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1.
We analyze here the behavior of the magnitudes of the F1 and E peaks of the electron density profiles measured by the Radio Science Subsystem of the Mars Global Surveyor spacecraft, as a function of solar zenith angle χ and solar flux. For each of the 658 days of data in the six occultation seasons in the northern hemisphere, we choose one profile to analyze, which is that for which the F1 peak is the median value. We assume that the variations of the measured peak densities can be represented as Aa(cosχ) and as Bb(F10.7), where F10.7 is the usual solar flux proxy, appropriately shifted to the orbital position of Mars. To minimize the effect of solar activity, we divide the data into 6 F10.7 bins, fit the data in each bin, and derive the values of the exponent a and the coefficient AF10.7 for each bin. The median values that we derive for the exponent a is 0.46 for the F1 peak, and 0.395 for the E peak. To minimize the effect of SZA, we divide the data into eight SZA bins, and derive the exponent b and the coefficient Bχ for each SZA bin. We argue that the last three SZA bins should be excluded because the fits were poor, due partly to the small number of data points in each of these bins. If we do so, the median values of b that we derive are 0.27 and 0.40 for the F1 and E peaks, respectively. Finally we derive a 3-parameter fit to all the data, which expresses the variability of the peak densities as a function of a′(cosχ) and b′(F10.7) simultaneously. The fitted values of the exponents a′ and b′ for the F1 peak are 0.45 and 0.26, respectively; for the E peak, the values are 0.39 and 0.46, respectively. We compare our results to Chapman theory, and to those of other investigators. 相似文献
2.
Three wavelet functions: the Morlet wavelet, the Paul wavelet, and the DOG wavelet have been respectively performed on both
the monthly Wolf sunspot numbers (Rz) from January 1749 to May 2004 and the monthly group sunspot numbers (Rg) from June 1795 to December 1995 to study the evolution of the Gleissberg and Schwabe periods of solar activity. The main
results obtained are (1) the two most obvious periods in both the Rz and Rg are the Schwabe and Gleissberg periods. The Schwabe period oscillated during the second half of the eighteenth century and
was steady from the 1850s onward. No obvious drifting trend of the Schwabe period exists. (2) The Gleissberg period obviously
drifts to longer periods the whole consideration time, and the drifting speed of the Gleissberg period is larger for Rz than for Rg. (3) Although the Schwabe-period values for Rz and Rg are about 10.7 years, the value for Rz seems slightly larger than that for Rg. The Schwabe period of Rz is highly significant after the 1820s, and the Schwabe period of Rg is highly significant over almost the whole consideration time except for about 20 years around the 1800s. The evolution
of the Schwabe period for both Rz and Rg in time is similar to each other. (4) The Gleissberg period in Rz and Rg is highly significant during the whole consideration time, but this result is unreliable at the two ends of each of the time
series of the data. The evolution of the Gleissberg period in Rz is similar to that in Rg. 相似文献
3.
The distribution of monthly counts of grouped solar flares N
f
has been studied for the time period 1967–1985 and they have been compared to other solar activity index R
z
, F
2800, and F
3750 i.e. intensities of solar radio flux at 2800 MH
z
and 3750 MH
z
. Seasonal variations have been found in the monthly distribution of solar flares.We have also studied the variation of the correlation coefficient for every year between N
F
and R
z
for the time period 1967–1985. The distribution of monthly counts of grouped solar flares N
f
has also been compared to the number at high velocity solar-wind streamers for the same period. 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.
Special analytical solutions are determined for restricted, coplanar, four-body equal mass problems, including the Caledonian problem, where the masses Mi = M for i = 1,2,3,4. Most of these solutions are shown to reduce to the Lagrange solutions of the Copenhagen problem of three bodies by reducing two of the masses (mi = m for i = 1,2) in the four-body equal mass problem to zero while maintaining their equality of mass. In so doing, families of special solutions to the four-body problem are shown to exist for any value of the mass ratio μ = m/M. 相似文献
6.
We derive general results on the existence of stationary configurations for N co-orbital satellites with small but otherwise arbitrary masses m
i
, revolving on circular and planar orbits around a massive primary. The existence of stationary configurations depends on
the parity of N. If N is odd, then for any arbitrary angular separation between the satellites, there always exists a set of masses (positive or
negative) which achieves stationarity. However, physically acceptable solutions (m
i
> 0 for all i) restrict this existence to sub-domains of angular separations. If N is even, then for given angular separations of the satellites, there is in general no set of masses which achieves stationarity. The case N=3 is treated completely for small arbitrary satellite masses, giving all the possible solutions and their stability, to within
our approximations. 相似文献
7.
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
8.
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
9.
P. S. Negi 《Astrophysics and Space Science》2011,332(1):145-153
We construct for the first time, the sequences of stable neutron star (NS) models capable of explaining simultaneously, the
glitch healing parameters, Q, of both the pulsars, the Crab (Q≥0.7) and the Vela (Q≤0.2), on the basis of starquake mechanism of glitch generation, whereas the conventional NS models cannot give such consistent
explanation. Furthermore, our models also yield an upper bound on NS masses similar to those obtained in the literature for
a variety of modern equations of state (EOSs) compatible with causality and dynamical stability. If the lower limit of the
observational constraint of (i) Q≥0.7 for the Crab pulsar and (ii) the recent value of the moment of inertia for the Crab pulsar (evaluated on the basis of
time-dependent acceleration model of the Crab Nebula), I
Crab,45≥1.93 (where I
45=I/1045 g cm2), both are imposed together on our models, the models yield the value of matching density, E
b
=9.584×1014 g cm−3 at the core-envelope boundary. This value of matching density yields a model-independent upper bound on neutron star masses,
M
max≤2.22M
⊙, and the strong lower bounds on surface redshift z
R
≃0.6232 and mass M≃2.11M
⊙ for the Crab (Q≃0.7) and the strong upper bound on surface redshift z
R
≃0.2016, mass M≃0.982M
⊙ and the moment of inertia I
Vela,45≃0.587 for the Vela (Q≃0.2) pulsar. However, for the observational constraint of the ‘central’ weighted mean value Q≈0.72, and I
Crab,45>1.93, for the Crab pulsar, the minimum surface redshift and mass of the Crab pulsar are slightly increased to the values
z
R
≃0.655 and M≃2.149M
⊙ respectively, whereas corresponding to the ‘central’ weighted mean value Q≈0.12 for the Vela pulsar, the maximum surface redshift, mass and the moment of inertia for the Vela pulsar are slightly decreased
to the values z
R
≃0.1645, M≃0.828M
⊙ and I
Vela,45≃0.459 respectively. These results set an upper and lower bound on the energy of a gravitationally redshifted electron-positron
annihilation line in the range of about 0.309–0.315 MeV from the Crab and in the range of about 0.425–0.439 MeV from the Vela
pulsar. 相似文献
10.
The distribution of pairwise distances f(l) for different dependences r(z) of the metric distance is used to reveal inhomogeneities in the spatial distribution of 201 long (T
90>2s) gamma-ray bursts with measured redshifts z. For a fractal set with dimensionality D, this function behaves asymptotically as f(l) ∼ l
D−1 for small l. Signs of fractal behavior with dimensionality D = 2.2–2.5 show up in all the models considered for the spatial distribution of the gamma-ray bursts. Several spatially distinct
groups of gamma-ray bursts are identified. The group with equatorial coordinates ranging from 23h56m to 0h49m and δ from +19° to +23° with redshifts of 0.81–0.94 is examined separately. 相似文献
11.
It is shown that it can be useful to incorporate the orbital period P as an additional parameter into the Kukarkin-Parenago relationship. Then it turns out that the relationship splits into two, one holding for objects above and the other for objects below the well-known and much-discussed period gap between 2.2 and 2.8 hours A = -2.03 + 2.26 log C + 8.80 log P for P > 2.2 h A = 2.07 + 2.46 log C - 3.68 log P for P > 2.8 h (A amplitude (mag), C cycle length (d), P orbital period (h)). Future theories of the dwarf nova phenomenon and the origin of the period gap will have to deal with this. 相似文献
12.
In this study, we consider a flat Friedmann-Robertson-Walker (FRW) universe in the context of Palatini f(R) theory of gravity. Using the dynamical equivalence between f(R) gravity and scalar-tensor theories, we construct a point Lagrangian in the flat FRW spacetime. Applying Noether gauge symmetry approach for this f(R) Lagrangian we find out the form of f(R) and the exact solution for cosmic scale factor. It is shown that the resulting form of f(R) yield a power-law expansion for the scale factor of the universe. 相似文献
13.
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
14.
Yu. A. Fadeyev 《Astronomy Letters》2011,37(6):403-413
Instability of population I (X = 0.7, Z = 0.02) massive stars against radial oscillations during the post-main-sequence gravitational contraction of the helium core
is investigated. Initial stellar masses are in the range 65M
⊙ ≤ M
ZAMS ≤ 90M
⊙. In hydrodynamic computations of self-exciting stellar oscillations we assumed that energy transfer in the envelope of the
pulsating star is due to radiative heat conduction and convection. The convective heat transfer was treated in the framework
of the theory of time-dependent turbulent convection. During evolutionary expansion of outer layers after hydrogen exhaustion
in the stellar core the star is shown to be unstable against radial oscillations while its effective temperature is T
eff > 6700 K for M
ZAMS = 65M
⊙ and T
eff > 7200 K for M
ZAMS = 90M
⊙. Pulsational instability is due to the κ-mechanism in helium ionization zones and at lower effective temperature oscillations decay because of significantly increasing
convection. The upper limit of the period of radial pulsations on this stage of evolution does not exceed ≈200 day. Radial
oscillations of the hypergiant resume during evolutionary contraction of outer layers when the effective temperature is T
eff > 7300 K for M
ZAMS = 65M
⊙ and T
eff > 7600 K for M
ZAMS = 90M
⊙. Initially radial oscillations are due to instability of the first overtone and transition to fundamental mode pulsations
takes place at higher effective temperatures (T
eff > 7700 K for M
ZAMS = 65M
⊙ and T
eff > 8200 K for M
ZAMS = 90M
⊙). The upper limit of the period of radial oscillations of evolving blueward yellow hypergiants does not exceed ≈130 day.
Thus, yellow hypergiants are stable against radial stellar pulsations during the major part of their evolutionary stage. 相似文献
15.
The cosmological reconstruction of modified F(R) and F(G)F(\mathcal{G}) gravities with agegraphic dark energy (ADE) model in a spatially flat universe without matter field is investigated by using
e-folding “N” as a forward way. After calculating a consistent F(R) in ADE’s framework, we obtain conditions for effective equation of state parameter w
eff, and see that reconstruction is possible for both phantom and non-phantom era. These calculations also are done for F(G)F(\mathcal{G}) gravity and the condition for a consistent reconstruction is obtained. 相似文献
16.
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
17.
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
18.
Peter Wasilewski 《Earth, Moon, and Planets》1974,11(3-4):357-367
Rotational Magnetic hysteresis (W
R
) curves for lunar soils 10084, 12070, 14259, and rock 14053, have been published. There is no adequate explanation to date for the observed largeW
R
at high fields. Lunar rock magnetism researchers consider fine particle iron to be the primary source of stable magnetic remanence in lunar samples. Iron has cubic anisotropy with added shape anisotropy for extreme particle shapes. The observed high fieldW
R
must have its source in uniaxial or unidirectional anisotropy. This implies the existence of minerals with uniaxial anisotropy or exchange coupled spin states. Therefore, the source of this observed high fieldW
R
must be identified and understood before serious paleointensity studies are made. It is probable that the exchange coupled spin states and/or the source of uniaxial anisotropy responsible for the high fieldW
R
might be influenced by the lunar surface diurnal temperature cycling. The possible sources of high fieldW
R
in lunar samples are presented and considered. 相似文献
19.
Periodic polar motions caused by ocean tides are predicted. In the Liouville equations for rotational motion the complete excitation functions for the ocean tides have to be used. This does not depend on the fact that hydrodynamical ocean tide models do not consider the centrifugal acceleration. The observable polar motion of the Celestial Ephemeris Pole CEP (more exactly: the terrestrial location of the CEP) is tabulated for the ten ocean tides M2, S2, N2, K1, O1, P1, M f, M f′, M m, Ssa. Typical amplitudes for the largest ocean tides are 0.4 milliarcseconds. This is within the reach of geodetic VLBI and SLR observations. 相似文献
20.
Green's Theorem is developed for the spherically-symmetric steady-state cosmic-ray equation of transport in interplanetary space. By means of it the momentum distribution functionF
o(r,p), (r=heliocentric distance,p=momentum) can be determined in a regionr
arrbwhen a source is specified throughout the region and the momentum spectrum is specified on the boundaries atr
a
andr
b
. Evaluation requires a knowledge of the Green's function which corresponds to the solution for monoenergetic particles released at heliocentric radiusr
o
, Examples of Green's functions are given for the caser
a
=0,r
b
= and derived for the cases of finiter
a
andr
b
. The diffusion coefficient is assumed of the form = o(p)r
b
. The treatment systematizes the development of all analytic solutions for steady-state solar and galactic cosmic-ray propagation and previous solutions form a subset of the present solutions. 相似文献