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1.
A model is presented for the generation and evolution of bump-in-tail driven Langmuir waves in the solar wind during type III emission, which removes a number of apparent inconsistencies between theory and observations. It is argued that there must be localized enhancements of f
b
/v
by a factor of 102 over the measured average values. Growth rates and energy densities of Langmuir waves are, therefore, considerably enhanced, permitting growth to overcome linear scattering losses, and also allowing nonlinear decay into ion-acoustic waves, in line with observations. Estimates are made of the probability distribution p(E), of wave field strengths E, based on linear and nonlinear wave-packet evolution, yielding p(E) E
–a, 3. This helps explain why very high values of E are rarely found in the measured spiky wave turbulence. 相似文献
2.
Michael Schulz 《Astrophysics and Space Science》1975,36(2):455-458
In the quasilinear theory of magnetospheric radial diffusion caused by fluctuating electrostatic (E) or magnetic (B) fields, the diffusion coefficientD
LLis proportional to the spectral density of E or B at the particle drift frequency 3/2. Since 3 varies withL at fixedM andJ (adiabatic invariants), the drift resonance =3 can be maintained only transiently, and therefore is not perfectly sharp. Its bandwidth * is approximately (16D
LL
/L
23)1/33. In magnetospheric radial diffusion caused mainly by electrostatic fluctuations, the value of *3 typically exceeds 0.4 for particle energiesE40 keV. However, the numerical value ofD
LLis correctly given (within 1% in all cases) by quasilinear theory because the spectrum of E is rather flat at resonance frequencies for which the bandwidth is an appreciable fraction of 3. (Numerical conclusions are based on a quasilinear model forD
LLused successfully by Cornwall in 1972.) 相似文献
3.
, , , . , (z103) - , - , , , 1 (z10). , . 相似文献
4.
Л. Г. Лукьялов 《Celestial Mechanics and Dynamical Astronomy》1976,13(4):455-464
, . . . .
Some asymptotic solutions in the restricted problem of three bodies by L. G. Lukjanov.
Some particular solutions of the plane restricted problem of three bodies in the form of Liapunov's series are obtained. These solutions asymptotically approach the Lagrange solutions. Convergence is proved.相似文献
5.
The power in the different modes of an expansion of the solar radial magnetic field at the surface in terms of Legendre polynomials,P , is calculated with the help of a solar dynamo model studied earlier. The model is of the Babcock–Leighton type, i.e., the surface eruptions of the toroidal magnetic field – through the tilt angle, , formed by the magnetic axis of a bipolar magnetic region with the east-west line – are the sources for the poloidal field. In this paper it is assumed that the tilt angle is subject to fluctuations of the form, = ()+ <> where <> is the average value and () is a random normal fluctuation with standard deviation which is taken from Howard's observations of the distribution of tilt angles. For numerical considerations, negative values of were not allowed. If this occurred, was recalculated. The numerical integrations were started with a toroidal magnetic field antisymmetric across the equator, large enough to generate eruptions, and a negligible poloidal field. The fluctuations in the tilt angle destroy the antisymmetry as time increases. The power of the antisymmetric modes across the equator (i.e., odd values of ) is concentrated in frequencies, p, corresponding to the cycle period. The maximum power lies in the =3 mode with considerable power in the =5 mode, in broad agreement with Stenflo's results who finds a maximum power at =5. For the symmetric modes, there is considerable power in frequencies larger than p, again in broad agreement with Stenflo's power spectrum. 相似文献
6.
The initial discovery of soft X-rays from Nova Muscae 1983 was followed by eight additional observations of the three brightest novae whose outburst stage coincided with the lifetime ofEXOSAT satellite; namely three more observations of Nova Muscae 1983, three observations of Nova Vulpeculae 1984#1 (PW Vul), and two observations of Nova Vulpeculae 1984#2. Through these observations we sampled the soft X-ray light curve of classical novae from optical maximum to 900 days after. The observations seem best explained by the constant bolometric luminosity model of a hot white dwarf remnant. Although the measurements suffer from limited statistics, very broad energy bandpass, and incomplete sampling of any single nova, their constraints on the theories of nova outburst are significant. One constraint is that the lifetime of the white dwarf remnant in Nova Muscae 1983 is 2 to 3 years, which leads to the conclusion that the burned envelope massM
burn should be of the order of
. The second constraint is that the maximum temperature, of the white dwarf remnant should approximately be within 200 000 K to 400 000 K. We estimate that a white dwarf remnant evolving like the central star of a planetary nebula, with core mass of 0.8 to 0.9M
, core luminosity of 2×104
L
, and envelope mass of 10–6
M
, can explain the general characteristics of the X-ray measurements for Nova Muscae 1983. In order to have 1.1M
core mass, estimated from the early observations of bolometric luminosity in the UV to infrared range, a wind withM5×10–7
M
yr–1 appears to be necessary. The few observations of Nova Vulpeculae 1984 #1 and Nova Vulpeculae 1984#2, during the first year after outburst, give a risetime and intensity that is consistent with a constant bolometric luminosity model.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F. R. G., 16–19 June, 1986. 相似文献
7.
The gravity potential of an arbitrary bodyT is expanded in a series of spherical harmonics and rigorous evaluations of the general termV
n
of the expansion are obtained. It is proved thatV
n
decreases on the sphere envelopingT according to the power law if the body structure is smooth. For a body with analytic structure,V
n
decreases in geometric progression. The exactness of these evaluations is proved for bodies having irregular and analytic structures. For the terrestrial planetsV
n
=O (n
–5/2).
I I V n IV n I . . IV n I . I. IV n =O(n –5/2 )相似文献
8.
F. Sibille Ph. Merlin I. Vauglin F. Billebeaud P. O. Lagage R. Jouan F. Lacombe P. Drossart J. Ph. Bernard 《Experimental Astronomy》1994,3(1-4):175-176
This paper presents the general features of the C10 camera, now in routine operation at the CFHT, with initial results on CVF observations of the C2H2 and C2H6 bands and the continuum in the atmospher e of Saturn. 相似文献
9.
High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 109 M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN. 相似文献
10.
The problem of single Compton scattering is considered and the resulting spectrum, angular distribution and polarization of scattered photons in a general case are obtained. The inverse Compton scattering (ICS) for arbitrary energies of electronsE and photons 0 is investigated in detail. In the case of isotropically-distributed initial photons and relativistic electrons, a strong rise of the scattered spectrum near the upper edge takes place, starting from the values of the characteristic parameterb4E
010 (in units of mc2=1). The energy-loss rate of relativistic electrons due to ICS is calculated. It is shown that the relativistic electrons of the energiesE100 MeV, when scattering on the X-rays with 0~10KeV, transmit the dominant part of their energy to the photons which fall after scattering into the energy range of the electrons (100 MeV).The radiation spectrum of ICS, as well as the energy-losses of relativistic electrons distributed by power-lawE
–, are calculated. The radiation spectrum reveals the power-law behaviour with the different indices in two limits: the dependence –(1)/2 at 01 gradually changes to –(+1) ln (0) law for 01. 相似文献
11.
Г. А. Гусзадян 《Astrophysics and Space Science》1979,62(1):35-44
(Kilyachkoet al., 1978) , . l ( I II). (Kilyachkoet al., 1978) : (1) 800 Å , , UV Cet. EV Lac; (2) UV Cet EV Lac 8000 Å , ; (3) 8000 Å . — MO-KS; (4) 1–3 m. 相似文献
12.
V. A. Brumberg L. S. Evdokimova V. I. Skripnichenko 《Celestial Mechanics and Dynamical Astronomy》1975,11(1):131-138
Based on a general planetary theory, the secular perturbations in the motion of the eight major planets (excluding Pluto) have been derived in polynomial form. The results are presented in the tables. The linear terms of second order with respect to the planetary masses and the nonlinear terms of first order up to the fifth (and partly seventh) degree with respect to eccentricities and inclinations were taken into account in the right-hand members of the secular system. Calculations were carried out by computer with the use of a system that performed analytic operations on power series with complex coefficients.
qA ( ). . ( ) . .相似文献
13.
( , 1977; , 1977). , , , . . 相似文献
14.
Masaya Saitou 《Astrophysics and Space Science》1989,162(1):47-56
Some peculiarities in the behaviour of a model self-gravitating system described by hydrodynamical equations and isothermal equation of state connected with the presence of thermodynamical fluctuations in real systems were investigated in numerical experiment. The values of density and velocity , , respectively, were computed by numerical code perturbed on each time-step and in each computational cell by random values , for modeling such fluctuations. Perturbed values
i
=
i
+
i
,v
i
=
i
+ v
i
were used to initiate the next step of computations. This procedure is equivalent to an introduction into original hydrodynamical equations of Langevin sources which are random functions. It is shown that these small fluctuations (= v =0,2 =v
2 = 10–8) grow many times in marginally-stable state. 相似文献
15.
Hong Wei Li 《Solar physics》1986,104(1):131-136
The variations of the growth rates of ECM at first four harmonics in X-, Z-, and O-modes excited by a hollow beam distribution of weakly relativistic electrons with a parameter
p
/
e
are presented in this paper. The results show that the second harmonic of ECM in X-mode dominates the instability if < 1, and if 1.2 , 2 or 2.2 3 the third or fourth harmonic will dominate. The second and third harmonics of Z-mode waves grow faster only if 2 2.2 and 3 3.2, respectively, so it would not be a competition in most cases. It is suggested that the ECM emission at these harmonics in X-mode is a possible mechanism to produce solar spike emissions with high brightness temperature at shorter and longer decimetric wavelengths.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.On leave from the Department of Astronomy, Nanjing University, Nanjing, The People's Republic of China. 相似文献
16.
Lockwood, Stamper, and Wild (1999) argued that the average strength of the magnetic field of the Sun has doubled in the last 100 years. They used an analysis of the geomagnetic index aa. We calculated the area of polar zones of the Sun, A
pz, occupied by unipolar magnetic field on H synoptic magnetic charts, following Makarov (1994), from 1878 to 2000. We found a gradual decrease of the annual minimum latitude of the high-latitude zone boundaries, 2m, of the global magnetic field of the Sun at the minimum of activity from 53° in 1878 down to 38° in 1996, yielding an average decrease of 1.2° per cycle. Consequently the area of polar zones A
pz of the Sun, occupied by unipolar magnetic field at the minimum activity, has risen by a factor of 2 during 1878–1996. This means that the behavior of the index aa and consequently the magnetic flux from the Sun may be explained by an increase of the area of polar caps with roughly the same value of the magnetic field in this period. The area of the unipolar magnetic field at the poles (A
pz) may be used as a new index of magnetic activity of the Sun. We compared A
pz with the aa, the Wolf number W and A* -index (Makarov and Tlatov, 2000). Correlations based on `11-year' averages are discussed. A temperature difference of about 1° between the Maunder Minimum and the present time was deduced. We have found that the highest latitude of the polar zone boundaries of the large-scale magnetic field during very low solar activity reaches about 60°, cf., the Maunder Minimum. It is supposed that the 2m-latitude coincides with the latitude where r=0, with (r,) being the angular frequency of the solar rotation. The causes of the waxing and waning of the Sun's activity in conditions like Maunder Minimum are discussed. 相似文献
17.
Г. И. Ширмин 《Celestial Mechanics and Dynamical Astronomy》1975,11(4):483-515
1937 - (, 1938). , , , , . , . . (, 1938), , . - (, 1938; Szebehely, 1967)., , . . - (, 1938), . — — . , , . , . . , . , , . . (, 1944). , .
In 1937, the Celestial Mechanics and Cosmogony section of the Sternberg State Astronomical Institute undertook the task of evaluating the Gylden-Moulton hypothesis on the origin of the Gegenshein from the standpoint of celestial mechanics. That investigation, which the authors themselves considered preliminary, contains nonetheless a series of important results. For example, G. N. Duboshin showed that in the planar, circular, restricted three-body problem, periodic motion of finite amplitude in the neighborhood of a collinear libration point is unstable according to Lyapunov's criterion both in the proper and in the orbital sense. The latter result is incompatible with the above named hypothesis, and thus appears as one of the serious objections among the many known negative conclusions relative to the existence of the Gylden-Moulton cluster.Unfortunately, most of the specific problems which arose in the above named research have not been considered since. One of these, the problem of the stability of three-dimensional periodic orbits in the neighborhood of a collinear libration point is solved in the present paper, within the limits of the three-dimensional, circular, restricted, three-body problem. Major attention is given to the investigation of stability in the orbital sense, since in the proper sense all orbits are unstable according to Lyapunov theory. It is shown that in order to resolve the question of stability, it is sufficient to consider the equations in their variational form. Analysis of the roots of the corresponding characteristic equations determines the orbital stability of planar and three-dimensional solutions, which later can be confirmed by calculation of the characteristic exponents appearing in the periodic solutions of the N. A. Artemiev method. Finally, the possibility of conditional stability in the linear approximation is proved.相似文献
18.
The character of the yearly average and secular variations of the intensity of the radio emission of Cassiopeia A is discussed on the basis of multiyear observations (1953-2001) made at Byurakan Astrophysical Observatory and the Institute of Radiophysics and Electronics. It is shown that in this period the intensity of the radio emission of Cassiopeia A has decreased by about 34%, at a yearly average rate of 0.7%. 相似文献
19.
, ii (2000–3000 Å) i . , i . i (. 2). i i i i + ( 7–10). ii (. 13). ii i i (, 2400 Å) (. 14 15). i i i , iu , i (. 1). i i ii i i . . 相似文献
20.
, , , . () , . , . 相似文献