共查询到20条相似文献，搜索用时 171 毫秒
1.
Yu. A. Rylov 《Astrophysics and Space Science》1988,143(2):269-300
The model of the pulsar magnetosphere filled with massless charged particles (rest massm=0) is considered. Such a representation is valid in the case, when e mc
2, where is a characteristic potential difference in the pulsar magnetosphere. This inequality takes place almost everywhere in the pulsar magnetosphere. The gas of charged massless particles can be found in two different phases: (1) dynamical phase (DP), when the particles move with nonvanishing energy along some base lines, determined by the electromagnetic field only, (2) statical phase (SP), when the particles have vanishing energy =0. Even in the simplest axially-symmetric case the pulsar magnetosphere occurs to be divided into regions of different types: (a) the accelerating regions (DP-regions), containing only DP, (b) the capture regions, containing only SP, (c) leaky capture regions, where DP moves through SP. The leaky capture regions are the active regions, which are responsible for the pulsar radio-emission, In the paper the mathematical technique of the massless approximation has been developed. The properties of the capture region has been investigated. The problem of axially-symmetric pulsar magnetosphere has been stated mathematically. The massless approximation permits to substitute some differential equations by the algebraic ones, and to simplify the statement of the problem. 相似文献
2.
There are indications that less than 10–3 of the spin-down energy of the millisecond pulsar PSR 1937+214 emerges as electromagnetic radiation. The implications of this result are discussed. The surface magnetic field would then be 107 G, making the pulsar optically undetectable, and casting aspersions on the accretion disc spin-up neutron star models for the pulsar. The pulsar should have an equatorial ellipticity 10–9, which can be accounted for if the equatorial magnetic field departs from axisymmetry by one part in 103. 相似文献
3.
F. C. Michel 《Astrophysics and Space Science》1980,72(1):175-181
We conclude that the magnetospheric structure around an aligned rotating magnetized neutron star, in the case of a completely charge-separated plasma, consists of a dome of charge about the polar caps and an equatorial disk of opposite charge which, together, entirely envelope the surface but do not fill the magnetosphere. Although the aligned rotator is a standard model for analyzing pulsar emission, the magnetosphere we obtain need not emit particles and need not generate a stellar wind, contrary to previous expectations. Pair production only seems to modify the detailed shape of the dome and disk, such modification serving to shut off further pair production. Such a magnetohydrodynamically inactive object may have difficulty simulating pulsar emission.Research support in part by the National Science Foundation under grant AST 77-22675. 相似文献
4.
The influence of the Landau-Pomeranchuk effect on the development of a shower generated by ultrarelativistic particles bombarding the surface of a pulsar is discussed. Because of this effect, the path length of the shower increases while low-energy photon generation is strongly suppressed. In view of this, the mechanism of pair production suggested by Cheng, Ruderman, and Jones for the pulsar magnetosphere, may be essential only for pulsars whose magnetic field intensity at the surface lies in a relatively narrow range of aroundB 1012 G. 相似文献
5.
Ian W. Walker A. Gordon Emslie Archie E. Roy 《Celestial Mechanics and Dynamical Astronomy》1980,22(4):371-402
An expansion of the force function ofn-body dynamical systems, where the equations of motion are expressed in the Jacobian coordinate system, is shown to give rise naturally to a set of (n–1) (n–2) dimensionless parameters
ki
li
{i = 2,...,n;k = 2,...,i – 1 (i 3);l =i + 1,...,n (i n – 1)}, representative of the size of the disturbances on the Keplerian orbits of the various bodies. The expansion is particularized to the casen=3 which involves the consideration of only two parameters
23 and
32. Further, the work of Szebehely and Zare (1977) is reviewed briefly with reference to a sufficient condition for the stability of corotational coplanar three-body systems, in which two of the bodies form a binary system. This condition is sufficient in the sense that it precludes any possibility of an exchange of bodies, i.e. Hill type stability, however, it is not a necessary condition. These two approaches are then combined to yield regions of stability or instability in terms of the parameters
23 and
32 for any system of given masses and orbital characteristics (neglecting eccentricities and inclinations) with the following result: that there is a readily applicable rule to assess the likelihood of stability or instability of any given triple system in terms of
23 and
32.Treating a system ofn bodies as a set of disturbed three-body systems we use existing data from the solar system, known triple systems and numerical experiments in the many-body problem to plot a large number of triple systems in the
23,
32 plane and show the results agree well with the
23,
32 analysis above (eccentricities and inclinations as appropriate to most real systems being negligible). We further deal briefly with the extension of the criteria to many-body systems wheren>4, and discuss several interesting cases of dynamical systems. 相似文献
6.
E. E. Shnol 《Celestial Mechanics and Dynamical Astronomy》1984,33(2):159-167
The equilibrium point O of an autonomous Hamiltonian system of two degrees of freedom is considered for small-oscillation frequencies related as 2=21+. If under the precise resonance (=0) the equilibrium is unstable, the inner diameter () of the domain of stability containing the point O is estimated. It is shown that for the normalized variables ()/b where b is the corresponding resonance coefficient. The estimates () for other main resonances are reported. 相似文献
7.
Hongnan Zhou 《Earth, Moon, and Planets》1989,46(3):233-241
We devised a numerical model of planetary ring in which the inelastic collision and the gravitation between ring particles are considered. We adopt Hill's equations and the differential algorithm of circular mesh for computation of the particle orbits. The evolutional processes are presented for different coefficient of restitution and dynamical optical depth . The results show that the semi-major axis and eccentricity of the ring particles are changed with and . We compute the average energies transferred and loss in inelastic collisions for various values of the parameters. The dynamical equilibrium properties are discussed in the different cases. 相似文献
8.
The effect of small perturbations and in the coriolis and the centrifugal forces respectively on the stability of the triangular points in the restricted problem of three bodies with variable mass has been studied. It is found that the range of stability of triangular points increases or decreases depending upon whether the perturbation point (, ) lies in one or the other of the two parts in which the (, ) plane is divided by the line J8–J9=0 where J8 and J9 depend upon , the constant due to the variation in mass governed by Jeans' law. 相似文献
9.
The location and the stability of the libration points in the restricted problem have been studied when small perturbation and are given to the Coriolis and the centrifugal forces respectively. It is seen that the pointsL
4 andL
5 form nearly equilateral triangles with the primaries and the pointsL
1,L
2,L
3 remain collinear. It is further observed that for the pointsL
4 andL
5, the range of stability increases or decreases depending upon whether the point (, ) lies in one or the other of the two parts in which the (, ) plane is divided by the line 36-19=0 and the stability of the collinear points is not influenced by the perturbations and they remain unstable. 相似文献
10.
W. E. Alnaser 《Earth, Moon, and Planets》1990,48(2):177-181
The clear sky emissivity 0 and the ground emissivity
g
in Bahrain is studied. The study reveals that the annual value of 0 is 0.88 ± 0.039 relating to the maximum and the minimum values in August and February, respectively. Meanwhile, the annual value of
g
is 0.338 ± 0.228, where the maximum and the minimum values are in July and January, respectively. These two parameters are related to the transmittance factor . 相似文献
11.
The motion and radiation of relativistic particles with radiation reaction in a strong magnetic field has been considered. The kinetic equation determining the relaxation of the distribution function with radiation reaction has been investigated. The universal one-dimensional distribution function is found to which any isotropic ultrarelativistic distribution in a strong magnetic field is relaxed. It is of power type –3 for ultrarelativistic energies mc
2. Estimations are made which indicate that under the pulsar conditions the one-dimensional electron distribution function is likely formed due to radiation losses while for ions the one-dimensionalization is associated with the conservation of the adiabatic invariant. 相似文献
12.
The nonlinear evolution of waves in a low-density plasma in a strong magnetic field is investigated on the basis of the Chew-Goldberger-Low approximation. The nonlinear effects are found to be essentially different for the magneto-acoustic and Alfvén modes. For the magnetic-acoustic mode, waveform distortion occurs at order 2 (where is a measure of the linear wave amplitude) and shock formation occurs over a time-scale of order –1. For the Alfvén wave, modulation occurs at order 3 and shock formation over a time-scale of order –2. The nature of the waveform distortion is qualitatively different for the two modes. 相似文献
13.
The variation of the scattering index parameter () with galactic latitude and longitude is compared with the absorption measurements as well as electron density variations in the intersteller medium (ISM). We thus extend an earlier work (Okeke, 1981) by showing that the existence of a three-phase structure for the ISM could be responsible for the random variation of , which possibly is a good indicator of the nature of the ISM. 相似文献
14.
In the theory of supergravity (N=1), the supersymmetric version of general relativity, and for the Kasner cosmological model (Bianchi type I) we find a non-trivial solution (for the metric and spinor-vector) under the most simple assumption =11 + 22; 12+21=0 and for a special choosed gaugeN=1,N
j=0, 0=0. This method could be also applied to other cosmological metrics and extended to enlarged Grassmann basis.O. Obregón was partially supported by the Alexander von Humboldt Stiftung. 相似文献
15.
D. Gillon 《Astrophysics and Space Science》1981,77(1):111-119
We consider self-gravitating one-dimensional stellar systems governed by the coupled equations of Vlasov and Poisson. Using Bartholomew formalism we first make completely explicit the marginal mode which is a displacement mode of the system, and then we use it to show the stability of one-dimensional systems when their distribution functionF depending on the energy satisfies the sufficient condition of stability dF/d<0. 相似文献
16.
F.T. Gratton G. Gnavi R.M.O. Galvão L. Gomberoff 《Astrophysics and Space Science》1997,256(1-2):311-319
We study the modulational instability of an electron-positron plasma with relativistic temperatures and phonon damping. It is shown that when the phonon damping is O(1) or O(), a modulational instability appears even for classical temperatures. When the phonon damping is O(2)), we find that in the non-relativistic limit, previous results are recovered, and for ultrarelativistic temperatures, the instability occurs in a wider band around the relativistic plasma frequency. 相似文献
17.
G. E. O. Giacaglia 《Celestial Mechanics and Dynamical Astronomy》1971,4(3-4):468-489
We study the linear stability of the triangular points in the elliptic restricted problem by determining the characteristic exponents with a convergent method of iteration which in essence was introduced by Cesari (1940). We obtain the general term of such exponents as a power series in the eccentricity of the primaries, valid for sufficiently small and at all values of except one in the interval of stability of the circular problem. 相似文献
18.
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
19.
P. G. D. Barkham V. J. Modi A. C. Soudack 《Celestial Mechanics and Dynamical Astronomy》1977,15(1):5-20
A small particle moves in the vicinity of two masses, forming a close binary, in orbit about a distant mass. Unique, uniformly valid solutions of this four-body problem are found for motion near both equilateral triangle points of the binary system in terms of a small parameter , where the primaries move in accordance with a uniformly-valid three-body solution. Accuracy is maintained within a constant errorO(8), and the solutions are uniformly valid as tends to zero for time intervalsO(–3). Orbital position errors nearL
4 andL
5 of the Earth-Moon system are found to be less than 5% when numerically-generated periodic solutions are used as a standard of comparison. 相似文献
20.
Maxim Lyutikov 《Astrophysics and Space Science》1998,264(1-4):411-421
A theory of pulsar radio emission generation, in which the observed waves are produced directly by the maser-type plasma instabilities
on the anomalous cyclotron-Cherenkov resonance
and the Cherenkov-drift resonance
, is capable of explaining the main observational characteristics of pulsar radio emission. The instabilities are due to the
interaction of the fast particles of the primary beam and from the tail of the distribution with the normal modes of a strongly
magnetized one-dimensional electron-positron plasma. The waves emitted at these resonances are vacuum-like electromagnetic
waves that may leave the magnetosphere directly. The cyclotron-Cherenkov instability is responsible for core emission pattern
and the Cherenkov-drift instability produces conal emission. The conditions for the development of the cyclotron-Cherenkov
instability are satisfied for the both typical and millisecond pulsars provided that the streaming energy of the bulk plasma
is not very high γ
p
= 5 ÷ 10. In a typical pulsar the cyclotron-Cherenkov and Cherenkov-drift resonances occur in the outer parts of magnetosphere
at r
res
≈ 109cm. This theory can account for various aspects of pulsar phenomenology including the morphology of the pulses, their polarization
properties and spectral behavior.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献