共查询到20条相似文献，搜索用时 15 毫秒
1.
I. H. Urch 《Astrophysics and Space Science》1991,178(2):185-195
The Fokker-Planck equation which describes the motion of charged particles in a random electromagnetic field is derived from the Liouville equation by a new method. The size of the perturbing magnetic field, for the Fokker-Planck equation to be valid, is calculated in a regime appropriate for cosmic-ray diffusion. 相似文献
2.
V. V. Tamoykin 《Astrophysics and Space Science》1972,16(1):120-129
Radiation of a uniformly moving charged particle in a medium with weak, random inhomogeneities of dielectric permittivity is considered. The expression for the charge energy losses is obtained by the method of radiation reaction using the tensor of the effective permittivity. The limiting cases of small-and large-scale inhomogeneities are studied. Peculiarities of energy losses near the threshold of Cherenkov radiation are clarified. 相似文献
3.
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
4.
The extended nonthermal X-ray emission of extragalactic jets like Centaurus A can only be explained by in situ particle acceleration. The only energy source in the entire jet region is the magnetic field. Magnetic reconnection can convert the free energy stored in the helical configuration to particle kinetic energy. In the collisionless magnetized jet plasma, the inertia-driven reconnection is operating in a highly filamentary magnetic flux rope, and this results in a continuously charged particle acceleration. The synchrotron radiation of these particles can cause the observed X-ray emission in Centaurus A. 相似文献
5.
The effect of the solar wind on the spectrum of cosmic rays accelerated in the Galaxy is studied. The coefficient of cosmic-ray diffusion in the interplanetary turbulent magnetic field is assumed to be independent of the particle energy and a power-law function of the distance from the Sun. The particle spectrum at the heliospheric boundary is specified as a power-law function of the total particle energy. 相似文献
6.
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
7.
The physical processes responsible for transient cosmic-ray decreases have been investigated for two types of interplanetary shock events associated with helium enhancement (He-shocks) and those not associated with helium enhancement (non-He-shocks). The Calgary cosmic-ray neutron monitor data and the interplanetary field data have been subjected to a superposed-epoch Chree analysis. The difference in the profiles of the cosmic-ray intensity have been compared with the interplanetary field data and its variance. It is suggested that the turbulence sheath following the shock front is very effective and of major importance for producing cosmic-ray decreases. A simple model has been proposed to explain the observations which show that a Forbush decrease modulating region consists of a shock front associated with a plasma sheath in which the magnetic field is turbulent and the sheath, in turn, is followed by an ejected plasma cloud having ordered structure and high magnetic field strength. 相似文献
8.
E. Martínez-Gómez H. J. Durand-Manterola H. Pérez de Tejada 《Astrophysics and Space Science》2006,306(4):259-267
Voyager's plasma probe observations suggest that there are at least three fundamentally different plasma regimes in Saturn:
the hot outer magnetosphere, the extended plasma sheet, and the inner plasma torus. At the outer regions of the inner torus
some ions have been accelerated to reach energies of the order of 43 keV. We develop a model that calculates the acceleration
of charged particles in the Saturn's magnetosphere. We propose that the stochastic electric field associated to the observed
magnetic field fluctuations is responsible of such acceleration. A random electric field is derived from the fluctuating magnetic
field – via a Monte Carlo simulation – which then is applied to the momentum equation of charged particles seeded in the magnetosphere.
Taking different initial conditions, like the source of charged particles and the distribution function of their velocities,
we find that particles injected with very low energies ranging from 0.129 eV to 5.659 keV can be strongly accelerated to reach
much higher energies ranging from 22.220 eV to 9.711 keV as a result of 125,000 hitting events (the latter are used in the
numerical code to produce the particle acceleration over a predetermined distance). 相似文献
9.
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
10.
In this paper we provide two new alternative derivations of the equation of transport for cosmic-ray particles in the interplanetary region. Both derivations are carried out by using particle positionr and timet in a frame of reference fixed in the solar system, and the particle momentump is specified relative to a local frame of reference moving with the solar wind. The first derivation is carried out by writing down a continuity equation for the cosmic rays, taking into account particle streaming and energy changes, and subsequently deriving the streaming and energy change terms in this equation. The momentum change term in the continuity equation, previously considered to be due to the adiabatic deceleration of particles in the expanding magnetic fields carried by the solar wind, appears in the present analysis as a dynamic effect in which the Lorentz force on the particle does not appear explicitly. An alternative derivation based on the ensemble averaged Liouville equation for charged particles in the stochastic interplanetary magnetic field using (r, p,t) as independent coordinates is also given. The latter derivation confirms the momentum change interpretation of the first derivation. We also provide a new derivation of the adiabatic rate as a combination of inverse-Fermi and betatron deceleration processes. 相似文献
11.
The equation for the two-particles cosmic-ray distribution function is derived by means of the Boltzmann kinetic equation averaging. This equation is valid for arbitrary ratio of regular and random parts of the magnetic field. For small energy particles the guiding-center approximation is used. On the basis of the derived equation the dependence between power spectra of cosmic-ray intensity and random magnetic field is obtained. If power spectra are degree functions for high energy particles ( 10 GeV nucleon–1), then the spectral exponent of magnetic field lies between and –2, where is the spectral exponent of cosmic-ray power spectra. The experimental data concerning moderate energy particles are in accordance with =, which demonstrates that the magnetic fluctuations are isotropic or cosmic-ray space gradient is small near the Earth orbit. 相似文献
12.
A. A. Abdujabbarov A. A. Tursunov B. J. Ahmedov A. Kuvatov 《Astrophysics and Space Science》2013,343(1):173-179
The collision of test charged particles in the vicinity of an event horizon of a weakly magnetized non-rotating black hole with gravitomagnetic charge has been studied. The presence of the external magnetic field decreases the innermost stable circular orbits (ISCO) radii of charged particles. The opposite mechanism occurs when there is nonvanishing gravitomagnetic charge. For a collision of charged particle moving at ISCO and the neutral particle falling from infinity the maximal collision energy can be decreased by gravitomagnetic charge in the presence of external asymptotically uniform magnetic field. 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.
Hamid M. K. Al-Naimiy 《Astrophysics and Space Science》1978,53(1):3-11
The radiation of a charge rotating in a circle with the constant velocity (in the external magnetic field) in the isotropic plasma with random inhomogeneities of the electron density has been considered. A general expression is obtained for the radiation intensity at thenth harmonic, which is a generalization of the known Shott formula. In the ultra-relativistic case the conditions are clarified under which the inhomogeneity effect on the form of the spectrum of radiation from a particle is essential. An asymptotic formula is derived for the spectral intensity in the region of sufficiently low frequencies. The mechanism of transient radiation in this case is shown to prevail over the synchrotron one. 相似文献
15.
Influence of magnetic clouds on cosmic ray intensity variation 总被引：1，自引：0，他引：1
The data from a high counting rate neutron monitor has been analysed to study the nature of galactic cosmic-ray transient modulation associated with three classes of magnetic clouds, i.e., clouds associated with shock, stream interface and cold magnetic enhancement.It is found that the decreases in cosmic-ray intensity which are associated with clouds preceded by a shock, are very high (Forbush-type) and these decreases start earlier than the arrival of the cloud at the Earth. From the study of the time profile of these decreases it is found that the onset time of a Forbush-type decrease produced by a shock-associated cloud starts nearly at the time of arrival of the shock front at the Earth and the recovery is almost complete within a week.The decreases in cosmic-ray intensity associated with clouds followed by a stream interface are smaller in magnitude and larger in duration. The depression starts on the day of the arrival of the cloud.The decreases associated with the third category of clouds, i.e., clouds associated with cold magnetic enhancement (a region in which plasma temperature is anomalously low and the magnetic field strength is enhanced) are of still smaller amplitude and duration. The decrease in this case starts on the day the cloud arrives at the Earth.It seems that the Forbush decrease modulating region consists of a shock front followed by a plasma sheath in which the field intensity is high and turbulent. The amplitude of decrease is related to the field magnitude and the speed of the cloud. Both shocked plasma and the magnetic cloud are influential in determining the time profile of these decreases. In our view it is not the magnetic field strength or the topology alone which is responsible for the cosmic-ray depression. The most likely additional effect is the increased degree of turbulence. 相似文献
16.
The problem of effective transform of Poynting flux energy into the kinetic energy of relativistic plasma outflow in a magnetosphere
is considered. In this article we present an example of such acceleration. In order to perform it, we use the approach of
ideal axisymmetric magnetohydrodynamics (MHD). For highly magnetized plasma outflow we show that a linear growth of Lorentz
factor with a cylindrical distance from the rotational axis is a general result for any field configuration in the sub-magnetosonic
flow. In the far region the full magnetohydrodynamics problem for one-dimensional flow is considered. It turns out that the
effective plasma outflow acceleration is possible in the paraboloidal magnetic field. It is shown that such an acceleration
is due to the drift of charged particles in the crossed electric and magnetic field. The clear explanation of the absence
of acceleration in the monopole magnetic field if given.
相似文献
17.
Marco Regis 《Astroparticle Physics》2011,35(4):170-176
Fluctuations in the Galactic synchrotron emission can be traced by the angular power spectrum of radio maps at low multipoles. At frequencies below few GHz, large-scale anisotropies are mainly induced by magnetic field turbulence, since non-thermal electrons radiating at these frequencies are uniformly distributed over the scales of magnetic field inhomogeneities. By performing an analysis of five radio maps, we extract constraints on turbulence spectral index and halo scale. Results favour a power spectrum significantly flatter than for 3D Kolmogorov-like turbulence, and a thin halo. This can be interpreted as an indication supporting non-conventional models of propagation of cosmic-ray particles in the Galaxy, or as a suggestion of a spectral-index break in the observed magnetic turbulence power spectrum. 相似文献
18.
《Planetary and Space Science》2007,55(14):2164-2172
Both the MARSIS ionospheric sounder and the charged particle instrument package ASPERA-3 are experiments on board the Mars Express spacecraft. Joint observations have shown that events of intense ionospheric electron density enhancements occur in the lower ionosphere of magnetic cusp regions, and that these enhancements are not associated with precipitation of charged particles above a few hundred electron volts (<300 eV). To account for the enhancement by particle precipitation, electron fluxes are required with mean energy between 1 and 10 keV. No ionizing radiation, neither energetic particles nor X-rays, could be identified, which could produce the observed density enhancement only in the spatially limited cusp regions. Actually, no increase in ionizing radiation, localized or not, was observed during these events. It is argued that the process causing the increase in density is controlled mainly by convection of ionosphere plasma driven by the interaction between the solar wind and crustal magnetic field lines leading to excitation of two-stream plasma waves in the cusp ionosphere. The result is to heat the plasma, reduce the electron–ion recombination coefficient and thereby increase the equilibrium electron density. 相似文献
19.
《New Astronomy Reviews》2002,46(2-7):387-391
We have applied an effective numerical scheme for cosmic-ray transport to 3D MHD simulations of jet flow in radio galaxies (see the companion paper by Jones et al. herein). The marriage of relativistic particle and 3D magnetic field information allows us to construct a rich set of ‘synthetic observations’ of our simulated objects. The information is sufficient to calculate the ‘true’ synchrotron emissivity at a given frequency using explicit information about the relativistic electrons. This enables us to produce synchrotron surface-brightness maps, including polarization. Inverse-Compton X-ray surface-brightness maps may also be produced. First results intended to explore the connection between jet dynamics and electron transport in radio lobes are discussed. We infer lobe magnetic field values by comparison of synthetically observed X-ray and synchrotron fluxes, and find these ‘inverse-Compton’ fields to be quite consistent with the actual RMS field averaged over the lobe. The simplest minimum energy calculation from the synthetic observations also seems to agree with the actual simulated source properties. 相似文献
20.
Ajoy Kumar Dasgupta 《Astrophysics and Space Science》1979,62(1):241-243
Transition radiation is emitted when a charged particle traverses a boundary separating two media. Such radiation must therefore be emitted as X-rays and ultraviolet radiation, from a medium where cosmic-ray electrons pass through dust grains. Calculation shows that transition radiation emitted in this way might account for soft X-rays emission from relativistic charged dust grains in the intergalactic medium (IGM). This could be a help in understanding the IGM as well as an indirect method of measuring the energies of high energy particles. 相似文献