共查询到20条相似文献，搜索用时 62 毫秒
1.
The propagation of radioactive nuclei of cosmic rays in a flat diffusion galactic model (sources and the main gaseous mass are concentrated in the galactic disc) is considered. The corresponding results are not reducible to the results of a simple homogeneous model. It is shown that the recent data on the Be10 nuclei abundance in cosmic rays do not contradict the occurrence of a large cosmic ray halo. 相似文献
2.
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
3.
We investigate the problem of transition from galactic cosmic rays to extragalactic ultra-high energy cosmic rays. Using the model for extragalactic ultra-high energy cosmic rays and observed all-particle cosmic ray spectrum, we calculate the galactic spectrum of iron nuclei in the energy range 108–109 GeV. The flux and spectrum predicted at lower energies agree well with the KASCADE data. The transition from galactic to extragalactic cosmic rays is distinctly seen in spectra of protons and iron nuclei, when they are measured separately. The shape of the predicted iron spectrum agrees with the Hall diffusion. 相似文献
4.
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
5.
Yu. L. Kolesnyk A. I. Klyuyeva B. A. Shakhov Yu. I. Fedorov 《Kinematics and Physics of Celestial Bodies》2016,32(6):265-275
The effect of high-speed recurrent solar wind streams from coronal holes on the galactic cosmic rays intensity is investigated. The distribution of galactic cosmic rays for different solar cycles is considered based on the data of the world network of neutron monitors. Within the inhomogeneous model, which includes a homogeneous background and regions of high-speed streams (HSS’s), the transport equation has been solved and the effect of HSS’s on the spatial distribution of galactic cosmic rays is estimated. It is shown that theoretical calculations are agreed with the experimental results obtained for 2000–2014 under different assumptions about the mean free path of cosmic rays in the corresponding period of HSS’s. 相似文献
6.
The case is made for most cosmic rays having come from galactic sources. ‘Structure’, i.e. a lack of smoothness in the energy spectrum, is apparent, strengthening the view that most cosmic rays come from discrete sources, supernova remnants being most likely. 相似文献
7.
A new type of galactic outflow phenomenon has been discovered and published under the name of thermal spur by Mülleret al. (1987). It is argued that this outflow consists of relativistic pair plasma with an admixture of partially ionized hydrogen and cosmic rays, escaping from a large Hii region. This chimney serves as a substantial leak for the cosmic rays, i.e., may be an essential part of the galactic foundtain. 相似文献
8.
The structure of the cosmic ray electron halo of a starburst galaxy depends strongly on the nature of galactic wind and the
configuration of the magnetic field. We have investigated these dependencies by solving numerically the propagation of electrons
originating in starburst galaxies, most likely in supernova remnants. The calculations are made for several models for the
galactic winds and for the configuration of the magnetic fields for comparison with observations. Our simulation of a quasi-radio
halo reproduces both the extended structure of ∼9 kpc and the subtle hollow structure near the polar region of the radio halo
that are observed in the starburst galaxy NGC 253. These findings suggest the existence of strong galactic wind in NGC 253.
相似文献
9.
Cosmic rays are a sample of solar, galactic and extragalactic matter. Their origin and properties are one of the most intriguing question in modern astrophysics. The most energetic events and active objects in the Universe: supernovae explosion, pulsars, relativistic jets, active galactic nuclei, have been proposed as sources of cosmic rays although unambiguous evidences have still to be found. Electrons, while comprising ∼1% of the cosmic radiation, have unique features providing important information regarding the origin and propagation of cosmic rays in the Galaxy that is not accessible from the study of the cosmic-ray nuclear components due to their differing energy-loss processes. In this paper we will analyse, discussing the experimental uncertainties and challenges, the most recent measurements on cosmic-ray nuclei and, in particular, electrons with energies from tens of GeV into the TeV region. 相似文献
10.
Zhou Da-zhuang
K. K. Tang
《Chinese Astronomy and Astrophysics》1991,15(4):416-422We calculate the spectrum of the diffuse cosmic gamma ray in the single and double leaky box models for several galactic distribution laws of cosmic rays and hdydrogen. The results show that LI Ti-pei's distribution law for the cosmic rays is the best and that the number of interstellar hydrogen molecules should be less than Gordon's value divided by 1.7. The observed spectrum of gamma rays can be reproduced by a suitable choice of the galactic distributions within certain ranges. 相似文献
11.
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
12.
A. J. Owens 《Astrophysics and Space Science》1976,40(2):357-367
The general solution for the distribution of ages for primary galactic cosmic rays is given for a class of steady-state, bounded models of cosmic-ray diffusion in the Galaxy. Both one-and threedimensional models are considered, with point sources and distributed sources. In all models, the age distribution, is approximately exponential for ages longer than the average age, although for shorter ages the distribution depends on the details of the model. The leaky-box model, with an exponential age distribution, is thus a good approximation to most diffusive models. It is shown that one-dimensional (disk) models are consistent with both age and anisotropy data for galactic cosmic rays regardless of whether production takes place near the galactic center or throughout the disk. 相似文献
13.
Observed events of ultra-high energy cosmic rays may indicate a hard component for the energy spectrum of their flux, which might have origin in the decay of long-lived vortons presumably condensed in the galactic halo. To be consistent with the needed present density, vortons may have been formed during the breaking of an abelian symmetry contained in a large GUT group like E6 and a part of them could have survived the destabilization caused by the electroweak transition. 相似文献
14.
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
15.
Stefano Gabici Felix A. Aharonian Pasquale Blasi 《Astrophysics and Space Science》2007,309(1-4):365-371
It is believed that the observed diffuse gamma-ray emission from the galactic plane is the result of interactions between
cosmic rays and the interstellar gas. Such emission can be amplified if cosmic rays penetrate into dense molecular clouds.
The propagation of cosmic rays inside a molecular cloud has been studied assuming an arbitrary energy and space dependent
diffusion coefficient. If the diffusion coefficient inside the cloud is significantly smaller compared to the average one
derived for the galactic disk, the observed gamma-ray spectrum appears harder than the cosmic ray spectrum, mainly due to
the slower penetration of the low energy particles towards the core of the cloud. This may produce a great variety of gamma-ray
spectra. 相似文献
16.
An analysis has been made of the fraction of ultra high energy cosmic rays (above 1018 eV) which could be due to processes involved in two possible ‘Models’. The first is the Giant Magnetic Halo Model and the second is the Dark Matter Halo Model. We find that the former, in which heavy nuclei are trapped in a giant halo, fails for energies above about 3 × 1019 eV. For the Dark Matter Halo Model, in which relic particles follow the “conventional” dark matter and whose decays give ultra high energy cosmic rays, the predicted anisotropies are much higher than those observed. The lack of observation of a finite flux from the Andromeda Galaxy means that the conclusion is insensitive to the spatial scale size of the assumed halo distribution. It is concluded that less than 10% of the ultra high energy cosmic rays come from relic particles in the Galactic halo. 相似文献
17.
18.
With the help of empirical data concerning the latitudinal distribution of galactic gamma rays the contribution of inverse Compton scattered gamma rays is calculated using various models concerning the distribution of high energy cosmic ray electrons perpendicular to the galactic plane. It is shown that gamma ray astronomy from regions with vanishing stellar and interstellar matter densities at energies greater than 100 MeV provides instructive information on the cosmic ray electron density. We find evidence for the existence of a broad galactic electron disk with a total thickness of at least 6.4 kpc. The uncertainties of the cosmic ray electron spectrum measurements above 100 GeV imply an additional uncertainty in the inverse Compton source function of at least a factor 6. 相似文献
19.
Yu. I. Fedorov B. A. Shakhov Yu. L. Kolesnyk 《Kinematics and Physics of Celestial Bodies》2017,33(1):1-12
The process of heliospheric modulation of intensity of galactic cosmic rays is investigated by solving the transport equation. The spatial-energetic distribution of cosmic rays in the present epoch and in the past is analyzed. It is demonstrated that the particle density and the energy density of cosmic rays in the Solar System in the distant past were much lower than the corresponding current values. The cosmic ray intensity modulation in the early heliosphere was especially strong in the case of low-energy particles. 相似文献
20.
The determination of the origin of cosmic rays with observed energies in excess of 1017 eV that exceed the expected energies of cosmic rays accelerated by supernova remnants in the galaxy is a pressing problem in modern astrophysics. Hypernova remnants are one of the possible galactic sources of cosmic rays with energies of up to 1019 eV. Hypernovae constitute a class of extremely powerful supernova explosions, whose supposed progenitors are massive Wolf-Rayet stars. We analyze the special aspects of acceleration of cosmic rays in hypernova remnants that expand in wind bubbles of Wolf-Rayet progenitor stars. We show that these cosmic rays may attain maximum energies of 1018 eV even with a relatively conservative choice of acceleration parameters and account for tens of percent of the total cosmic ray flux observed in the vicinity of the earth in the energy range of 1016–1018 eV if the galactic hypernova explosion rate in the modern epoch reaches ? S ～ 10?4 year?1. 相似文献