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1.
The propagation of axially symmetric wave beams near the equatorial plane of a neutron star is studied. These waves are excited by a spatially bounded perturbation in the form of a transverse magnetic field applied to the inner boundary of the crust of the star. For a small ratio of the perturbed to the unperturbed magnetic field, a linear theory can be employed to solve the evolution equation. This condition is satisfied in the crust plasma of a neutron star for typical radio luminosities of pulsars. The resulting simple, exact solution in the form of linear gaussian beams exists without additional conditions on the dissipation, dispersion, and narrowness of the beams, if the velocity c
n of these waves is constant. The latter requirement is well satisfied for the plasma in neutron star crusts. The width of the gaussian beam also depends weakly on position. 相似文献
2.
The propagation of axisymmetric magnetohydrodynamic waves near the equatorial plane of the crust of a neutron star that is in a transverse magnetic field is considered. These waves are excited by a spatially limited excitation in the form of a transverse magnetic field applied to the inner boundary of the neutron star's crust. The magnetic fields and electric currents excited at the stellar surface by this wave beam are determined. 相似文献
3.
The propagation of axisymmetric magnetohydrodynamic waves near the equatorial plane of the crust of a neutron star in a transverse magnetic field is considered. The magnetic field is perpendicular to the equatorial plane. The magnetic fields and electric currents excited by this wave beam at the stellar surface are determined. 相似文献
4.
Equilibrium configuration of the magnetosphere of a star loaded by the gravitationally accreted plasma having its own magnetic
field is investigated. Axisymmetry around the star’s magnetic axis is assumed for simplicity. It is seen that two distinct
configurations appear for the cases of parallel and antiparallel magnetic field of the accreted plasma with respect to the
star’s magnetic moment. If the external field is antiparallel to the star’s magnetic moment, the stellar magnetosphere is
confined within a spherical region surrounded by the external field with a separatric surface between them. This is an extension
of the case of the spherical accretion of non-magnetic plasma dealt with thus far in connection with the mass accretion by
the degenerate stars in X-ray binaries. It is noticed that the mass slides down along the field lines to the point closest
to the star and is stratified hydrostatically in equilibrium to form a disk in the equatorial plane. The mass loading compresses
the sphere as a whole in this case. If, on the other hand, the external field is parallel to the star’s magnetic moment, there
appears a ring of magnetic neutral point in the equatorial plane. Polar field is open and extends to infinity while the low-latitude
field is closed and faces the external field of opposite polarity across the neutral point. The increase of the loaded mass
in this case causes a shrink of the closed field region, and the open polar flux is increased. Therefore, the transition between
equilibria with small and large amount of the loaded mass requires the reconnection of magnetic lines of force, and the reconnection
of the flux through the magnetic neutral ring is proposed as the mechanism of the steady or the intermittent mass leakage
like the ones postulated for some X-ray bursters.
Visiting Scientist supported by the Japan Society for the Promotion of Sciences. 相似文献
5.
G. S. Sahakian 《Astrophysics》2000,43(1):111-126
The theory of pulsar radio emission has been developed in a series of our papers since 1992. It was shown that pulsar radio
emission is produced in the lower part of a channel of open magnetic field lines, in a region with a height h ≈ 1.1-107 μ
30
1/3
/P4/21 cm above a magnetic cap of the neutron star (P is the pulsar’s period and μ is the star’s magnetic moment). Here, owing to
vigorously occurring processes (the production of photons of curvature radiation and their annihilation into e+e- pairs), two ultrarelativistic particle fluxes are formed: an electron flux moving upward and a positron flux falling onto
the star’s magnetic cap. These main fluxes are accompanied by narrow strips of positron and electron fluxes of relatively
low energy, the curvature emission from which is a strong coherent radio source. The present paper is a review of earlier
papers, and important additions and refinements are also made. Equations are offered for the radio luminosity of a pulsar,
the solid angle of the radio beam, and the magnetic moment and moment of inertia of the pulsar’s neutron star.
Translated from Astrofizika, Vol. 43, No. 1, pp. 147-169, January–March, 2000. 相似文献
6.
D. M. Sedrakian 《Astrophysics》2000,43(3):275-281
The influence of the effect of entrainment of superconducting protons by superfluid neutrons on the distribution of neutron
vortices in a rotating neutron star is investigated. It is shown that the proton vortex clusters generated by entrainment
currents create the magnetic structure of a neutron vortex. The average magnetic field induction in a neutron vortex is calculated.
The presence of the magnetic field of a neutron vortex considerably alters the radius of the vortex zone. The width of the
vortex-free zone at the surface of the neutron star’s core increases, reaching macroscopic values on the order of several
meters. This result considerably changes earlier concepts of the distribution of neutron vortices in a neutron star.
Translated from Astrofizika, Vol. 43, No. 3, pp. 377-386, July–September, 2000. 相似文献
7.
Preliminary data on the magnetic field structure of the unique magnetic star HD 45583 are obtained. The observational data
are well described by a configuration of two magnetic dipoles located on opposite sides relative to the star’s center, with
their axes directed roughly in a radial direction. The positive monopoles are closer to the surface and the negative, closer
to the star’s center. For this reason, there appear to be two positive magnetic poles on the star’s surface but no negative
poles. The need for further observations of this unique object is pointed out.
Translated from Astrofizika, Vol. 52, No. 1, pp. 127–133 (February 2009). 相似文献
8.
Malvin Ruderman 《Journal of Astrophysics and Astronomy》1995,16(2):207-216
Interactions among a neutron star’s superfluid neutrons, superconducting protons, and solid crust cause predictable spin-down
and spin-up driven crustal motion and magnetic field changes. Applications and unsolved problems are discussed for millisecond
pulsar evolution and properties, glitches and post-glitch responses, and transcient gamma-ray emission. 相似文献
9.
The magneto-rotational evolution of a neutron star in the massive binary system 4U 2206+54 is discussed in light of the recent
discovery of its 5555 s rotational period and its average rate of spin-down. We show that this behavior of the neutron star
means that its magnetic field exceeds the quantum mechanical critical limit and it is an accretion magnetar. The system’s
evolution is explained by wind driven mass transfer without formation of an accretion disk. The constant character of the
x-ray source indicates a steady rate of accretion and raises anew the question of the stability of the boundary of the magnetosphere
of a star undergoing spherical accretion. A solution to this problem is also a key to determining the mechanism for the slowing
down of the star’s rotation. 相似文献
10.
Kostas Glampedakis Lars Samuelsson Nils Andersson 《Astrophysics and Space Science》2007,308(1-4):607-611
The presence of a magnetic field in a neutron star interior results in a dynamical coupling between the fluid core and the
elastic crust. We consider a simple toy-model where this coupling is taken into account and compute the system’s mode oscillations.
Our results suggest that the notion of pure torsional crust modes is not useful for the coupled system, instead all modes
excite Alfvén waves in the core. However, we also show that among a rich spectrum of global MHD modes the ones most likely
to be excited by a fractured crust are those for which the crust and the core oscillate in concert. For our simple model,
the frequencies of these modes are similar to the “pure crustal” frequencies. We advocate the significant implications of
these results for the attempted theoretical interpretation of QPOs during magnetar flares in terms of neutron star oscillations.
相似文献
11.
Robert C. Fleck 《Astrophysics and Space Science》2008,313(4):351-356
A magnetic torque associated with the magnetic field linking a giant, gaseous protoplanet to its host pre-main-sequence star
can halt inward protoplanet migration. This torque results from a toroidal magnetic field generated from the star’s poloidal
(dipole) field by the twisting differential motion between the star’s rotation and the protoplanet’s revolution. Outside the
corotation radius, where a protoplanet orbits slower than its host star spins, this torque transfers angular momentum from
the star to the protoplanet, halting inward migration. Necessary conditions for angular momentum transfer include the requirement
that the Alfvén speed v
A
in the region magnetically linking a protoplanet to its host star exceeds the protoplanet’s orbital speed v
K
. In addition, the timescale for Ohmic dissipation τ
D
must exceed the protoplanet’s orbital period P to ensure that the protoplanet is magnetically coupled to its host star. For a Jupiter-mass protoplanet orbiting a solar-mass
pre-main-sequence star, v
A
>v
K
and τ
D
>P only when the migrating protoplanet approaches within about 0.1 AU of its host star, primarily because of the rapid drop
in the strength of the magnetic field with increasing distance from the central star. Because of this restricted reach, inwardly
migrating gaseous protoplanets can be expected to “pile up” very close to their central stars, as is indeed observed for extrasolar
planets. The characteristic timescale required for a magnetic torque to transfer angular momentum outward from a more rapidly
spinning central star to a magnetically coupled protoplanet is found to be comparable to planet-forming disk lifetimes and
protoplanet migration timescales. 相似文献
12.
Energy release in the superconducting core of a neutron star as neutron vortices move toward the boundary of the star’s core
and crust is examined. It is shown that the rate of energy release is on the order of 1026-1030 erg/s, or sufficient to provide the radio luminosity of known pulsars. The energy release rates calculated under the assumption
of asymmetric energy release are compared with observational data on the radio luminosity of 575 pulsars. 相似文献
13.
The forces acting on the solid crust of a differentially rotating neutron star are examined when a nonuniform excess of chemical
potential exists. The resultant of the external forces, a stress force, is expressed in terms of a centrifugal buoyancy force
and the deformation of the star’s crust under the action of this force is calculated. It is shown that there is a region within
the star where the resulting stresses lead to fracture of the crust when the difference in the angular velocities of the superfluid
and normal components reaches a critical value. The “centrifugal buoyancy” mechanism for generating a glitch is used to estimate
the parameters of glitches in the Vela pulsar.
__________
Translated from Astrofizika, Vol. 50, No. 2, pp. 183–197 (May 2007). 相似文献
14.
Yu. V. Glagolevskij 《Astrophysics》2010,53(4):536-543
Models of the magnetic field of the He-w star HD142301 are constructed. Observational data are well described by the model
of a dipole shifted by 0.6 stellar radii transverse to the axis. The phase dependence of the HeI λ4026? line, however, corresponds
better to a model assuming the presence of four monopoles (or two dipoles) shifted by 0.4 stellar radii from the center. The
distance between the monopoles in both models is comparable to the star’s radius, which indicates that the source of the magnetic
field is “long” dipoles, rather than “point” dipoles. 相似文献
15.
Bahodir B. Ahmedov 《Astrophysics and Space Science》2011,331(2):565-573
The general-relativistic Ohm’s law for a two-component plasma which includes the gravitomagnetic force terms even in the case
of quasi-neutrality has been derived. The equations that describe the electromagnetic processes in a plasma surrounding a
neutron star are obtained by using the general relativistic form of Maxwell equations in a geometry of slow rotating gravitational
object. In addition to the general-relativistic effect first discussed by Khanna and Camenzind (Astron. Astrophys. 307:665,
1996) we predict a mechanism of the generation of azimuthal current under the general relativistic effect of dragging of inertial
frames on radial current in a plasma around neutron star. The azimuthal current being proportional to the angular velocity
ω of the dragging of inertial frames can give valuable contribution on the evolution of the stellar magnetic field if ω exceeds 2.7×1017(n/σ) s−1 (n is the number density of the charged particles, σ is the conductivity of plasma). Thus in general relativity a rotating neutron star, embedded in plasma, can in principle
generate axial-symmetric magnetic fields even in axisymmetry. However, classical Cowling’s antidynamo theorem, according to
which a stationary axial-symmetric magnetic field can not be sustained against ohmic diffusion, has to be hold in the general-relativistic
case for the typical plasma being responsible for the rotating neutron star. 相似文献
16.
S. I. Bastrukov H.-K. Chang I. V. Molodtsova E.-H. Wu G.-T. Chen S.-H. Lan 《Astrophysics and Space Science》2009,323(3):235-242
Using the energy variational method of magneto-solid-mechanical theory of a perfectly conducting elastic medium threaded by
magnetic field, the frequency spectrum of Lorentz-force-driven global torsional nodeless vibrations of a neutron star with
Ferraro’s form of axisymmetric poloidal nonhomogeneous internal and dipole-like external magnetic field is obtained and compared
with that for this toroidal Alfvén mode in a neutron star with homogeneous internal and dipolar external magnetic field. The
relevance of considered asteroseismic models to quasi-periodic oscillations of the X-ray flux during the ultra powerful outbursts
of SGR 1806−20 and SGR 1900+14 is discussed. 相似文献
17.
RX J1856.5-3754 has been proposed as a strange star candidate due to its very small apparent radius measured from its X-ray
thermal spectrum. However, its optical emission requires a much larger radius and thus most of the stellar surface must be
cold and undetectable in X-rays. In the case the star is a neutron star such a surface temperature distribution can be explained
by the presence of a strong toroidal field in the crust (Pérez-Azorín et al.: Astron. Astrophys. 451, 1009 (2006); Geppert
et al.: Astron. Astrophys. 457, 937 (2006)) We consider a similar scenario for a strange star with a thin baryonic crust to
determine if such a magnetic field induced effect is still possible.
This work was partially supported by PAPIIT, UNAM, grant IN119306. J.A.H. studies at UNAM and travel to London are covered
by fellowships from UNAM’s Dirección General de Estudios de Posgrado. 相似文献
18.
A model is constructed for the magnetic field of the He-weak CP star HD 21699. This star has the field structure of a dipole
displaced by 0.4 radii from the center perpendicular to its axis. The magnetic poles appear to be close to one another on
the surface; they are separated by 55°, not by 180° as in the case of a central dipole. The phase dependences of the equivalent
widths of He and Si lines have extrema at the phases corresponding to passage through the visible meridian of zero magnetic
field between the magnetic poles. At the magnetic poles, the intensity of the helium lines is maximal and of the silicon lines,
minimal. The silicon abundance is maximal in the regions where the magnetic field is predominantly tangential to the star’s
surface. Because of averaging over the visible hemisphere and owing to the closeness of the magnetic poles, only one wave
of variation in the intensity of the spectral lines of these chemical elements, one wave of photometric variability, and an
average surface magnetic field Bs are observed.
__________
Translated from Astrofizika, Vol. 50, No. 3, pp. 441–451 (August 2007). 相似文献
19.
Natural, low-frequency, hydromagnetic oscillations of an isolated, nonrotating neutron star, which are localized in the peripheral
crust, the structure of which is determined by the electron-nuclear plasma (the Ae phase), are studied. The plasma medium
of the outer crust is treated as a homogeneous, infinitely conducting, incompressible continuum, the motions of which are
determined by the equations of magnetohydrodynamics. In the approximation of a constant magnetic field inside the crust (the
magnetic field outside the star is assumed to have a dipole structure), the spectrum of normal poloidal and toroidal hydromagnetic
oscillations, due to presumed residual fluctuations of flow and their associated fluctuations in magnetic field strength,
is calculated. Numerical estimates given for the periods of MHD oscillations fall in the range of periods of radio pulsar
emission, indicating a close connection between the residual hydromagnetic oscillations and the electromagnetic activity of
neutron stars.
Translated from Astrofizika, Vol. 40, No. 1, pp. 77–86, January–March, 1997. 相似文献
20.
Quasi-simultaneous photoelectric and spectroscopic observations of the active spotted star V 775 Her have been made for the
first time and showed an increase in the equivalent width of the pure emission in the Ha line with a decrease in the star’s brightness. Such an increase was due to an increase in electron density in the active
regions and demonstrates a connection between active regions and cool spots. The system’s photometric variability is fully
described within the framework of a zonal model. The spotted regions occupy up to 42% of the star’s total surface if the temperature
difference between the quiet photosphere and a spot is about 900 K. The ratio of the masses of the components of V 775 Her
is estimated for the first time.
Translated from Astrofizika, Vol. 43, No. 3, pp. 339-351, July–September, 2000. 相似文献