共查询到20条相似文献，搜索用时 31 毫秒
1.
The force-free electromagnetic field represents a natural generalization of the well-known force-free magnetic field model and allows the magnetic field to maintain electric charge separation.The basic equation for the cylindrical oscillations of the force-free electromagnetic field is obtained and solved for a linear case. The spectrum of possible resonances in a magnetized atmosphere is discussed. 相似文献
2.
Rotational perturbations of charged cosmological viscous-fluid universes coupled with a scalar field
Manihar Singh Koijam 《Astrophysics and Space Science》1989,162(1):129-150
The dynamics of a slowly rotating charged viscous-fluid Universe coupled with a zero-mass scalar field is investigated; and the rotational perturbations of such models are studied in order to substantiate the possibility that the Universe is endowed with slow rotation, in the course of presentation of several new analytic solutions. The effects of charged field and scalar field on the rotational motion are discussed. Except for perfect dragging, the scalar field as well as the charged field is found to have a damping effect on the rotation of matter. Rotating models which are expanding as well are obtained, in which cases the rotational velocities are found to decay with the time, and these models may be taken as good examples of real astrophysical situations. The periods of physical validity of different models are also obtained. 相似文献
3.
Relativistic cosmological field equations are obtained for a Robertson-Walker space time interacting with viscous fluid and
massive scalar field. The cosmological solutions to the field equations are obtained and the nature of the scalar field as
well as the viscous fluid are studied. It is found that the solutions obtained are realistic only for a closed Universe.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
H. M. Antia 《Journal of Astrophysics and Astronomy》2008,29(1-2):85-92
Magnetic field in the solar interior contributes to the even order splitting coefficients, but it is not possible to separate the effect of magnetic field from those due to other deviations from spherical symmetry. Results obtained using GONG and MDI data are discussed. Limits on possible magnetic field in the solar core and in the tachocline region are obtained. There is some signal from possible magnetic field in the convection zone, but evidence of possible temporal variation in the solar interior is only marginal. 相似文献
5.
The field equations of the New General Relativity NGR, constructed by Hayashi and Shirafuji (1979), have been applied to two geometric structures, given by Robertson (1932), in the domain of cosmology. In the first application a family of models, involving two of the parameters characterizing the field equations of the NGR, is obtained. In the second application the models obtained are found to involve one parameter only. The cosmological parameters in both applications are calculated and some cosmological problems are discussed in comparison with the corresponding results of other field theories . 相似文献
6.
The paper discusses the possibilty of interpreting the magnetic fields of astronomical bodies in the framework of a unified field theory.Using one of the solutions of the generalized field theory, a direct relation between the polar magnetic field, the angular velocity and the gravitational potential of the body considered, is obtained. The geometric model used for applications has spherical symmetry and is of the type (FIGI).The predictions of the theoretical formula, obtained from the model, are compared with available observational data, and with the empirical formula of Blackett. The theoretical formula gives a possible interpretation of a seed magnetic field which will develop and produce the large-scale magnetic field observed for celestial objects. The formula shows that the field is generated as a result of rotation of a massive object. 相似文献
7.
I. A. Yakunin 《Astrophysical Bulletin》2013,68(2):214-218
Based on the spectropolarimetric data obtained at the 6-m telescope, a study of the magnetic field and physical parameters of the magnetic He-weak star HD 35298 was performed. A comparison of the results of magnetic field measurements by various methods has been carried out. The star’s magnetic field varies in the range from ?3 to +3 kG. The field geometry is explained in terms of the oblique rotator model. The obtained magnetic field variation curve can be described by a central dipole with the dipole axis inclined to the axis of rotation by β = 60°, and the magnetic field strength at the pole of B p = 11.5 kG. The data on the variability of spectral lines of some metals are presented, allowing to make an assumption that the stellar surface is heavily spotted. 相似文献
8.
We have studied an electron-photon cascade in an isotropic photon field as one of the possible gamma-ray generation mechanisms in compact sources.A cascade in a monoenergetic photon field and in a field of the power-law spectrum is considered. Two types of interaction of cascade particles with the photon field are taken into account: the inverse Compton scattering of electrons and the photoproduction of electron-positron pairs by gamma-quanta. The cascade characteristics have been obtained by numerical solution of the kinetic equations. A quantitative and qualitative analysis is made of the main regularities of the cascade. We have established simple relations between the spectra of cascade particles and the parameters of the photon field and primary radiation. The magnetic field effect on the cascade characteristics is estimated. The results obtained are compared with the results of calculation of other investigators.In the first part of the paper we outline the method of solution and the results relating to the monoenergetic photon field. The theory of cascades in a photon field of the power-law spectrum and its application to the problem of gamma-rays in compact sources are discussed in the second part of the present paper. 相似文献
9.
F.Z. Feygin A.L. Kalisher V.A. Pilipenko O.A. Pokhotelov K. Dobeś 《Planetary and Space Science》1979,27(7):913-923
The stability of the hot plasma located at the curvilinear geomagnetic field in relation to the generation of Alfvén oscillations is investigated. A general expression for the increment is obtained. The increments for the short wavelength disturbances and special energy distribution function in a parabolic magnetic field are presented. The obtained theoretical results are used in interpreting the oscillations of the “auroral radiation” type. The polarization relations in Alfvén waves are investigated. 相似文献
10.
Consideration is given to the motion of electrons in a photon field of the monoenergetic or power-law spectrum under the conditions when the main mechanism of energy loss is the inverse Compton scattering by field photons. This process changes the primary spectrum of electrons and converts low-energy field photons to high-energy gamma-quanta for which the electron confinement region is assumed to be optically thin. The electron and gamma-ray spectra have been obtained in a wide energy interval including the Klein-Nishina and Thomson regions. A simple qualitative dependence of the solutions found on the field parameters and the primary spectrum of electrons has been established.The electron and gamma-ray spectra have been obtained by numerically solving the kinetic equation dependent on two variables: the energy of electrons and their path (or the time of motion) in a photon field. The results dramatically differ from the solution of the steady-state kinetic equation which depends only on the electron energy and is frequently used in the given problem. 相似文献
11.
The effect of rotation on the self-gravitational instability of an infinite homogeneous magnetised gas-particle medium in the presence of suspended particles is investigated. The conductivity of the medium is assumed to be finite. The equations of the problem are linearized and the general dispersion relation is obtained. The rotation is assumed along two different directions separately and separate dispersion relation for each case is obtained. The dispersion relation for propagation parallel and perpendicular to the uniform magnetic field along with rotation is derived. It is found that in presence of suspended particles, magnetic field, finite conductivity, rotation and viscosity, Jeans's criterion determines the condition of gravitational instability of gas-particle medium. 相似文献
12.
The stability problem in cosmology is studied using the equations of geodesic deviation. General conditions for stability are obtained. The method is applied to a number of cosmological models, resulting from different field theories. The results are compared with those obtained from FRW-models. 相似文献
13.
The aim of the present paper is to investigate the influence both of intitial stress and magnetic field on the propagation of Rayleigh waves in thermo-microelastic half-space subjected to certain boundary conditions. The wave velocity equation has been obtained. If the initial stress and the electromagnetic field are ignored, the frequency equation as obtained by Locket (1958). 相似文献
14.
Thermal-convective-instability of a stellar atmosphere in the presence of a nonlinear magnetic field
A. A. Abdullah 《Astrophysics and Space Science》1992,196(1):109-115
Thermal-convective-instability of a stellar atmosphere is investigated in the presences of a nonlinear magnetic field. A model proposed by Roberts (1981) in the context of neutron stars is used. The simultaneous effect of both nonlinear magnetic field and rotation is also considered. The criteria obtained for monotonic instability generalize the criterion derived by Defouw (1970) in the absence of magnetic field and rotation. 相似文献
15.
Qing-rui Su 《Chinese Astronomy and Astrophysics》1985,9(2):170-174
The corresponding field configurations of the solar isothermal atmosphere obtained from a series of non-constant shearing magnetic fields after considering both the gravity and gas pressure are examined and compared. When the shearing magnetic field increases, magnetic islands will appear, followed by shearing, quasi-three-dimensional field structures approaching the open state and with almost anti-parallel field lines. It is possible that this is related to the initial phase of a two ribbon flare. 相似文献
16.
The polarity of the interplanetary magnetic field observed by the Mariner IV spacecraft is compared to the polarity of the photospheric magnetic field observed with the solar magnetograph at Mt. Wilson Observatory. Unlike the results obtained from observations during the flight of IMP-I, these polarities are not well correlated when the photospheric polarity is determined from data along a narrow latitudinal strip. It is suggested that the structure of the interplanetary field is often related to major features in the photospheric field that are observed over a broad range of solar latitudes. 相似文献
17.
The features of the relativistic charge particle motion and emission due to the radiative slamping in the strong electromagnetic fields are investigated. It is shown that the radiative force responsible for curvature radiation is associated with the particle drift in an inhomogeneous magnetic field. The adiabatic trajectory is obtained for the relativistic particle, moving in a strong static electron-magnetic field, particle energy being determined by the balance of the work of the electric field and the energy losses through curvature radiation. 相似文献
18.
Mitsugu Makita 《Solar physics》1986,103(1):1-10
The Faraday rotation in the sunspot atmosphere is statistically detected by examining directions of the linear polarization obtained with the vector magnetograph of the Okayama Astrophysical Observatory. It is very effective near the spectral line center and the azimuth of the linear polarization deviates greatly from the magnetic field azimuth. In the case of the iron line, 5250 Å, the magnetic field azimuth will be obtained with an accuracy better than 15°, if observed in the line wing from 27 to 80 mÅ relative to the line center. 相似文献
19.
The propagation of sonic discontinuity in conducting and radiating atmosphere has been discussed under the influence of magnetic field. The velocity of sonic wave and its termination into shock wave has been obtained. We have also obtained the critical time at which sonic wave terminates into shock wave. There is significant effect of magnetic field on sonic velocity and its termination into shock wave. 相似文献
20.
Daniel Atnafu Chekole Gebretsadikan Woldmhret Bahta 《Journal of Astrophysics and Astronomy》2018,39(6):67
Magnetohydrodynamics waves and instabilities in rotating, self-gravitating, anisotropic and collision-less plasma were investigated. The general dispersion relation was obtained using standard mode analysis by constructing the linearized set of equations. The wave mode solutions and stability properties of the dispersion relations are discussed in the propagations transverse and parallel to the magnetic field. These special cases are discussed considering the axis of rotation to be in transverse and along the magnetic field. In the case of propagation transverse to the magnetic field with axis of rotation parallel to the magnetic field, we derived the dispersion relation modified by rotation and self-gravitation. In the case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we obtained two separate modes affected by rotation and self-gravitation. This indicates that the Slow mode and fire hose instability are not affected by rotation. Numerical analysis was performed for oblique propagation to show the effect of rotation and self-gravitation. It is found that rotation has an effect of reducing the value of the phase speeds on the fast and Alfven wave modes, but self-gravitation affect only on the Slow modes, thereby reducing the phase speed compare to the ideal magneto hydrodynamic (MHD) case. 相似文献