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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Galactic cosmic rays and anomalous components in the heliosphere

The progress made during 1983-1986 by U.S scientists on modulation of Galactic cosmic rays by the sun and on the origin, acceleration, and modulation of the anomalous components in the heliosphere is reviewed. In these years, simultaneous observations of modulation, covering a radial range from 1 to more than 30 AU and a heliospheric latitude range from 0 to greater than 20 deg, made it possible to investigate directly the dynamics and spatial scale of modulation during both the increasing and declining phases of solar activity and to make in situ correlations between changes in the interplanetary medium and changes in the modulation of cosmic rays. Particular attention is given to the use of the observations related to time-dependent modulation effects, curvature drifts, and anomalous components, as well as of the measurements of the cosmic-ray radial gradients and latitudinal intensity variations, in the modeling of solar modulation effects.

Mckibben, R. B.↗
NASA NTRS2007

Observations of the Li, Be, and B Isotopes and Constraints on Cosmic-ray Propagation

The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCR) between E=50-200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g. B/C, Li/C, etc) are also consistent with other GCR observations. A approx. 15-20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.

deNolfo, G. A.↗
DOE OSTI2012

CHEMICAL ANALYSIS OF A DIFFUSE CLOUD ALONG A LINE OF SIGHT TOWARD W51: MOLECULAR FRACTION AND COSMIC-RAY IONIZATION RATE

Absorption lines from the molecules OH{sup +}, H{sub 2}O{sup +}, and H{sup +} {sub 3} have been observed in a diffuse molecular cloud along a line of sight near W51 IRS2. We present the first chemical analysis that combines the information provided by all three of these species. Together, OH{sup +} and H{sub 2}O{sup +} are used to determine the molecular hydrogen fraction in the outskirts of the observed cloud, as well as the cosmic-ray ionization rate of atomic hydrogen. H{sup +} {sub 3} is used to infer the cosmic-ray ionization rate of H{sub 2} in the molecular interior of the cloud, which we find to be {zeta}{sub 2} = (4.8 {+-} 3.4) Multiplication-Sign 10{sup -16} s{sup -1}. Combining the results from all three species we find an efficiency factor-defined as the ratio of the formation rate of OH{sup +} to the cosmic-ray ionization rate of H-of {epsilon} = 0.07 {+-} 0.04, much lower than predicted by chemical models. This is an important step in the future use of OH{sup +} and H{sub 2}O{sup +} on their own as tracers of the cosmic-ray ionization rate.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

A cosmic ray super high multicore family event. 1: Experiment and general features

Information on the fragmentation region in super high energy hadronic interactions can be obtained through the observations of gamma-ray families produced by cosmic rays. Gamma-ray families with the sum of E sub gamma or 1000 TeV are receiving increasing interests in emulsion chamber experiments. There exist some complications caused by the superposition of nuclear and electromagnetic cascades and the uncertainty in the nature of the primary particles. These complications usually make the conclusions drawn from various interesting phenomena observed in family events not so definite. An interesting family event KO E19, which is likely to have suffered only very slight disturbances is described. It was found in the Mt. Kambala emulsion chamber experiment. The production height of the event is determined to be H=(70 + or - 30)m and some conclusions are given.

Ren, J. R.↗
NASA NTRS1977

Hydrostatic equilibrium of gas, extent of cosmic ray confinement, and radio emission in the Galaxy

A detailed study of the hydrostatic equilibrium of the gas-field system perpendicular to the galactic plane in the neighborhood of the sun, assuming that the magnetic field is parallel to the plane, has been carried out. It is found that the distribution of pressure due to cosmic rays and the magnetic field is different from that due to the gas. The observed radio spectrum in the direction of the galactic pole can be understood if one includes in the hydrostatic equilibrium the distribution of gas in the halo. The results of this analysis show that in the galactic plane, the cosmic-ray density is approximately 2 to 3 eV/cu cm with a magnetic-field strength of about 5 to 6 microgauss. It is inferred that cosmic rays are confined to a more extended volume in the Galaxy (with an equivalent thickness of at least 2 kpc in the solar neighborhood) than the gas disk, and the magnetic-field strength slowly decreases to a value of 1 microgauss only beyond about 5 kpc from the plane. Further, there is no evidence for a quasi-spherical radio halo, although the radio emission extends beyond the gas disk with scale height of at least 1 kpc. A lower limit of about 6 million years for the confinement of cosmic rays in the Galaxy has been set.

Badhwar, G. D.↗
NASA NTRS1981

The low-energy galactic cosmic ray carbon, nitrogen, and oxygen isotopic composition

It is found that C, N, and O elemental and isotopic ratios in the galactic cosmic rays measured near the earth with the IMP 7 telescope of the University of Chicago have had the values N/O = 0.25 + or 0.02; C/O = 1.06 + or - 0.03; C-13/C = 0.04-0.10; N-15/N = 0.47 + or - 0.06; and O-18/O less than or equal to 0.03. It is noted that these results are confirmed by IMP 8 measurements. The measurements are extrapolated back to the cosmic ray source using exponential and truncated exponential path length distributions whose parameters have been determined by fitting cosmic ray B/C and sub-Fe/Fe ratios measured previously.

Guzik, T. G.↗
DOE OSTI2014

Effects of turbulence on cosmic ray propagation in protostars and young star/disk systems

The magnetic fields associated with young stellar objects are expected to have an hour-glass geometry, i.e., the magnetic field lines are pinched as they thread the equatorial plane surrounding the forming star but merge smoothly onto a background field at large distances. With this field configuration, incoming cosmic rays experience both a funneling effect that acts to enhance the flux impinging on the circumstellar disk and a magnetic mirroring effect that acts to reduce that flux. To leading order, these effects nearly cancel out for simple underlying magnetic field structures. However, the environments surrounding young stellar objects are expected to be highly turbulent. This paper shows how the presence of magnetic field fluctuations affects the process of magnetic mirroring, and thereby changes the flux of cosmic rays striking circumstellar disks. Turbulence has two principle effects: (1) the (single) location of the magnetic mirror point found in the absence of turbulence is replaced with a wide distribution of values. (2) The median of the mirror point distribution moves outward for sufficiently large fluctuation amplitudes (roughly when δB/B {sub 0} > 0.2 at the location of the turbulence-free mirror point); the distribution becomes significantly non-Gaussian in this regime as well. These results may have significant consequences for the ionization fraction of the disk, which in turn dictates the efficiency with which disk material can accrete onto the central object. A similar reduction in cosmic ray flux can occur during the earlier protostellar stages; the decrease in ionization can help alleviate the magnetic braking problem that inhibits disk formation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

Cosmic-ray streaming and anisotropies

The paper is concerned with the differential current densities and anisotropies that exist in the interplanetary cosmic-ray gas, and in particular with a correct formulation and simple interpretation of the momentum equation that describes these on a local basis. Two examples of the use of this equation in the interpretation of previous data are given. It is demonstrated that in interplanetary space, the electric-field drifts and convective flow parallel to the magnetic field of cosmic-ray particles combine as a simple convective flow with the solar wind, and that there exist diffusive currents and transverse gradient drift currents. Thus direct reference to the interplanetary electric-field drifts is eliminated, and the study of steady-state and transient cosmic-ray anisotropies is both more systematic and simpler.

Forman, M. A.↗
DOE OSTI2018

A High-efficiency Cosmic Ray Veto Detector for the Mu2e Experiment

The Mu2e experiment at Fermilab will search for new physics through the observance of the neutrino-less decay of a muon to an electron in the presence of a nucleus. The experiment will have a single-event sensitivity of $3\times10^{-17}$, requiring an active cosmic-ray veto to keep background from cosmic rays to fewer than one event over the three year lifetime of the experiment. The Mu2e Cosmic Ray Veto (CRV) has been designed to have an efficiency of 99.99\%. The design and fabrication of the CRV will be discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1989

Computer simulations of cosmic-ray diffusion near supernova remnant shock waves

A plasma simulation model was used to study the resonant interactions between streaming cosmic-ray ions and a self-consistent spectrum of Alfven waves, such as might exist in the interstellar medium upstream of a supernova remnant shock wave. The computational model is a hybrid one, in which the background interstellar medium is an MHD fluid and the cosmic-rays are discrete kinetic particles. The particle sources for the electromagnetic fields are obtained by averaging over the fast cyclotron motions. When the perturbed magnetic field is larger than 10 percent of the background field, the macro- and microphysics are no longer correctly predicted by quasi-linear theory. The particles are trapped by the waves and show sharp jumps in their pitch-angles relative to the background magnetic field, and the effective ninety-degree scattering time for diffusion parallel to the background magnetic field is reduced to between 5 and 30 cyclotron periods. Simulation results suggest that Type 1 supernova remnants may be the principal sites of cosmic ray acceleration.

Max, C. E.↗
DOE OSTI2016

Spatial-dependent propagation of cosmic rays results in spectrum of proton, ratios of p-bar /p, B/C AND anisotropy of nuclei

Recent precise measurements of cosmic ray spectra revealed an anomalous hardening at ∼200 GV, observed by the ATIC, CREAM, PAMELA, and AMS02 experiments. Particularly, the latest observation of the p-bar /p ratio by AMS02 demonstrated a flat distribution, which further validated the spectral anomalies of secondary particles. All those new phenomena indicated that the conventional propagation model of cosmic rays meets a challenge. In this work, the spatial-dependent diffusion coefficient D(r,z,p) is employed by tracing the source distribution under the physical picture of the two-halo model in the DRAGON package. Under such a scenario, the model calculation will result in two-component spectra for primary nuclei. Due to the smaller rigidity dependence of D(r,z,p) in the galactic disk, the ratios secondary-to-primary will inevitably be flatter and the expected anisotropy of cosmic rays will be much more attenuated than in the conventional model. As a result, we can reproduce the spectral hardening of protons, the flat ratios of p-bar /p and B/C, and consistent anisotropy from ∼100 GeV to ∼100 TeV by only adopting one set of spatial-dependent diffusion coefficients D(r,z,p) in a galactic disk.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1967

Cosmic-ray bursts

Frequency distributions and energy spectra of cosmic ray showers

FREQUENCY DISTRIBUTION↗
NASA NTRS1982

Gradients of galactic cosmic rays and anomalous helium to more than 23 A.U. during the increase of solar modulation in 1978-80

During the transition to solar maximum (1978-81) the radial gradient of high energy galactic cosmic rays increased slightly, while the gradients of lower energy cosmic rays and the anomalous helium decreased. It is concluded that (1) Pioneer-10 at about 23 AU was still deep in a modulation region extending to more than 50 AU for both the galactic cosmic rays and the anomalous helium component, and (2) the modulation is controlled by changes in the size/geometry of heliospheric magnetic fields and/or propagation parameters, changes associated with large solar-flare shocks in 1978 and later.

Bastian, T. S.↗
NASA NTRS2012

Preliminary Design of a Galactic Cosmic Ray Shielding Materials Testbed for the International Space Station

The preliminary design of a testbed to evaluate the effectiveness of galactic cosmic ray (GCR) shielding materials, the MISSE Radiation Shielding Testbed (MRSMAT) is presented. The intent is to mount the testbed on the Materials International Space Station Experiment-X (MISSE-X) which is to be mounted on the International Space Station (ISS) in 2016. A key feature is the ability to simultaneously test nine samples, including standards, which are 5.25 cm thick. This thickness will enable most samples to have an areal density greater than 5 g/sq cm. It features a novel and compact GCR telescope which will be able to distinguish which cosmic rays have penetrated which shielding material, and will be able to evaluate the dose transmitted through the shield. The testbed could play a pivotal role in the development and qualification of new cosmic ray shielding technologies.

Gaier, James R.↗
DOE OSTI2022

Search for Spatial Correlations of Neutrinos with Ultra-high-energy Cosmic Rays

For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data are provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above ∼50 EeV are provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino sample optimized for point-source searches to search for excesses of neutrino clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses have found a significant excess, and previously reported overfluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs.

79 ASTRONOMY AND ASTROPHYSICS↗