mode instabilities produce prompt fission in toroids. 相似文献
17.
In this paper, we have investigated that tilted Bianchi Type I cosmological models for stiff perfect fluid under a supplementary
condition A = B
n
between metric potentials, is not possible. The tilted solution is also not possible when we assume A = t
ℓ, B = t
m
, C = t
n
; ℓ, m and n are constants for ε = p. Thus to preserve tilted nature of model, we assume p = γε, 0 ≤ γ ≤ 1 (barotropic equation of state) for the case A = t
ℓ
B = t
m
and C = t
n
. The physical and geometrical aspects of the models are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
We have used photometric images of ten barred galaxies in the B and I bands to infer the geometrical and dynamical parameters of their bars: Their length, (R
bar), their strengths, (S
b), and their corotation radii, (R
CR).These parameters have been obtained studying azimuthal profiles from the B and I band images of the galaxies. We find that R
CR is in all cases slightly larger than R
bar, with mean values close to 1.2 R
bar. We have also found a dependence of the ratio R
CR/R
bar on S
bar.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Z. F. Gao N. Wang J. P. Yuan L. Jiang D. L. Song 《Astrophysics and Space Science》2011,332(1):129-138
In a superhigh magnetic field, direct Urca reactions can proceed for an arbitrary proton concentration. Since only the electrons
with high energy E (E>Q, Q is the threshold energy of inverse β-decay) at large Landau levels can be captured, we introduce the Landau level effect coefficient q and the effective electron capture rate Γ
eff
. By using Γ
eff
, the values of L
X
and L
ν are calculated, where L
X
and L
ν are the average neutrino luminosity of AXPs and the average X-ray luminosity of AXPs L
X
, respectively. The complete process of electron capture inside a magnetar is simulated numerically. 相似文献
20.
The evolution dH
R/dt of relative helicity H
R provides a gauge-invariant measure of the helicity flow across the open surface S
o of an active region. With the incompressible approximation, reformulation of the evolution reveals that it is determined not only by the widely used cross-helicity h
mvp=A
pv contributed by the vector potential A
p of a reference potential field B
p, where v is the fluid velocity, but by another cross-helicity h
mvo=A
ov contributed by the vector potential A
o of the open field B
o in the region as well. Only under two conditions, (1) A
p=A
(A
is the transverse component of A
o), (2) v
z=0 (v
z is the longitudinal component of v) or A
z=0 (A
z is the longitudinal component of A
o), can h
mvo be merged into h
mvp to give the pioneering dH
R/dt equation shown in Equation (4) of Berger (1984). Results show that h
mvo originates from vh
o (h
o=A
oB
o is the helicity density of the open field) and should also be considered in dealing with the development of relative helicity in active regions. Finally, the equation to calculate dH
R/dt in active regions is synthesized and presented. 相似文献