共查询到20条相似文献，搜索用时 15 毫秒
1.
Kunitomo Sakurai 《Solar physics》1971,17(2):459-467
Except for protons, the chemical composition of solar cosmic rays is very similar to the abundance of the elements at the photosphere of the Sun. If we consider the relative abundance ratio of protons to -particles (P/) at constant rigidity, this ratio is highly variable from one solar cosmic ray event to another. This ratio observed at the Earth, however, decreases monotonically with time from the onset of solar flares and, furthermore, is dependent on the heliocentric distance of the parent flares from the central meridian of the solar disk. P/'s which have been measured before the onset of SC geomagnetic storms change from 1.5 to 50 or more, being a function of the westward position of the source from the east limb of the Sun. These variations with respect to time and heliocentric distance suggest that the propagation of solar cosmic rays is strongly modulated in the interplanetary space. The major part of the -particles seem to propagate as if they are trapped within the magnetic clouds which produce SC geomagnetic and cosmic ray storms at the earth.The chemical composition and rigidity spectra of solar cosmic rays suggest that solar cosmic rays are mainly accelerated by the Fermi mechanism in solar flares. The observed variation of P/'s is produced mainly through the difference between the propagation characteristics of protons and -particles.NAS-NRC Associate with NASA. 相似文献
2.
The results of the determination of the fission track age of the Brahin pallasite are presented. Crystals of phosphates (stanfieldites), with an enhanced uranium concentration, were found directly in the investigated samples. Fossil tracks in them are represented by two generations. The distribution and partial annealing of first-generation track lengths point to a shock/thermal event at an early stage in the cosmic history of the pallasite. The value of the fission track age, registering the time of its passage, was computed from second-generation tracks. It was shown that the second generation is represented mainly by tracks of the spontaneous fission of 238U and 244Pu nuclei (Pu/U 4). The calculations performed made it possible to establish that the last intensive thermal event in the cosmic history of the Brahin pallasite occurred 4.26–4.20 billion years ago. The temperature of the reheating of its parent body did not rise above 500°C. The excellently preserved character of the second-generation tracks provides evidence that the pallasite underwent subsequent cosmic evolution in mild conditions. 相似文献
3.
Paul A. Laviolette 《Earth, Moon, and Planets》1987,37(3):241-286
It is proposed that outbursts of cosmic ray electrons from the Galactic Center penetrate the Galaxy relatively undamped and are able to have a major impact on the Solar System through their ability to vaporize and inject cometary material into the interplanetary environment. It is suggested that one such superwave, passing through the Solar System toward the end of the Last Ice Age, was responsible for producing major changes in the Earth's climate and for indirectly precipitating the terminal Pleistocene extinction episode. The high concentrations of 10Be, NO3
–, Ir and Ni observed in Late Wisconsin polar ice are consistent with this scenario. The intensities of the Galactic nonthermal radio background and diffuse X-ray emission ridge are shown to vary with Galactic longitude in the same manner as electron intensity along the proposed superwave event horizon. The high luminosities and unusual structural features which characterize the Crab Nebula and Cassiopeia A are shown to be attributable to the fact that these remnants happen to coincide with this event horizon and are being externally impacted by an intense volley of relativistic electrons travelling from the Galactic Center direction. The same cosmic ray volley is also shown to be able to account for the unusual structure of the extended radio source CTB 80. 相似文献
4.
The investigation of supernova remnants (SNRs) across the electromagnetic spectrum from radio up to very high energy gamma-rays can serve as a test of the particle acceleration and touches on one of the unresolved problems of modern astrophysics, namely the origin of cosmic rays and the Galaxy's contribution to the overall cosmic ray spectrum. The multiwavelength observations of Cas A SNR demonstrated that structure and spectral features have clear signs of young SNRs and its overall properties make this object the best target to test a hypothesis of cosmic ray origin in SNRs. Studies of Cas A at very high energies by SHALON telescope showed the location of TeV gamma-ray emission region relative to the position of reveres shock. Also, the spectral energy distribution was obtained at high and very high energies. To describe the spectral and structural features of this SNR viewed in non-thermal emission, two approaches involving reverse and also both reverse and forward shocks to the mechanism of diffusive shock acceleration of cosmic rays in Cas A were applied. It is demonstrated that the observational properties of Cas A are well reproduced by the hadronic model with significant contribution of both the forward and reverse shocks in the generation of broadband emission. Calculation results suggest that the very high efficiency of particle acceleration in Cas A, which value is up to 25% of the supernova explosion energy with energy of accelerated particles not exceeding of
5.
Starting with the hypothesis that cosmic rays are evenly distributed in the metagalaxy, it is shown that the flux of the electron-positron component, which is produced through --e decays, following the nuclear collisions of the cosmic ray beam with the intergalactic medium, takes <-4×1016 sec to reach steady state. The corresponding value of the flux of thepositron component and its implications regarding the homogeneous model of the metagalactic origin of cosmic rays are discussed.On leave from Tata Institute of Fundamental Research, Bombay, India. 相似文献
6.
The cosmic ray 11-year variation for solar cycle 20 is attributed to the modulating effect of solar flare-induced shocks propagating through the interplanetary medium to the boundary of the heliosphere. The relative influence of these disturbances upon the cosmic ray intensity as a function of their travel time from the Sun is determined by a deconvolution of a linear system with the number of solar flares (importance 1) and the observed cosmic ray intensity as the input and output respectively of this system. The impulse response function so determined indicates that the solar flare - induced disturbances significantly modulate cosmic rays out to a distance of 70–90 AU where the modulating effect of the disturbances abruptly ends. This is interpreted as the boundary of the heliosphere. 相似文献
7.
The affected pixel number distribution of the ISOCAM Long-Wave (LW) detector in cosmic ray-induced glitchesis calculated. The methods employed are Monte Carlo ray-tracing techniques and the taxi metric, which allows direct calculation of the affected pixels based on the knowledge of entry and exit points of the ray. The simulation results are compared with long-term experimental data. Based on the simulations combined with the CREME96 cosmic ray model for solar quiet period, it is estimated that the detector is on average traversed by 0.3 cosmic ray protons per second. For the experimental data, a corresponding minimum bound of 0.14 cosmic ray protons per second is obtained. Deviations in the simulated and measured pixel number distributions are discussed. 相似文献
9.
K. N. Yu 《Astrophysics and Space Science》1987,135(2):291-300
The baryon-symmetric domain cosmology (BSDC) of Steckeret al. (1971) have explained the diffuse -ray background. However, evidence has shown that active galactic nuclei (AGNs) are likely contributors to the diffuse -ray background, so there are some problems with the original formulations. We have reviewed the original formulations and have modified the expressions for the matter temperature and the redshifts at which the cosmic radiation from the BSDC becomes significantly absorbed. In this way, we show that the cosmic radiation from the BSDC agrees remarkably with the cosmic X-ray background from 1 keV to 100 keV. We have also shown that AGNs contribute significantly to the cosmic background beyond 100 keV. Therefore, we have arrived at a consistent model in which the BSDC model and AGN model together can explain the cosmic background from 1 keV to 1 MeV. 相似文献
10.
S. T. Lindgren 《Solar physics》1968,5(3):382-409
McMath plage region 8818 passed over the visible solar disk on May 17–31, 1967. It was very active from its first appearance on the Eastern limb, several times producing bright optical flares and hard X-ray emission, accompanied by intense type II, type IV and centimeter radio bursts. Nevertheless, no solar particles could be detected near the earth until the evening of May 23, when three bright flares were observed in close succession at 25°–28° E. During the following build-up of the solar particle flux over 36 hours, the galactic cosmic ray flux > 1 GeV decreased gradually by about 5%. The flux of solar particles decreased in two steps on May 25, both accompanied by decreases in the equatorial geomagnetic field. These field depressions are attributed to storm plasma ejected from the parent flare of the May 23 particle event. The propagation of solar particles from May 23 on thus appears to be strongly affected by storm plasma from the parent flare of the May 23 event, without any indications of solar particles being trapped in that plasma.A later particle event early on May 28 was also associated with a bright flare in McMath region 8818, at 33° W. This event displayed a rapid build-up, with electrons arriving first, and an exponential decay. A smooth proton peak, 20 min wide, was detected on May 30 closely associated with an SSC attributed to plasma ejection from the parent flare of the May 28 event.Between the geomagnetic storms beginning on May 25 and May 30 an anomalous daily variation was observed in the cosmic ray flux >1 GeV, the time of maximum falling 7–10 hours earlier than normal. Storm time increases in the flux of galactic cosmic rays were seen on May 26 when the equatorial geomagnetic field was depressed by more than 400 . Low latitude auroras were also observed during that time.On leave from the University of Uppsala, Sweden. 相似文献
11.
At sufficiently low energies, cosmic ray protons capture electrons from interstellar Hi and become neutral. In the subsequent cascade to the ground state a Doppler-shifted Ly- photon may be emitted. The neutral cosmic ray will be excited collisionally by further encounters with the ambient interstellar gas, emitting additional Doppler-shifted Ly- photons. We give the form of the cosmic ray spectrum down to 10 keV, assuming that there is no cosmic ray injection below 1 MeV. The neutral fraction is evaluated as a function of energy, and the diffuse ultraviolet flux is calculated. Comparison is made with observations in the range 1225–1340 Å. We conclude that far more stringent limits on the flux of subcosmic rays may be obtained by consideration of the heating and ionization of Hi regions. 相似文献
12.
Solar flares and the cosmic ray intensity 总被引：2，自引：0，他引：2
C. J. Hatton 《Solar physics》1980,66(1):159-165
The relationship between the cosmic ray intensity and solar activity during solar cycle 20 is discussed. A model is developed whereby it is possible to simulate the observed cosmic ray intensity from the observed number of solar flares of importance 1. This model leads to a radius for the modulation region of 60–70 AU. It is suggested that high speed solar streams also made a small contribution to the modulation of cosmic rays during solar cycle 20. 相似文献
13.
During the period of the IQSY, January 1964 through December 1965, the sun remained quiet, accelerating few energetic particles. There were many instances during the IQSY when lowenergy detectors on satellites and space probes registered small intensity increases. However, few of these events were associated with protons of energies exceeding 10 MeV. Moreover, the maximum intensities (E
p > 500 keV) were typically 1–8/cm2sec ster. Most of these events were below the threshold of riometer detection.The largest solar cosmic ray event observed in 1964 by polar-based riometers was that of March 16. This event was observed by 30 and 50 Mc/s riometers at McMurdo Sound, Antarctica, and Shepherd Bay, N.W.T., Canada.The largest event in 1965 occurred on February 5 and was the largest during the IQSY. It was associated with a class 2 flare at about 1750 UT, February 5. The propagation time between the sun and Earth was about one hour. This event was well observed by satellites, space probes, and riometers.This paper discusses primarily the 5 February 1965 event. Some discussion is also given to the 16 March 1964 event, other small events during the IQSY, and the recent event in March 1966. 相似文献
15.
A study of the properties of the cosmic radiation of energy - 10 MeV generated by solar flares is reported. Data from four Pioneer spacecraft in interplanetary orbits, and separated by 180° in heliocentric longitude are employed. Attention is restricted to the properties evident at times in excess of 1 day after the occurrence of the parent flare. The anisotropic character of the radiation; the gradients in heliocentric longitude; the decay time constants; and the energy spectra of the radiation are all studied in detail.It is found that the equilibrium anisotropy assumes a direction - 45° E of the satellite-Sun line at very late times. It is suggested that the anisotropy at such times is parallel to E × B. This observation confirms that convection is the determining process in the escape of the solar cosmic rays from the solar system. It indicates that a positive radial gradient of solar cosmic radiation density has builtup at orbit of Earth some 4 days after a flare. This results in an effective convective velocity of approximately 1/2 the solar wind velocity. Direct measurements indicate the presence of strong gradients in heliocentric longitude even at very late times ( 4 days). These gradients are essentially invariant with respect to time, e-folding angles of n - 30° have been observed at - 10 MeV. The presence of these gradients has a major effect on the temporal variation of the cosmic ray flux during the decay phase of the flare effect. Thus, the observed decay time constant is either increased or decreased relative to the convective value depending on the position of the observer relative to the centroid of the cosmic ray population injected by the flare. The effect of the gradient becomes more pronounced at lower energies, and may even exceed the convective removal rate. The observed decay time constant, the characteristics of the anisotropy, and the gradient in longitude are shown to be inter-related as demanded by theory. It is shown that the exponent of the cosmic ray spectrum is dependent on the location of the observer relative to the centroid of the cosmic ray population injected by the parent flare. At a given point in the frame of reference of the cosmic ray population, the spectral exponent is invariant with time.Now at CSIRO, G.P.O. Box 124, Port Melbourne, Victoria 3207, Australia.On leave from Physical Research Laboratory, Ahmedabad, India. 相似文献
16.
We have measured excesses of Pd, Rh, Ru, REE, Co, Sr, and Y in a peat column from the Northern peat bog of the 1908 Tunguska explosion site. Earlier, in this peat column the presence of an Ir anomaly at the event layers (30- depth) has been found (Planet Space Sci. 48 (1998) 179). In these layers, Pd, Rh, Ru, Co, Sr, and Y show pronounced anomalies of a factor 4-7 higher than the background value. In the event layers there are also good correlations between the siderophile platinum group elements (Pd, Rh, Ru) and Co, indicators of cosmic material, which imply they might have the same source, i.e. the Tunguska explosive body. The patterns of CI-chondrite-normalized REE in the event layers are much flatter than those in normal peat layers and different from those in the nearby traps. Furthermore, in these layers the patterns of CI-chondrite-normalized PGEs and the element ratios (e.g. C/Pd, C/Rh, and between some siderophile elements) give evidence that the Tunguska explosive body was more likely a comet, although we cannot exclude the possibility that the impactor could be a carbonaceous asteroid. We have estimated the total mass of a solid component of the explosive body up to 103-106 tons. 相似文献
17.
The origin of the elements from Cu to As in the UH (ultra-heavy) cosmic rays is investigated and related to current concepts of the nucleosynthesis of solar system material. The charge spectrum of the UH cosmic rays in the interval 29Z60 is studied via a fully developed propagation calculation for source abundances given by solar system material, ther-process, the massive-star core helium-burnings-process, and explosive carbon burning. None of these sources considered individually can explain the cosmic ray observations. However a combination of material produced in ther-process, the core helium-burnings-process and in explosive carbon burning provides a good representation of the experimental data. The cosmic-rayr-process is found to differ from solar systemr-process events by an underproduction of the low-massr-process peaks relative to theA195 peak. The large cosmicray abundance forZ=40–44 may be due to anr-process fission component, but this explanation is by no means certain. Improved cosmic-ray data, especially for Zn–Sr, can provide limits to the various source contributions. The model described here gives a consistent picture for the origin of both the cosmic rays and the solar system elements just beyond iron, and adds additional evidence for the importance of massive stars as a site of nucleosynthesis and the birthplace of the cosmic rays.Enrico Fermi Institute. 相似文献
18.
G. A. Gurzadyan 《Astrophysics and Space Science》1985,113(2):213-231
A concept of stellar aggregate activity is advanced. It is shown that the aggregate activity is too high in order to generate cosmic rays. Two conditions lay claim to cosmic ray primary sources: (i) a very large number of sources (104), and (ii) a homogeneous distribution of sources in the Galaxy. Supernovae do not satisfy both those conditions, but stellar aggregates do. The total interstellar medium of the aggregate identifies with a supernova remnant and possesses properties favourable for the acceleration of cosmic rays up to a high energy by statistical mechanisms. The direct suppliers of primary cosmic rays are the flare stars in the aggregates. From the point of view of energetic resources as well as the energetic consistency of cosmic rays, aggregates are equivalent with supernova remmants. The aggregate must also be the source of gamma-rays. The usual UV Cet-type flare stars in the Sun's neighbourhood do not play any role as sources of primary cosmic rays.The aggregate conception connects the very fact of the existence of cosmic rays with the continued star-formation process in Galaxy. 相似文献
19.
20.
R. M. Muradian 《Astrophysics and Space Science》1980,69(2):339-351
The relationship between mass and angular momentum for the known cosmic objects has been examined, and it is shown that they are described by the generalized Regge-like dependence of the formJ=(m/m
p)1+1/n
wheren=2 for galaxies, their clusters and superclusters, andn=3 for asteroids, planets and stars. It offers the possibility, that Ambartsumian's superdense proto-matter has hadronic nature. This allows us to give a realistic and quantitave explanation with a minimum number of arbitrary assumptions for the origin of cosmic angular momenta, cosmic magnetic fields and offers the framework for other cosmogonic implications. This approach incorporates in a natural way the fundamental quantum-mechanical parameters andm
p, besides the classical parametersG andc, and allows us to derive simple expressions for masses and spins of cosmic objects through fundamental constants, some of which coincide with Eddington-Dirac's Large Number relations. 相似文献