Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “cosmic ray sources”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

The (C-13)/(C-12) ratio in cosmic ray sources

Published measurement data on the production C-13 during interstellar propagation of cosmic rays (Webber et al., 1987; Guzik et al., 1985) are combined with observational data to determine the relative abundance of C-13 in the cosmic-ray source. The theoretical basis and implementation of the calculations are described in detail, and the results are presented in graphs. (C-13)/(C-12) is estimated as 0.003 + or - 0.005, consistent with the solar ratio (0.011), not consistent with the local abundance ratio (0.023), and in agreement with the source ratio predicted by Prantzos et al. (1985) using the isotopic abundances of WR-star ejecta.

Webber, W. R.↗
NASA NTRS1988

On the high-energy gamma-ray signature of cosmic-ray sources

Monte Carlo simulations of the gamma-ray emission from hypothetical cosmic-ray sources are performed. Sources which might correspond to acceleration by supernova shocks in 'average' interstellar conditions and deep within giant molecular clouds are considered. The consequences of dropping the common assumption that the cosmic-ray spectrum at the sources is the same as that observed at earth are examined. Spectral effects which can be related to the depth of the material shroud and the population of accelerated particles are explored using these simulations and are described. The results are compared with the COS B catalog of gamma-ray sources, and the implications for the underlying particle populations and source mechanisms are discussed.

Ormes, J. F.↗
NASA NTRS2009

Insights into the Galactic Cosmic-ray Source from the TIGER Experiment

We report results from 50 days of data accumulated in two Antarctic flights of the Trans-Iron Galactic Element Recorder (TIGER). With a detector system composed of scintillators, Cherenkov detectors, and scintillating optical fibers, TIGER has a geometrical acceptance of 1.7 sq m sr and a charge resolution of 0.23 cu at Iron. TIGER has obtained abundance measurements of some of the rare galactic cosmic rays heavier than iron, including Zn, Ga, Ge, Se, and Sr, as well as the more abundant lighter elements (down to Si). The heavy elements have long been recognized as important probes of the nature of the galactic cosmic-ray source and accelerator. After accounting for fragmentation of cosmic-ray nuclei as they propagate through the Galaxy and the atmosphere above the detector system, the TIGER source abundances are consistent with a source that is a mixture of about 20% ejecta from massive stars and 80% interstellar medium with solar system composition. This result supports a model of cosmic-ray origin in OB associations previously inferred from ACE-CRIS data of more abundant lighter elements. These TIGER data also support a cosmic-ray acceleration model in which elements present in interstellar grains are accelerated preferentially compared with those found in interstellar gas.

Link, Jason T.↗
NASA NTRS2003

Refractory nuclides in the cosmic-ray source

New observations of the abundances and energy spectra of the isotopes of Mg, Al, and Si from ACE/CRIS are used to extend our previous results on the composition of refractory nuclides in cosmic-ray source material.

cosmic rays composition heavy nuclei↗
NASA NTRS1985

Implications of new measurements of O-16 + p + C-12,13, N-14,15 for the abundances of C, N isotopes at the cosmic ray source

The fragmentation of a 225 MeV/n O-16 beam was investigated at the Bevalac. Preliminary cross sections for mass = 13, 14, 15 fragments are used to constrain the nuclear excitation functions employed in galactic propagation calculations. Comparison to cosmic ray isotonic data at low energies shows that in the cosmic ray source C-13/C approximately 2% and N-14/0=3-6%. No source abundance of N-15 is required with the current experimental results.

Guzik, T. G.↗
NASA NTRS1981

Implications of ultraheavy cosmic-ray source composition derived from observations by the HEAO-3 heavy nuclei experiment

The contribution of r-process and s-process nucleosynthesis to the Cameron (1980) solar system (SS) abundances for Z at least 33 has been derived. In the interval Z equals 34-40 HEAO-3 data extrapolated to the cosmic-ray source (CRS) fit the solar system mix better than r-process. In the interval Z between 26-40 the HEAO-3 results for CRS/SS follow the same general correlation with first ionization potential as for the lighter elements although there are deviations in detail.

Israel, M. H.↗
NASA NTRS1985

Virgo cluster as a high energy cosmic rays source

The extragalactic charged particles are reflecting from the Galaxy by its magnetic field. Assuming magnetic field in the Galaxy as quasilongitudinal, the mean transparency of Galaxy has been evaluated for extragalactic protons defined as a fraction of particles at a given energy from a given direction passing by the galactic plane. The anisotropy caused by the Galactic magnetic field reflection of protons can explain observed arrival directions of extensive air showers at large angle to the galactic plane. Our analysis shows that the increase with energy observed in sin b sup 11 is self-consistent with changing in the cosmic ray energy spectrum at high energy (E 10 to the 19th power eV) in the case when extragalactic cosmic ray source with spectral index -2.2 is at the position of the Virgo Cluster.

Karakula, S.↗
NASA NTRS1973

Cosmic ray sources - Evidence for two acceleration mechanisms.

The difference between the energy spectra of iron and other cosmic rays is interpreted in terms of two source mechanisms. One mechanism, possibly acceleration at neutron star surfaces, produces the iron, and another is responsible for the rest of the primary nuclei. Within this model, observations of high-energy cosmic rays could determine whether secondary nuclei are produced in the sources or in the interstellar medium.

Ramaty, R.↗
NASA NTRS1972

Cosmic ray sources: Evidence for two acceleration mechanisms

The difference between the spectra of iron and other cosmic rays is interpreted in terms of two source mechanisms. One mechanism, possibly acceleration at neutron star surfaces, produces the iron and another is responsible for the rest of the primary nuclei. Within this model, high energy observations could determine whether secondary nuclei are produced in the sources or in the interstellar medium.

Ramaty, R.↗
NASA NTRS1986

Cosmic ray sources, acceleration and propagation

A review is given of selected papers on the theory of cosmic ray (CR) propagation and acceleration. The high isotropy and a comparatively large age of galactic CR are explained by the effective interaction of relativistic particles with random and regular electromagnetic fields in interstellar medium. The kinetic theory of CR propagation in the Galaxy is formulated similarly to the elaborate theory of CR propagation in heliosphere. The substantial difference between these theories is explained by the necessity to take into account in some cases the collective effects due to a rather high density of relativisitc particles. In particular, the kinetic CR stream instability and the hydrodynamic Parker instability is studied. The interaction of relativistic particles with an ensemble of given weak random magnetic fields is calculated by perturbation theory. The theory of CR transfer is considered to be basically completed for this case. The main problem consists in poor information about the structure of the regular and the random galactic magnetic fields. An account is given of CR transfer in a turbulent medium.

Ptuskin, V. S.↗
NASA NTRS1972

Cosmic-ray source and local interstellar spectra deduced from the isotopes of hydrogen and helium.

A self-consistent model for cosmic-ray hydrogen and helium propagation from the sources in the Galaxy to the orbit of earth is obtained, taking into account experimental information now available on the isotopes H-1, H-2, He-3, and He-4. The only adjustable parameters include the shape of the energy spectra of H-1 and He-4 at the time of source injection, the distribution of particle path lengths in interstellar space, and the solar modulation parameters. It is found that the allowed form of the source differential spectra of the H-1 and He-4 nuclei is dominated by a power law in total energy.

Comstock, G. M.↗
NASA NTRS1983

Adiabatic expansion of cosmic ray sources and the consequences for secondary antiprotons

The low-energy antiproton flux measurement of Buffinton et al. (1981) is more than an order of magnitude higher than can be explained by interstellar production. It has been suggested that the excess antiprotons may be created by supernovae in very dense regions of ISM. These sources would provide the additional target material necessary to produce the excess cosmic ray antiprotons; in addition, adiabatic energy losses due to supernova expansion will increase the flux of low-energy antiprotons. The antiproton flux from such sources is examined here, with attention given to the energy loss effects of the adiabatic and collisional losses of both the primary and secondary cosmic ray fluxes. Ionization losses of the antiprotons are also considered.

Mauger, B. G.↗
NASA NTRS1972

The survival of heavy nuclei in cosmic ray source environments

Results from the Goddard balloon spectrometer and the results reported by Soviet scientists using the Proton series of satellites are summarized. The important experimental results from the balloon spectrometer experiment are as follows: (1) On a total-energy scale, protons constitute only a minor proportion of the cosmic rays, only 20 percent. The rest of the cosmic rays are complex nuclei. (2) All the nuclei have the same power low spectrum in total energy and so the composition seems to be independent of energy.

Balasubrahmanyan, V. K.↗
NASA NTRS1985

The model-independence of cosmic ray source determinations

The direct inversion method of Margolis is used to explore the dependence of Z less than or equal to 28 source abundance determinations on the choice of the pathlength distribution. The source abundances do not depend strongly on the form of the truncation used, although some truncation at the lower energies (compared to a leaky box) is necessary. The decrease of mean grammage with increasing energy is required by the observations. The effects of errors and he use of other secondary to primary ratios is discussed.

Margolis, S. H.↗