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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.

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NASA NTRS2004

Nuclear Physics in Space: What We Can Learn From Cosmic Rays

Studies and discoveries in cosmic-ray physics and generally in Astrophysics provide a fertile ground for research in many areas of Particle Physics and Cosmology, such as the search for dark matter, antimatter, new particles, and exotic physics, studies of the nucleosynthesis, origin of Galactic and extragalactic gamma-ray diffuse emission, formation of the large scale structure of the universe etc. In several years new missions are planned for cosmic-ray experiments, which will tremendously increase the quality and accuracy of cosmic-ray data. On the other hand, direct measurements of cosmic rays are possible in only one location on the outskirts of the Milky Way galaxy and present only a snapshot of very dynamic processes. It has been recently realized that direct information about the fluxes and spectra of cosmic rays in distant locations is provided by the Galactic diffuse gamma-rays, therefore, complementing the local cosmic-ray studies. A wealth of information is also contained in the isotopic abundances of cosmic rays, therefore, accurate evaluation of the isotopic production cross sections is of primary importance for Astrophysics of cosmic rays, studies of the galactic chemical evolution, and Cosmology. In this talk, I will show new results obtained with GALPROP, the most advanced numerical model for cosmic-ray propagation, which includes in a self-consistent way all cosmic-ray species (stable and long-lived radioactive isotopes from H to Ni, antiprotons, positrons and electrons, gamma rays and synchrotron radiation), and all relevant processes and reactions.

Moskalenko, Igor V.↗
NASA NTRS1975

The isotopic composition of cosmic rays with 5 is less than or equal to z which is less than or equal to 26

Results obtained from a high altitude balloon flight from Thompson, Canada in August, 1973 are reported. The instrument consisted of a spark chamber, a Lucite Gerenkov counter and thirteen layers of scintillators. For heavy particles the Cerenkov-range method of analysis was used to determine the mass of particles energetic enough to produce a Cerenkov signal and then stop in the layered scintillators. The data appear to be consistent with current cosmic-ray propagation models. Using a simple exponential path length propagation model this data is extrapolated to the cosmic-ray source and some implications of the data are discussed as to the nature of the source.

Fisher, A. J.↗
NASA NTRS1975

Mirroring in the Fokker-Planck coefficient for cosmic-ray pitch-angle scattering in homogeneous magnetic turbulence

The Fokker-Planck coefficient for pitch-angle scattering, appropriate for cosmic rays in homogeneous stationary magnetic turbulence is computed without making any specific assumptions concerning the statistical symmetries of the random field. The Fokker-Planck coefficient obtained can be used to compute the parallel diffusion coefficient for high-energy cosmic rays propagating in the presence of strong turbulence, or for low-energy cosmic rays in the presence of weak turbulence. Because of the generality of magnetic turbulence allowed for in the analysis, special interplanetary magnetic field features, such as discontinuities or particular wave modes, can be included rigorously.

Goldstein, M. L.↗
NASA NTRS1997

The Systematic Interpretation of Cosmic Ray Data (The Transport Project)

The Transport project's primary goals were to: (1) Provide measurements of critical fragmentation cross sections; (2) Study the cross section systematics; (3) Improve the galactic cosmic ray propagation methodology; and (4) Use the new cross section measurements to improve the interpretation of cosmic ray data. To accomplish these goals a collaboration was formed consisting of researchers in the US at Louisiana State University (LSU), Lawrence Berkeley Laboratory (LBL), Goddard Space Flight Center (GSFC), the University of Minnesota (UM), New Mexico State University (NMSU), in France at the Centre d'Etudes de Saclay and in Italy at the Universita di Catania. The US institutions, lead by LSU, were responsible for measuring new cross sections using the LBL HISS facility, analysis of these measurements and their application to interpreting cosmic ray data. France developed a liquid hydrogen target that was used in the HISS experiment and participated in the data interpretation. Italy developed a Multifunctional Neutron Spectrometer (MUFFINS) for the HISS runs to measure the energy spectra, angular distributions and multiplicities of neutrons emitted during the high energy interactions. The Transport Project was originally proposed to NASA during Summer, 1988 and funding began January, 1989. Transport was renewed twice (1991, 1994) and finally concluded at LSU on September, 30, 1997. During the more than 8 years of effort we had two major experiment runs at LBL, obtained data on the interaction of twenty different beams with a liquid hydrogen target, completed the analysis of fifteen of these datasets obtaining 590 new cross section measurements, published nine journal articles as well as eighteen conference proceedings papers, and presented more than thirty conference talks.

Guzik, T. Gregory↗
NASA NTRS1988

Cosmic-ray lifetime in the Galaxy - Experimental results and models

The separation of the cosmic-ray Be isotopes achieved by two satellite experiments is discussed. From the measured isotopic ratio between the radioactive Be-10 (half-life = 1,500,000 years) and the stable Be-9, it is deduced that the cosmic rays propagate through matter with an average density of 0.24 = or - 0.07 atoms/ cu cm. The implications of this result for the cosmic-ray age is reviewed in the context of two models of confinement and propagation: the homogeneous model, normally identified with confinement ot the galactic gaseous disk, and a diffusion model in which the cosmic rays extend into a galactic halo. A newly deduced cosmic-ray pathlength distribution, a self-consistent model of solar modulation, and a set of fragmentation cross sections are calculated. It is concluded that in a homogeneous model, the cosmic-ray age is 15 (+7, -4) million years, about a factor longer than early estimates based on the abundances of the light nuclei Li, Be, and B and a nominal interstellar density of 1 atom/ cu cm.

Simpson, J. A.↗
NASA NTRS1984

Propagation of heavy cosmic-ray nuclei

Techniques for modeling the propagation of heavy cosmic-ray nuclei, and the required atomic and nuclear data, are assembled in this paper. Emphasis is on understanding nuclear composition in the charge range Z = 3-83. Details of the application of 'matrix methods' above a few hundred MeV/nucleon, a new treatment of electron capture decay, and a new table of cosmic ray-stable isotopes are presented. Computation of nuclear fragmentation cross sections, stopping power, and electron stripping and attachment are briefly reviewed.

Letaw, J. R.↗
NASA NTRS1974

Physics of solar cosmic rays

A review of the historical development of solar cosmic ray research is presented and details concerning the solar atmosphere, the interplanetary space, and solar activity are considered, giving attention to solar-atmosphere structure, problems of radiative transfer, questions of solar magnetism, solar wind, and interplanetary plasmas. Solar flares and associated phenomena are discussed along with the generation of solar cosmic ray events, the mechanism of solar flares, the acceleration process of solar cosmic rays, the propagation of solar cosmic rays, and relations between the flow of energetic protons and solar active regions. Questions regarding the origin theory of cosmic rays are also explored, taking into account the solar origin theory and problems of flare stars.

Sakurai, K.↗
NASA NTRS1979

Evidence for the deficiency of short cosmic ray pathlengths and a physically realistic explanation - The no-near-sources model

Recent observations of the charge and energy spectra of cosmic-ray nuclei are used to construct secondary-to-primary charge ratios at the two ends of the charge spectrum. These ratios are found to be inconsistent with the ad hoc leaky-box model of cosmic-ray propagation which leads to an exponential pathlength distribution. Models for which the pathlength distribution function is deficient in short pathlengths provide a more consistent picture. Several of these models, both ad hoc and physical, are investigated. The physical model considered is one for which detailed galactic propagation parameters and boundary conditions are used and for which there exist no near sources of cosmic rays over a time interval corresponding to a few times the cosmic-ray age.

Lezniak, J. A.↗
NASA NTRS1987

On the possibility of observing cosmic ray sources in high energy gamma rays

If cosmic rays are accelerated by strong shocks, then cosmic ray sources should be characterized by spectra, dN/dE alpha E exp -(2.0-2.2), reflecting the strength of those shocks. This is expected from the 'standard leaky box' model of cosmic ray propagation in which the source spectra are harder than the observed spectra because higher energy particles have shorter residence times in the galactic magnetic fields. Furthermore, data on cosmic ray nucleons suggest that these sources might be surrounded by material. If the latter is true, such sources should be observable in gamma rays at energies beyond 1 GeV where the angular resolution of gamma-ray telescopes is optimized and the background is significantly reduced. For identified sources, the source location accuracy can be shown to improve with increasing energy in spite of the decreasing statistics, as long as the gamma-ray spectrum is harder than dN/dE alpha E exp -gamma. A Monte Carlo model is used to predict the photon spectra which would be expected from cosmic ray sources under varying assumptions about the strength of the shocks in the acceleration region.

Ormes, J. F.↗
NASA NTRS1977

Consequences of using nonlinear particle trajectories to compute spatial diffusion coefficients

In a study of cosmic ray propagation in interstellar and interplanetary space, a perturbed orbit resonant scattering theory for pitch angle diffusion in a slab model of magnetostatic turbulence is slightly generalized and used to compute the diffusion coefficient for spatial propagation parallel to the mean magnetic field. This diffusion coefficient has been useful for describing the solar modulation of the galactic cosmic rays, and for explaining the diffusive phase in solar flares in which the initial anisotropy of the particle distribution decays to isotropy.

Goldstein, M. L.↗