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1.
Several of the exotic supernova remnants are re-interpreted as pulsar-illuminated former windzones. The class of supernova remnants thus splits into (i) (the usual) shell remnants and (ii) pulsar nebulae in which a (fairly young) pulsar blows its relativistic wind into its low-density environs. 相似文献
2.
G. Contopoulos 《Celestial Mechanics and Dynamical Astronomy》1986,38(1):1-22
We study the bifurcations of families of double and quadruple period orbits in a simple Hamiltonian system of three degrees of freedom. The bifurcations are either simple or double, depending on whether a stability curve crosses or is tangent to the axis b=–2. We have also generation of a new family whenever a given family has a maximum or minimum or .The double period families bifurcate from simple families of periodic orbits. We construct existence diagrams to show where any given family exists in the control space (, ) and where it is stable (S), simply unstable (U), doubly unstable (DU), or complex unstable (), We construct also stability diagrams that give the stability parameters b1 and b2 as functions of (for constant ), or of (for constant ).The quadruple period orbits are generated either from double period orbits, or directly from simple period orbits (at double bifurcations). We derive several rules about the various types of bifurcations. The most important phenomenon is the collision of bifurcations. At any such collision of bifurcations the interconnections between the various families change and the general character of the dynamical system changes. 相似文献
3.
Quasi-steady high-temperature current sheets are an energy source during the main or hot phase of solar flares. Such sheets are shown to be stabilized with respect to the tearing instability by a small transverse component of magnetic field existing in the sheets. 相似文献
4.
C. Martin Gaskell 《Astrophysics and Space Science》1982,82(1):247-248
The reported correlation between the absorption-line of emission-line redshifts of quasars is shown to be due to selection effects and thus to favour neither the intrinsic nor intervening hypotheses for the origin of quasar absorption lines. 相似文献
5.
P. G. Kazantzis 《Astrophysics and Space Science》1979,61(2):477-486
Families of three-dimensional axisymmetric periodic orbits are determined numerically in the Sun-Jupiter case of the restricted three-body problem. These families bifurcate from the vertical-critical orbits (v = 1,b
v = 0) of the basic plane familiesi andI. Further the predictor-corrector procedure employed to reveal these families has been described and interesting numerical results have been pointed out. Also, computer plots of the orbits of these families have been shown in conical projections. 相似文献
6.
A model of interplanetary and coronal magnetic fields 总被引：5，自引：0，他引：5
A model of the large-scale magnetic field structure above the photosphere uses a Green's function solution to Maxwell's equations. Sources for the magnetic field are related to the observed photospheric field and to the field computed at a source surface about 0.6 R
above the photosphere. The large-scale interplanetary magnetic field sector pattern is related to the field pattern at this source surface. The model generates magnetic field patterns on the source surface that compare well with interplanetary observations. Comparisons are shown with observations of the interplanetary magnetic field obtained by the IMP-3 satellite. 相似文献
7.
We numerically study the bifurcations of two nonlinear maps, with the same linear part, which depend on a parameter namely the Hénon quadratic map and the so called beam-beam map. Many families of periodic orbits which bifurcate from the central family, are studied. Each family undergoes a sequence of period doubling bifurcations in the quadratic map, But the behavior of the beam-beam map is completely different. Inverse bifurcations occur in both maps. But some families of the same type which bifurcate inversely in the quadratic map do not bifurcate inversely in the beam-beam map, even though both maps have common linear part. 相似文献
8.
Formulae containing the elements of the variational matrix are obtained which determine the linear iso-energetic stability parameters of periodic orbits of the general three-body problem. This requires the numerical integration of the variational equations but produces the stability parameters with the effective accuracy of the numerical integration. The procedure is applied for the determination of horizontally critical orbits among the members of sets of vertical-critical periodic orbits of the threebody problem. These critical-critical orbits have special importance as they delimit the regions in the space of initial conditions which correspond to possibly stable three-dimensional periodic motion of low inclination. 相似文献
9.
J. A. Adam 《Solar physics》1977,52(2):293-307
It is shown that the singular behaviour exhibited by a solution of the magnetoatmospheric wave equation for motion in the presence of a horizontal magnetic field is a special case of the valve type critical level discussed by Acheson (1973), with the difference that the valve effect does not strictly occur; waves are captured as they approach the singular level from either side and are neither reflected or transmitted, but constrained to propagate along the field line. This effect is also likely to occur for purely vertical fields. The possible importance of such critical levels to solar physics is discussed. 相似文献
10.
C. de Jager 《Astrophysics and Space Science》1978,59(1):165-170
Observations related to the photospheric velocity field of Cephei can be interpreted as follows: during the whole cycle of pulsations the only motion form in the atmosphere is a wave motion with a nearly constant full amplitude of approximately 15 km s–1, and a wavelength of about 106 km (which are quantities, about equal to the amplitudes of pulsational velocity and radius of the star). There are no significant small-scale turbulent velocity components. The microturbulent and macroturbulent velocities, as derived from spectral line observations, are fully compatible with this picture. 相似文献
11.
Part I gives a survey of the drastic revision of cosmic plasma physics which is precipitated by the exploration of the magnetosphere throughin situ measurements. The pseudo-plasma formalism, which until now has almost completely dominated theoretical astrophysics, must be replaced by an experimentally based approach involving the introduction of a number of neglected plasma phenomena, such as electric double layers, critical velocity, and pinch effect. The general belief that star light is the main ionizer is shown to be doubtful; hydromagnetic conversion of gravitational and kinetic energy may often be much more important.In Part II the revised plasma physics is applied to dark clouds and star formation. Magnetic fields do not necessarily counteract the contraction of a cloud; they may just as well pinch the cloud. Magnetic compression may be the main mechanism for forming interstellar clouds and keeping them together.Part III treats the formation of stars in a dusty cosmic plasma cloud. Star formation is due to an instability, but it is very unlikely that it has anything to do with the Jeans instability. A reasonable mechanism is that the sedimentation of dust (including solid bodies of different size) is triggering off a gravitationally assisted accretion. A stellesimal accretion analogous to the planetesimal accretion leads to the formation of a star surrounded by a very low density hollow in the cloud. Matter falling in from the cloud towards the star is the raw material for the formation of planets and satellites.The study of the evolution of a dark cloud leads to a scenario of planet formation which is reconcilable with the results obtained from studies based on solar system data. This means that the new approach to cosmical plasma physics discussed in Part I logically leads to a consistent picture of the evolution of dark clouds and the formation of solar systems. 相似文献
12.
J. F. Valdés-Galicia G. Wibberenz J. J. Quenby X. Moussas G. Green F. M. Neubauer 《Solar physics》1988,117(1):135-156
In the quasi-linear theory of pitch angle scattering the power spectrum of magnetic field fluctuations is related to the shape of the pitch angle diffusion coefficient D(), the absolute value of the mean free path , and the rigidity dependence of the mean free path (R). We discuss these relations in detail during the solar particle event of 11 April, 1978 which was observed on HELIOS-2 at a distance of 0.49 AU from the Sun. Magnetic field measurements obtained during the time of the event are used as a basis for the layer model in which the method of particle trajectories in an actually measured field is used to simulate pitch angle diffusion. The values of D() and based on the trajectory simulation for 100 MeV protons (field approach) are compared with results obtained from solar proton data (particle approach) and with predictions from quasi-linear theory based on the additional assumption of the slab model for magnetic field fluctuations (QLT approach). The time of the event is characterized by a high level of field fluctuations, the observed mean free path of about 0.03 AU for 100 MeV protons is smaller than the average value near 1 AU. Results from the field and particle approaches agree surprisingly well. The remaining difference in the mean free path of about a factor of 2 could be due to tangential discontinuities which are measured by the magnetometer, but not seen by the real particles traveling along the average field. The results from the field and QLT approaches based on the same set of magnetic field measurements differ by about a factor of 4. One of the reasons for this discrepancy is that the conditions for resonance scattering are only marginally valid. In addition, the wave vectors representing Alfvén-type fluctuations may not be totally field aligned. This deviation from the slab model would cause an increase of the theoretically predicted mean free path and lead to better agreement with the other two approaches. 相似文献
13.
Robert M. Wilson 《Solar physics》1986,106(1):29-33
Mt. Wilson numbers of spots data (as defined in Howard et al., 1984) appear to be distributed according to even-odd cycle numbering. Linear fits of annual numbers of spots versus annual sunspot number for even- and odd-numbered cycles have slopes which are statistically different at the 5% level of significance. The existence of an even-odd split in Mt. Wilson numbers of spots data may be due either to a real difference in even- and odd-numbered cycles on the Sun or to a difference in weather at Mt. Wilson (perhaps, related to the 22-yr rhythm of drought in the western United States) during even- and odd-numbered cycles, or both. For cycle 22, an even-numbered cycle, the peak numbers of spots is estimated to be near 2600. 相似文献
14.
We implement a complex-plane strategy and a multiple partition technique to the computation of polytropic models distorted by very strong and very rapid differential rotation. We also verify with our numerical results a heuristic relation between stability and virial theorem. 相似文献
15.
. , , . , t>1010 ( z<105) .
In this paper we continue the work of Weymann, investigating the causes of distortion of the spectrum of the residual radiation from the Planck curve. We discuss the distortion to the spectrum, resulting from recombination of primeval plasma.We then derive an analytic expression for the distortion to the equilibrium spectrum due to Compton scattering by hot electrons. On the basis of the observational data we conclude that a period of the existence of neutral hydrogen is inescapable in the hot model of the universe. It is concluded that any injection of energy att>1010 sec (red shiftz<105) give the distortions of the equilibrium spectrum.相似文献
16.
K. V. K. Iyengar 《Astrophysics and Space Science》1986,122(2):257-262
A search (using the Infrared Astronomical Satellite IRAS point source catalogue) for infrared counterparts of the fourteen new candidates for planetary nebulae of low surface brightness detected by Hartl and Tritton (1985), resulted in only five identifications. The infrared sources of four of these candidate nebulae are found within 5 are sec of their optical position and the fifth one within 1 are min. Two of the five nebulae identified with infrared sources are classified as true, one as probable and two as possible by Hartl and Tritton (1985). All the five nebulae are found in regions of high cirrus flux at 100 m. These nebulae are all found to have both point sources as well as small size extended sources (in the IRAS scan windows centred on the sources), with numbers varying from field to field. The infrared emission from these nebulae have dust temperatures 100K (characteristic of planetary nebulae). Four of the nebulae appear to be faint in the infrared (just as in the optical band) with total infrared flux of 2×10–13 W m–2. Only the PN candidate No. 12 appears to be very bright in the infrared. It is likely that part of the emission is from extraneous sources in the line-of-sight to the nebula. 相似文献
17.
Yngve Öhman 《Solar physics》1985,96(1):209-212
It is suggested, that effects of total reflection and refraction may appear sometimes in various objects on the Sun in connection with grazing incidence towards layers formed by magnetic fields and perhaps also by electrostatic double layers or shock waves. It seems possible that such effects may influence sometimes the contrast of bright structures as well as dark structures at selective wavelengths as well as in white light. 相似文献
18.
The problem of stability of an unbounded anisotropic plasma characterized by different temperatures along and transverse to the magnetic field is investigated for an arbitrary direction of propagation. Chewet al (1956) equations modified to incorporate self-gravitation, finite ion Larmor radius (FLR) and Hall current are used. Uniform rotation (of an order of interest in astrophysics) is also considered. Extensive numerical treatment of the dispersion relation leads to several interesting results.Inclusion of FLR, or Hall current or both together introduces pulsational instability for prepagation parallel to the magnetic field. The aperiodic growth rate of the mirror instability is only slightly altered due to FLR or Hall current effects. In the absence of rotation, self-gravitation, FLR and Hall current, the growth rate decreases for the mirror region as the direction of propagation approaches the field direction, while the fire hose instability persists for arbitrary propagation, even in the limiting case (the mirror limit) where the propagation is nearly transverse to the magnetic field. Uniform rotation altogether stabilizes the fire hose instability for a sufficiently strong pressure (or temperature) anisotropy. Pulsational instability is introduced when both ratation and self-gravitation effects are present. Either FLR or Hall current depresses the growth rate of the fire hose instability and introduces pulsational instability for the general case of arbitrary propagation. When FLR and Hall current effects are present simultaneously, the interaction terms due to these effects may be strongly destabilizing in nature for arbitrary propagation. 相似文献
19.
E. Budding 《Astrophysics and Space Science》1974,29(1):17-39
The proximity effects in the light curves of close binary systems are investigated with the aid of facilities provided by a high-speed, digital computer. The treatment follows, to a large extent, that summarized by Kopal (1959) and makes extensive use of the alpha-functions and related integrals provided by that author. The ellipticity and reflection effects are studied individually and different expressions are checked and compared. Test data are drawn continually from the well known system SZ Cam for which a rectified (in a more realistic sense) light curve is ultimately produced. 相似文献
20.
G. A. Krasinsky 《Celestial Mechanics and Dynamical Astronomy》1972,6(1):60-83
The general conception of the critical inclinations and eccentricities for theN-planet problem is introduced. The connection of this conception with the existence and stability of particular solutions is established. In the restricted circular problem of three bodies the existence of the critical inclinations is proved for any values of the ratio of semiaxes . The asymptotic behaviour of the critical inclinations as 1 is investigated.
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