共查询到20条相似文献，搜索用时 15 毫秒
1.
This review describes the basic theory of cosmic ray acceleration by shocks including the plasma instabilities confining cosmic rays near the shock, the effect of the magnetic field orientation, the maximum cosmic ray energy and the shape of the cosmic ray spectrum. Attention is directed mainly towards Galactic cosmic rays accelerated by supernova remnants. 相似文献
2.
Astrophysics - We study the modulation of galactic cosmic rays due to magnetic clouds observed during solar cycles 23 and 24 (1996-2018). We utilize solar wind plasma and field data together with... 相似文献
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4.
One-, two- and three-dimensional numerical results of the non-linear interaction between cosmic rays and a magnetic field are presented. These show that cosmic ray streaming drives large-amplitude Alfvénic waves. The cosmic ray streaming energy is very efficiently transferred to the perturbed magnetic field of the Alfvén waves, and the non-linear time-scale of the growth of the waves is found to be very rapid, of the order of the gyro-period of the cosmic ray. Thus, a magnetic field of interstellar values, assumed in models of supernova remnant blast wave acceleration, would not be appropriate in the region of the shock. The increased magnetic field reduces the cosmic ray acceleration time and so increases the maximum cosmic ray energy, which may provide a simple and elegant resolution to the highest energy Galactic cosmic ray problem, where the cosmic rays themselves provide the fields necessary for their acceleration. 相似文献
5.
One dimensional numerical results of the non-linear interaction between cosmic rays and a magnetic field are presented. These
show that cosmic ray streaming drives large amplitude Alfvénic waves. The cosmic ray streaming energy is very efficiently
transfered to the perturbed magnetic field of the Alfvén waves. Thus a magnetic field of interstellar values, assumed in models
of supernova remnant blast wave acceleration, would not be appropriate in the region of the shock. The increased magnetic
field reduces the acceleration time and so increases the maximum cosmic ray energy, which may provide a simple and elegant
resolution to the highest energy galactic cosmic ray problem were the cosmic rays themselves provide the fields necessary
for their acceleration.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
The hydrostatic equilibrium of the gas field system is studied in the halo. Cosmic-ray distribution is considered independently from the magnetic field on the basis of the diffusion model of the propagation of cosmic rays. We show that the cosmic rays extend in the halo to distances of a few kiloparsecs. The magnetic field decreases slowly with height above the galactic plane. 相似文献
7.
The flux rate of cosmic rays incident on the Earth’s upper atmosphere is modulated by the solar wind and the Earth’s magnetic
field. The amount of solar wind is not constant due to changes in solar activity in each solar cycle, and hence the level
of cosmic ray modulation varies with solar activity. In this context, we have investigated the variability and the relationship
of cosmic ray intensity with solar, interplanetary, and geophysical parameters from January 1982 through December 2008. Simultaneous
observations have been made to quantify the exact relationship between the cosmic ray intensity and those parameters during
the solar maxima and minima, respectively. It is found that the stronger the interplanetary magnetic field, solar wind plasma
velocity, and solar wind plasma temperature, the weaker the cosmic ray intensity. Hence, the lowest cosmic ray intensity has
good correlations with simultaneous solar parameters, while the highest cosmic ray intensity does not. Our results show that
higher solar activity is responsible for a higher geomagnetic effect and vice versa. 相似文献
8.
V. S. Ptuskin 《Astrophysics and Space Science》1979,61(2):259-265
A modification of the diffusional motion of cosmic rays in a large scale turbulent field is considered. The partial dragging of particles in the arbitrarily wandering magnetic field lines may lead to the creation of a new regime of diffusion of cosmic rays in the Galaxy. 相似文献
9.
E. N. Parker 《Astrophysics and Space Science》1973,24(1):279-288
The origin and behavior of cosmic rays in the Galaxy depends crucially upon whether the galactic magnetic field has a closed topology, as does the field of Earth, or whether a major fraction of the lines of force connect into extragalactic space. If the latter, then cosmic rays could be of extragalactic origin, or they could be of galactic origin, detained in the Galaxy by the scattering offered by hydromagnetic waves, etc. If, on the other hand, the field is largely closed, then cosmic rays cannot be of extragalactic origin (at least below 1016 eV). They must be of galactic origin and escape because their collective pressure inflates the galactic field and they push their way out.This paper examines the structure of a galactic field that opens initially into intergalactic space and, with the inclusion of turbulent diffusion, finds no possibility for maintaining a significant magnetic connection with an extragalactic field. Unless some mechanism can be found, we are forced to the conclusion that the field is closed, that cosmic rays are of galactic origin, and that cosmic rays escape from the Galaxy only by pushing their way out. 相似文献
10.
Since collective plasma behavior may determine important transport processes (e.g., plasma diffusion across a magnetic field) in certain cosmic environments, it is important to delineate the parameter space in which weakly ionized cosmic gases may be characterized as plasmas. In this short note, we do so. First, we use values for the ionization fraction given in the literature, wherein the ionization is generally assumed to be due primarily to ionization by cosmic rays. We also discuss an additional mechanism for ionization in such environments, namely, the photoelectric emission of electrons from cosmic dust grains in an interstellar FUV radiation field. Simple estimates suggest that under certain conditions this mechanism may dominate cosmic ray ionization, and possibly also the photoionization of metal atoms by the interstellar FUV field, and thereby lead to an enhanced ionization level. 相似文献
11.
S. V. Chalov 《Astrophysics and Space Science》1988,148(1):175-187
A criterion of the instability of a flow of a thermal plasma and cosmic rays in front of an oblique MHD shock wave with respect to short-wavelength magnetosonic disturbances is derived. The dependence of a cosmic-ray diffusion tensor on a plasma density and a large-scale magnetic field is taken into account. The most unstable disturbances propagate at an angle to the magnetic field if diffusion is strongly anisotropic. In some cases the most strong instability connects with the off-diagonal terms of the diffusion tensor. 相似文献
12.
V. G. Kryvdyk 《Kinematics and Physics of Celestial Bodies》2009,25(6):277-301
We investigate a transformation of a magnetic field and plasma in nonhomogeneous magnetospheres of collapsing stars with a
dipole initial magnetic field and certain initial energy distributions of particles in the magnetosphere as the power low,
relativistic Maxwell and Boltzmann. The betatron mechanism of the charged particles acceleration in a collapsing star’s magnetosphere
is considered. When a magnetized star is compressed in the stage of the gravitational collapse, the magnetic field increases
strongly. This variable magnetic field generates a vortical electric field. Our calculations show that this electric field
will accelerate charged particles up to relativistic velocities. Thus, collapsing stars may be sources of high energy cosmic
rays in our galaxy as in others. The acceleration of particles during the collapse happens mostly in polar regions of the
magnetosphere that leads to polar relativistic streams (jets) formation. When moving in a magnetic field, these particles
will generate nonthermal electromagnetic radiation in a broad electromagnetic wavelength band from radioto gamma rays. Thus,
in the stage of the gravitational collapse, relativistic jets are formed in stellar magnetospheres. These jets are powerful
sources of the nonthermal electromagnetic radiation. 相似文献
13.
In this paper we demonstrate the importance of cosmic rays for the dynamics of the interstellar medium. We present the first 3D-MHD numerical simulations of the Parker instability triggered by cosmic rays accelerated in randomly distributed supernova remnants. We show that in the presence of galactic rotation a net radial magnetic field is produced as a result of the cosmic ray injection and Coriolis force. This process provides a possibility of very efficient magnetic field amplification within the general frame of so called fast galactic dynamo proposed by Parker (1992). 相似文献
14.
We review the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding Universe filled with the cosmic plasma and provide a critical review of the literature on the subject. We put special emphasis on the prospects for observational tests of the proposed cosmological magnetogenesis scenarios using radio and gamma-ray astronomy and ultra-high-energy cosmic rays. We argue that primordial magnetic fields are observationally testable. They lead to magnetic fields in the intergalactic medium with magnetic field strength and correlation length in a well defined range.We also state the unsolved questions in this fascinating open problem of cosmology and propose future observations to address them. 相似文献
15.
V. H. Kryvdyk 《Kinematics and Physics of Celestial Bodies》2007,23(2):77-83
We examine the acceleration of cosmic rays in the magnetospheres of collapsing stars with initial dipole magnetic fields and various initial energy distributions of charged particles in their magnetospheres (the exponential, relativistic Maxwellian, and Boltzmann distributions were considered). When a magnetized star contracts at the gravitational collapse stage, its magnetic field grows considerably. Such a variable magnetic field generates an eddy electric field. Our calculations suggest that this electric field can accelerate charged particles to relativistic energies. In this way collapsing stars can be sources of high-energy cosmic rays in our Galaxy as well as in other galaxies. 相似文献
16.
The transport of cosmic rays in the interplanetary medium is considered in terms of the kinetic equation describing the energetic
particle scattering by magnetic irregularities and their focusing by the regular interplanetary magnetic field. The analytical
expression for solar cosmic ray distribution function in the approximation of radial regular magnetic field is obtained and
the evolution of energetic particle angular distribution is analyzed. The obtained results can be used for the analysis of
ground-level enhancements of cosmic ray intensity. 相似文献
17.
In this paper we demonstrate the importance of cosmic rays for the dynamics of the interstellar medium. We present the first
3D-MHD numerical simulations of the Parker instability triggered by cosmic rays accelerated in supernova remnants. We show
that in the presence of galactic rotation a net radial magnetic field is produced as a result of the cosmic ray injection.
This process provides a very efficient magnetic field amplification within the general frame of so called fast galactic dynamo proposed by Parker (1992).
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
18.
Lev I. Dorman 《Astrophysics and Space Science》1998,264(1-4):443-455
Influence of cosmic ray pressure and kinetic stream instability on space plasma dynamics and magnetic structure are considered.
It is shown that in the outer Heliosphere are important dynamics effects of galactic cosmic ray pressure on solar wind and
interplanetary shock wave propagation as well as on the formation of terminal shock wave of the Heliosphere and subsonic region
between Heliosphere and interstellar medium. Kinetic stream instability effects are important on distances more than 40–60
AU from the Sun: formation of great anisotropy of galactic cosmic rays in about spiral interplanetary magnetic field leads
to the Alfven turbulence generation by non isotropic cosmic ray fluxes. Generated Alfven turbulence influences on cosmic ray
propagation, increases the cosmic ray modulation, decreases the cosmic ray anisotropy and increases the cosmic ray pressure
gradient in the outer Heliosphere (the later is also important for terminal shock wave formation).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Hirokazu Yoshimura 《Solar physics》1977,54(1):229-258
The simultaneous enhancement or subsidence of both the high-speed solar wind streams and the galactic cosmic rays in the minimum or the maximum phase of the solar cycle are interpreted in a unified manner by the concept of geometrical evolution of the general magnetic field of the corona-heliomagnetosphere system. The coronal general magnetic field evolves from an open dipole-like configuration in the minimum phase to a closed configuration with many loop-like formations in the maximum phase of the solar cycle. This concept, developed in a theoretical solar-cycle model driven by the dynamo action of the global convection, is examined and found to be valid by studying the evolution of the coronal general magnetic field calculated from the observed surface general magnetic field of 1959–1974. It is also found that the energy density of the poloidal component of the general surface field, from which the coronal field originates, attained a maximum in the maximum phase and showed a evolution with virtually no phase delay with respect to that of the toroidal component of the field, to which the sunspot activity is related. The subsidence of the high-speed solar wind in the maximum phase is understood as a braking of the solar wind streams by the tightly closed and strong coronal field lines in the lower corona in the maximum phase. The field lines of the heliomagnetosphere, which originate from the coronal field lines drawn by the solar wind, are inferred to be also more tightly closed at the heliopause in the maximum phase than in the minimum phase. The decrease of the galactic cosmic rays in the maximum phase (known as the Forbush's negative correlation between the galactic cosmic ray intensity and the solar activity or the Forbush solar-cycle modulation of the galactic cosmic rays) is interpreted as a braking of the cosmic rays by the closed magnetic field lines at the heliopause. The observed phase lag (approximately one year) of the galactic cosmic ray modulation with respect to the evolution of the solar cycle, and the observed absence of the gradient of the total cosmic ray intensity between 1 AU and 8 AU, are discussed to support this view of the cosmic ray modulation at the remote heliopause, and reject other hypotheses to explain the phenomenon in terms of the magnetic irregularities of various kinds carried by the solar wind: The short-term Forbush decrease at a time of a flare shows that the magnetic irregularities can react on the cosmic rays relatively near the Sun if they even played a dominant role in the long-term modulation. The concept of the general magnetic field of the corona and the surface is also used to understand the basic nature of the surface field itself, by comparing the geometry of the calculated coronal field lines with the eclipse photographs of the corona, and by discussing, in the context of the coronal general magnetic field associated with the solar cycle, the process of the emergence of the coronal field lines from the interior and the formation of the transequatorial arches and loops connecting the two hemispheres in the corona. 相似文献
20.
We have studied anisotropy of cosmic rays with an Extensive Air Shower(EAS) array in Tehran 1200 m above sea level. In analyzing
the data set, we have used appropriate techniques of analysis and considered environmental effects. An asymmetry has been
observed in the azimuthal distribution of EAS of cosmic rays because of magnetic field of the Earth. 相似文献