共查询到20条相似文献,搜索用时 15 毫秒
1.
Ahmadjon Abdujabbarov Farruh Atamurotov Yusuf Kucukakca Bobomurat Ahmedov Ugur Camci 《Astrophysics and Space Science》2013,344(2):429-435
The shadow of a rotating black hole with nonvanishing gravitomagnetic charge has been studied. It was shown that in addition to the angular momentum of black hole the gravitomagnetic charge term deforms the shape of the black hole shadow. From the numerical results we have obtained that for a given value of the rotation parameter, the presence of a gravitomagnetic charge enlarges the shadow and reduces its deformation with respect to the spacetime without gravitomagnetic charge. Finally we have studied the capture cross section for massive particles by black hole with the nonvanishing gravitomagnetic charge. 相似文献
2.
Mohsen Shadmehri 《Astrophysics and Space Science》2008,314(1-3):217-223
We study the effect of an imposed magnetic field on the motion of charged dust particles in magnetically active regions of
a protoplanetary disc. Assuming a power law structure for the vertical and the toroidal components of the magnetic field for
the regions beyond magnetically dead region of the disc, the radial and the vertical velocities of the charged particles,
in the asymptotic case of small particles, are calculated analytically. While grains with radii smaller than a critical radius
significantly are affected by the magnetic force, motion of the particles with larger radii is independent of the magnetic
field. The critical radius depends on the magnetic geometry and the charge of the grains. Assuming that a grain particle has
one elementary charge and the physical properties of the disc correspond to a minimum-mass solar nebula, we show that only
micron-sized grains are affected by the magnetic force. Also, charge polarity determines direction of the radial velocity.
For such small particles, both the radial and the vertical velocities increase due to the magnetic force. 相似文献
3.
S. K. El-Labany E. F. El-Shamy R. Sabry M. Shokry 《Astrophysics and Space Science》2010,325(2):201-207
In the present paper, the characteristics of the head-on collision between two dust-acoustic solitary waves (DASWs) in an
adiabatic dusty plasma consisting of variable negatively charged dust grains, isothermal electrons and two-temperature isothermal
ions in the presence of an external oblique magnetic field are investigated. Using the extended Poincaré–Lighthill–Kuo (PLK)
method, the Korteweg–de Vries (KdV) equations and the analytical phase shifts after the head-on collision of two solitary
waves are derived. The effects of the magnetic field and its obliqueness, two different type of isothermal ions and the dust
particles adiabaticity are discussed. It is found that these factors significantly affect the phase shifts. 相似文献
4.
Kouichi Hirotani 《Astrophysics and Space Science》2005,297(1-4):81-91
We investigate a stationary pair production cascade in the outer magnetosphere of an isolated, spinning neutron star. The
charge depletion due to global flows of charged particles, causes a large electric field along the magnetic field lines. Migratory
electrons and/or positrons are accelerated by this field to radiate gamma-rays via curvature and inverse-Compton processes.
Some of such gamma-rays collide with the X-rays to materialize as pairs in the gap. The replenished charges partially screen
the electric field, which is self-consistently solved together with the energy distribution of particles and gamma-rays at
each point along the field lines. By solving the set of Maxwell and Boltzmann equations, we demonstrate that an external injection
of charged particles at nearly Goldreich-Julian rate does not quench the gap but shifts its position and that the particle
energy distribution cannot be described by a power-law. The injected particles are accelerated in the gap and escape from
it with large Lorentz factors. We show that such escaping particles migrating outside of the gap contribute significantly
to the gamma-ray luminosity for young pulsars and that the soft gamma-ray spectrum between 100 MeV and 3 GeV observed for
the Vela pulsar can be explained by this component. We also discuss that the luminosity of the gamma-rays emitted by the escaping
particles is naturally proportional to the square root of the spin-down luminosity. 相似文献
5.
Energetic charged particles, which are often observed in solar active regions, may be also produced in interplanetary space due to the decoupling of ions and electrons in plasma. The Hall term in general Ohm's law is generally thought to be responsible for the decoupling of electrons and ions in plasma during magnetic reconnection. In this paper, a Hall MHD model is developed to study energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity. Two energetic charged particle events are used to test this model. It is concluded that the Hall effect does not only play the important role in the process of magnetic reconnection, but also in energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity. 相似文献
6.
The propagation of energetic particles in the interplanetary space is considered on the basis of kinetic equation describing
the scattering of charged particles by magnetic irregularities and the particle focusing by regular magnetic field. Our analysis
confirms that angular distribution of solar cosmic rays contains a valuable information about properties of the particle scattering
in the interplanetary magnetic field. Steady state solutions of the kinetic equation are applied to the analysis of solar
proton events. 相似文献
7.
S. Simons 《Astrophysics and Space Science》1976,41(2):423-434
The results of the preceding paper are applied to a consideration of the motion of grains in a magnetic field, the calculation of particle collision cross-sections and charge effects in molecular synthesis. 相似文献
8.
L. I. Dorman M. E. Katz Yu. I. Fedorov B. A. Shakhov 《Astrophysics and Space Science》1983,94(1):43-95
A consistent theory of energy exchange between high-energy charged cosmic-ray particles and the random inhomogeneities of a magnetic field frozen in the moving solar wind plasma is developed. It is shown that the mode of the particle energy variations at a given law of plasma velocity variation in space is determined by the specific form of the particle distribution function. The equation for the density of cosmic-ray energy is obtained. Consideration is given to the generation of a charged particle energy spectrum in the course of multiple scatterings by the random inhomogeneities of the magnetic field. 相似文献
9.
The model of a black hole rotating in an external magnetic field is considered. The mechanisms of the energy extraction from the black hole in terms of the effective ergospheres for charged particles are described. It is shown that the external magnetic field essentially influences the boundaries of the effective ergospheres and the superradiance threshold. 相似文献
10.
Yu. A. Rylov 《Astrophysics and Space Science》1977,51(1):59-75
Numerical calculations of the electron cap shape of a rapidly rotating neutron star with a strong magnetic field have been provided. It is supposed that the magnetic dipole axis is aligned, and ejection of positive charged particles from the star's surface absent. The total charge of the star has been calculated. Estimation of the character of charged-particle motion in the electromagnetic field of the star has been obtained. It is shown that two streams of charged particles escape from the star surface. The electron stream moves along the magnetic axis. The electron stream is enveloped by proton-positron stream, which is generated by returning hard electrons accelerated by electromagnetic field of the star. 相似文献
11.
M. L. Fil'Chenkov 《Astronomische Nachrichten》1990,311(4):223-226
Within the framework of quantum mechanics in a curved space-time the transitions between energy levels of a charged particle (elementary particle, atomic nucleus) being in a Schwarzschild field are considered. The DeWitt conservative self-force acting on the charge is taken into account. Energy and intensity of the electric dipole radiation are calculated for charged particles in the field of miniholes with masses ranging from 1014 to 10−5 g. 相似文献
12.
I. H. Urch 《Astrophysics and Space Science》1977,48(1):231-236
The diffusion of charged particles in a turbulent magnetic field, but with no constant back-ground electromagnetic fields,
is discussed and expressions for the particle fluxes calculated. 相似文献
13.
Dynamics of charged particles and perpendicular diffusion in turbulent magnetic field 总被引:1,自引:0,他引:1
A test particle code is employed to explore the dynamics of charged particles and perpendicular diffusion in turbulent magnetic
field, where a three-dimensional (3D) isotropic turbulence model is used in this paper. The obtained perpendicular diffusion
at different particle energies is compared with that of the nonlinear guiding center (NLGC) theory. It is found that the NLGC
theory is consistent with test particle simulations when the particle energies are small. However, the difference between
the NLGC theory and test particle simulations tends to increase when the particle energy is sufficiently large, and the threshold
is related to the turbulence bend-over length. In the NLGC theory, the gyrocenter of a charged particle is assumed to follow
the magnetic field line. Therefore, when the particle has sufficiently large energy, its gyroradius will be larger than the
turbulence bend-over length. Then the particle can cross the magnetic field lines, and the difference between the test particle
simulations and NLGC theory occurs. 相似文献
14.
K. P. Chopra 《Planetary and Space Science》1961,5(4):288-291
A body moving in an ionized atmosphere acquires an electric charge through the processes of accretion of charged particles and emission of electrons by high energy photons. The moving charged body may then interact with the charged particles of the atmosphere and any pervading magnetic field to excite plasma waves. Of particular interest is the situation in which the body collects an ionized cloud in front of it. The motion of this ionized cloud in the atmosphere induces an electrostatic instability and causes a column of ionized gas to move ahead of the body. The electrostatic instability is conducive to the excitation of electrostatic oscillations which if already present are further enhanced. A magnetic field along the direction of motion assists in the formation of the ionized cloud. If the pervading magnetic field is of suitable weak strength, it may excite extraordinary electromagnetic waves. A pervading transverse magnetic field of suitable strength may cause the excitation of magnetohydrodynamic waves. 相似文献
15.
We have obtained an analytical solution to the equation of motion in the guiding center approximation for nonrelativistic charged particles in a reconnecting current sheet with a three-component magnetic field. Given the electric field attributable to magnetic reconnection, the solution describes stable and unstable three-dimensional particle orbits. We have found the domain of input parameters at which the motion is stable. A physical interpretation of the processes affecting the stability of the motion is given. Charge separation is shown to take place in the sheet during the motion: oppositely charged particles are localized mostly in different regions of the current sheet. A formula is derived for the particle energy in stable and unstable orbits. The results obtained by numerical and analytical methods are compared. 相似文献
16.
I. N. Toptygin 《Astronomy Letters》2007,33(4):259-269
We analyze the nonresonant generation of large-scale magnetic inhomogeneities near a shock front by accelerated particles. The MHD disturbances are generated by the electric current excited by relativistic particles in the preshock medium in the presence of weak large-scale density inhomogeneities. The MHD modes considered can be amplified by other resonant and nonresonant mechanisms related to the presence of relativistic particles. We estimate the magnetic fields and the energies to which charged particles can be accelerated in different phases of the interstellar medium by taking into account the random magnetic fields generated by the mechanism considered. 相似文献
17.
Synchro-CurvatureRadiation──弯曲磁场中一种新的、更普遍的辐射张家铝(中国科技大学天体物理中心合肥230026)郑广生(香港大学物理系)关键词同步辐射,曲率辐射,脉冲星磁层在脉冲星的辐射模型中,同步辐射和曲率辐射占有极其重要... 相似文献
18.
《天文和天体物理学研究(英文版)》2017,(1)
One of the most puzzling problems in astrophysics is to understand the anomalous resistivity in collisionless magnetic reconnection that is believed extensively to be responsible for the energy release in various eruptive phenomena. The magnetic null point in the reconnecting current sheet, acting as a scattering center, can lead to chaotic motions of particles in the current sheet, which is one of the possible mechanisms for anomalous resistivity and is called chaos-induced resistivity. In many interesting cases, however, instead of the magnetic null point, there is a nonzero magnetic field perpendicular to the merging field lines, usually called the guide field, whose effect on chaos-induced resistivity has been an open problem. By use of the test particle simulation method and statistical analysis, we investigate chaos-induced resistivity in the presence of a constant guide field. The characteristics of particle motion in the reconnecting region, in particular, the chaotic behavior of particle orbits and evolving statistical features, are analyzed. The results show that as the guide field increases, the radius of the chaos region increases and the Lyapunov index decreases. However, the effective collision frequency, and hence the chaos-induced resistivity, reach their peak values when the guide field approaches half of the characteristic strength of the reconnection magnetic field. The presence of a guide field can significantly influence the chaos of the particle orbits and hence the chaos-induced resistivity in the reconnection sheet, which decides the collisionless reconnection rate. The present result is helpful for us to understand the microphysics of anomalous resistivity in collisionless reconnection with a guide field. 相似文献
19.
20.
Janet E. Drew Daniel Proga & James M. Stone 《Monthly notices of the Royal Astronomical Society》1998,296(1):L6-L10
The generation of magnetic fields by a battery, operating in an ion–electron plasma around a Kerr black hole, is studied in the 3+1 split of the Kerr metric. It is found that the gravitomagnetic contributions to the electron partial pressure are able to drive currents. The strength of the equilibrium magnetic field should be higher than for the classical Biermann battery, which is found to operate in this relativistic context as well, since the gravitomagnetic driving terms can less easily be quenched than the classical ones. In axisymmetry the battery can induce only toroidal magnetic fields. Once a toroidal magnetic field is present, however, the coupling of gravitomagnetic and electromagnetic fields generates a poloidal magnetic field even in axisymmetry. A rotating black hole, embedded in plasma, will therefore always generate toroidal and poloidal magnetic fields. 相似文献