Cosmic-ray Abundances Research Articles

The cosmic-ray source composition

The cosmic-ray source composition is shown to be related to the observed cosmic-ray abundances by a set of linear equations which are valid for either ad hoc path length distributions or quantitative solutions of galactic propagation models. In the limit of no ionization energy loss, this method is exact for all path length distributions and can replace more detailed numerical integrations; it provides a simple way to calculate directly the source composition implied by a particular set of cross sections, observed abundances, and propagation model. This method is used to determine the source abundances of the galactic cosmic rays in a model-independent manner. Compared to a simple exponential, the path length distribution required by observations is deficient in the contributions from short (not greater than 0.5 g/sq cm) paths at energies of a few GeV per nucleon.

Track kinetics of volume tracks in crystals

The extraterrestrial crystals provide us valuable exposed samples to study Ultra Heavy (UH) cosmic rays. Beside UH cosmic ray abundances, these studies can provide information regarding cosmic ray source history. The observed low abundances of actinides in HEAO-3 and ARIEL-VI UH cosmic ray experiments, have increased the importance of these studies. The total etchable track length is used for track identification in crystals. However lack of direct calibration to UH nuclei and proper kinetics for volume tracks are the major disadvantages of such studies. Fortunately, in the recent past, these crystals are calibrated to accelerated Uranium beam. In this paper, we describe track kinetics for volume tracks on the basis of track etch rate data for Uranium tracks. We have used the simple approach of single etchant passage to reveal the volume tracks and the variation of VETL is studied using track profiles from computer. The optimum conditions and possible charge resolution are considered from this analysis.

Prospects for Cosmic Dust Experiments on the Planned Reflight of LDEF

AbstractThe Long Duration Exposure Facility (LDEF-I), which contains a number of cosmic dust experiments, is due to be launched in the spring of 1984 and recovered about a year later. Current plans call for re-fitting the LDEF spacecraft with a large area of plastic nuclear track detectors and relaunching (LDEF-II) for a flight that will last about 2 years. The main purpose of the mission is to extend primary cosmic ray abundance measurements to the actinide region. A meeting was held at Washington University in December 1983 to discuss the problems and prospects for cosmic dust experiments on LDEF-II. Most participants were drawn from the LDEF-I community of investigators. The meeting resulted in a report which treated the scientific rationale for LDEF-II dust experiments, discussed various implementation options, and concluded with a set of summary recommendations. We discussed this report and summarized the status of LDEF-II as of this meeting. It is important to note that the report serves equally well as a basis for discussion of dust experiments on future space stations.

Clues from the photonuclear time scale on the nature of particle accelerators in Cygnus X-3 and Vela X-1

Ultrahigh-energy γ rays (≳ 1015eV) have recently been observed from the binary X-ray sources Cygnus X-3 and Vela X-1. The source of these γ rays remains unknown but it seems likely that protons or nuclei are accelerated, the γ rays resulting from nuclear interactions with matter or radiation. Objects of this type could then contribute significantly to the observed cosmic radiation. The maximum proton energy that can be achieved (this may determine the maximum γ-ray energy) occurs when the acceleration time scale becomes greater than the energy loss time scale, that is, the attenuation time. Here we have calculated the attenuation times of protons and heavier nuclei in the radiation fields of the stellar companions to the Cyg X-3 and Vela X-1 compact objects. The maximum observed γ-ray energy enables us to put an upper limit on the acceleration time scale of protons at 3×1016 eV of 104−3 × 105 s for Cyg X-3 and 105 s for Vela X-1. This result can be used to put some constraints on the nature of the particle accelerator. If binary X-ray sources are contributing significantly to the cosmic rays, the cosmic-ray abundances will be affected by photonuclear interactions.

Derivation of cosmic-ray source abundances above 10 GeV per nucleon and implications for air-shower measurements

The form of the energy spectra and the composition of cosmic rays on acceleration are important for illuminating the important question of the origin of cosmic rays at air-shower energies, a subject of considerable current interest following the recent detection of ultra-high-energy gamma rays from Cyg X-3 and Vela X-1. Source abundances of cosmic rays are usually calculated from data below approximately 1 GeV per nucleon and may not be applicable to air-shower energies. In this Letter, recent measurements of the energy spectra of cosmic-ray hydrogen, helium, oxygen and iron to energies greater than 104 GeV per nucleus are used, together with a recent determination of the mean escape length of cosmic rays from the galaxy, to obtain the energy spectra and composition of these components on acceleration. The source spectra at these energies are consistent with power laws in rigidity with exponents of -2.0, as expected for acceleration by strong shocks and also as inferred for acceleration in binary X-ray sources.

On the abundances of ultraheavy cosmic rays

Recent data from the HEAO 3 and Ariel 6 satellites on elemental abundances of ultraheavy cosmic rays (33< or =Z< or =83) are analyzed using a new propagation code. General agreement with earlier analyses is observed. Evidence for a breakdown of the correlation between ionization potentials and the solar system/cosmic-ray source abundance ratio is presented. We find that the best fit to experimental data (approx.5 GeV per nucleon) occurs when propagation is calculated at lower energies (approx.1 GeV per nucleon). This is interpreted as evidence for distributed acceleration of cosmic rays. Additional effects, including ionization loss, altered path-length distributions, and r-process enhancement, are considered.

Elemental abundances of ultraheavy cosmic rays

The elemental composition of the cosmic-ray source is different from that which has been generally taken as the composition of the solar system. No general enrichment of products of either r-process or s-process nucleosynthesis accounts for the differences over the entire range of ultraheavy (Z > 30) elements; specific determination of nucleosynthetic contributions to the differences depends upon an understanding of the nature of any acceleration fractionation. Comparison between the cosmic-ray source abundances and the abundances of C1 and C2 chondritic meteorites suggests the possibility that differences between the cosmic-ray source and the “standard (C1) solar system” may not be due to acceleration fractionation of the cosmic rays, but may be due instead to a fractionation of the C1 abundances with respect to the interstellar abundances.

Implioations of HEAO 3 data for the acceleration and propagation of galactic cosmic rays

The energy dependence of the mean escape length of cosmic rays from the galaxy in the light of recent measurements of cosmic ray abundances from the Danish-French experiment on HEAO-3 is re-examined. The energy dependence is found to be steeper than previously thought.

Cosmic-ray abundances of Sn, Te, Xe, and BA nuclei measured on HEAO 3

Elements with even atomic number ( Z) in the interval 50 ~ Z ~ 56 have been resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO 3 satellite. The observation that 50Sn and 56Ba are more abundant than 52Te Elements with even atomic number ( Z) in the interval 50 ~ Z ~ 56 have been resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO 3 satellite. The observation that 50Sn and 56Ba are more abundant than 52Te and 54Xe is inconsistent with a purer-process cosmic-ray source. Adjustment of source abundances for an enhancement of those elements with a low first ionization potential does not change this conclusion and 54Xe is inconsistent with a purer-process cosmic-ray source. Adjustment of source abundances for an enhancement of those elements with a low first ionization potential does not change this conclusion.

Charge abundance of cosmic rays at their source

view Abstract Citations (22) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Charge abundance of cosmic rays at their source Webber, W. R. Abstract The relative charge abundance of galactic cosmic-ray nuclei is measured between 600 and 1000 MeV per nucleon over a range of Z from 2 to 28. The abundances observed at earth are extrapolated to the cosmic-ray source, yielding accurate source abundances for 15 elements. These abundances, together with recently measured isotopic abundance ratios, are compared with the average abundances observed in another sample of accelerated material - solar cosmic rays. Appreciable differences are found in the composition for the elements He, C, N, and Ne. The galactic and solar cosmic-ray abundances are also compared with a variety of compilations of unaccelerated matter. Publication: The Astrophysical Journal Pub Date: April 1982 DOI: 10.1086/159834 Bibcode: 1982ApJ...255..329W Keywords: Abundance; Charged Particles; Cosmic Rays; Nuclear Fusion; Nucleons; Particle Acceleration; Cerenkov Counters; Chemical Composition; Data Reduction; Galactic Radiation; Isotopes; Space Radiation full text sources ADS |

Indicators of nucleosynthesis and acceleration processes in the ultraheavy cosmic rays: Z not less than 24 and not greater than 59

The observable abundances of the ultraheavy cosmic rays in the charge range 24< or =Z< or =59 have been calculated using different source abundances hypotheses. These include the standard solar-system abundances, r-process--only abundanes, and these two sets modified by the first ionization potential of the elements to test for preferential acceleration effects. The propagated elemental abundance patterns that result are distinctive signatures of nucleosynthesis and acceleration. Present data seem to suggest solar-system abundances with a dependence upon the first ionization potential for the elements 30< or =Z< or =40.

A method for measuring the isotopic abundances of cosmic rays

ABSTRACT A method is described for measuring the isotopic composition of elements with Z ≥ 26 in cosmic rays, using plastic track detectors.

Cosmic-ray abundances of elements with atomic number 26 less than or equal to 40 measured on HEAO 3

view Abstract Citations (32) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Cosmic-ray abundances of elements with atomic number 26 less than or equal to 40 measured on HEAO 3 Binns, W. R. ; Fickle, R. K. ; Waddington, C. J. ; Garrard, T. L. ; Stone, E. C. ; Israel, M. H. ; Klarmann, J. Abstract Individual elements in the cosmic radiation of even atomic number (Z) in the interval 26-40 have been resolved and their relative abundances measured. The results are inconsistent with a cosmic-ray source whose composition in this charge interval is dominated by r-process nucleosynthesis. The ratios of cosmic-ray source abundances to solar system abundances in this interval follow the same general correlation with first ionization potential as for the lighter elements, although there are deviations in detail. Publication: The Astrophysical Journal Pub Date: August 1981 DOI: 10.1086/183602 Bibcode: 1981ApJ...247L.115B Keywords: Abundance; Cosmic Rays; Heao 3; Nuclear Fusion; Solar System; Ionization; Isotopes; Radiation Sources; Space Radiation full text sources ADS |

The HEAO-3 French-Danish cosmic ray spectrometer: Preliminary results on the elemental abundances of cosmic ray nuclei in the iron peak

The French-Danish cosmic ray spectrometer was launched on HEAO-3 on September 20, 1979. This instrument was optimized to measure the charge composition and isotopic abundances of galactic cosmic rays with energies of about 0.5 to 7 GeV/nucleon, using the multi-Cerenkov detector technique and a flash tube hodoscope. The geomagnetic method used for isotope analysis required the accurate measurement of the momentum of each observed particle. The technique used and the problems involved are illustrated using observed data. The high charge resolution of the instrument permits complete separation of all chemical elements between Be and Ni, even at energies larger than 5 GeV/nucleon. Preliminary results are presented for relative abundances of individual elements 21 ⩽ Z ⩽ 28.

Effects of statistical post-acceleration on nuclear abundances of cosmic rays

Effects of statistical post-acceleration on nuclear abundances of cosmic rays

Cosmic-ray abundances of individual elements in the Z interval between 26 and 30

The relative abundances of Fe, Co, Ni, Cu, and Zn in the cosmic rays have been measured using a large-area balloon-borne electronic detector system. The abundance ratios Ni/Fe and Zn/Fe are 5.0 + or - 0.2% and 0.06 + or - 0.01%, respectively. The Zn abundance is low (40%) compared with the Cameron (1973) (C1) solar system, and is best consistent with the solar system C2 meteorite abundances. The ratios Co/Fe and Cu/Fe, extrapolated to the top of the atmosphere, are 0.68 + or - 0.14% and 0.066 + or - 0.030% respectively; since charge peaks are not resolved at Co and Cu, these results are taken as upper limits of 0.8% and 0.1%, respectively. The Co upper limit is consistent with complete decay of Co-57 at the source and implies a lower limit of 2 years for the time between nucleosynthesis and acceleration of these nuclei.

Time delay between the nucleosynthesis of cosmic rays and their acceleration to relativistic energies

If cosmic rays originate in a supernova explosion, they might be accelerated immediately after their synthesis. This would prevent electron-capture decay of unstable isotopes, and could result in large differences between cosmic-ray and solar-system abundances. Existing data on the abundances of iron, cobalt, and nickel in cosmic rays show great similarity to the solar system abundances, therefore, it is concluded that more than a year elapses between the synthesis of the cosmic-ray nuclei and their acceleration to relativistic energies. 2 figures.

Is the cosmic ray source composition energy dependent at high energy?

Use has been made of the non-homogeneous diffusive model of cosmic ray propagation described by Le Guet and Pacheco (1973) and modified by Le Guet and Stanton (1974) to calculate the cosmic ray source composition at 50 GeV/n. It is assumed to be energy independent in order to predict the cosmic ray abundances at the top of the Earth's atmosphere for different energies in the range 2.5-50 GeV/n. The conclusion arrived at is that the assumption of constant source composition is consistent with the observations and the nuclear data presently available in the energy range considered.

UH cosmic rays and solar system material: The elements just beyond iron

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 29≤Z≤60 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 theA∼195 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.

Consistency of cosmic-ray composition, acceleration mechanism, and supernova models

view Abstract Citations (34) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Consistency of cosmic-ray composition, acceleration mechanism, and supernova models. Hainebach, K. L. ; Norman, E. B. ; Schramm, D. N. Abstract It is shown that a consistent picture of cosmic-ray composition can be obtained by synthesizing the observed cosmic-ray abundances with the acceleration mechanisms of Scott and Chevalier (1975) or Jokipii (1975), and the presupernova models of Arnett and Schramm (1973), with explosive processing. If this model is valid, then it is possible to estimate the location of the supernova 'mass cut', possible anomalies in the yet to be accurately observed cosmic-ray iron isotopic ratios, the cosmic-ray ratio of r- to s-process elements, and the time between the supernova explosion and the acceleration of the cosmic rays. Publication: The Astrophysical Journal Pub Date: January 1976 DOI: 10.1086/154073 Bibcode: 1976ApJ...203..245H Keywords: Abundance; Astronomical Models; Cosmic Rays; Particle Acceleration; Supernovae; Nuclear Fusion; Solar System; Stellar Evolution; Stellar Mass; Astrophysics full text sources ADS |