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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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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Anomaly in the quiet-time helium spectrum at 1 MeV per nucleon

The IMP-8 satellite observed (in 1974-1975) an unexpected hump in the solar helium spectrum between 0.6 and about 3 MeV per nucleon and an enhanced helium abundance of up to 70 MeV per nucleon. The energy spectrum of helium below 0.6 MeV per nucleon was consistent with the proton spectrum below 1.5 MeV, while the proton-to-alpha ratio was about 30. The origin of this anomalous low-energy, quiet-time helium is as yet undecided. The alpha particles could be of solar origin, could have been accelerated in the heliosphere or could be of galactic origin.

Gloeckler, G.↗
NASA NTRS1976

Conduction of thermal energy in the neighborhood of the earth's bow shock

The Rankine-Hugoniot equations for MHD shocks are generalized by the addition of a term to the energy conservation equation representing a nonzero heat flow in the plasma in the neighborhood of the shock. This generalization is found to be compatible with the assumption of infinite electrical conductivity. The effects of plasma waves in this treatment are of the order of the reciprocal Alfvenic Mach number squared and hence are neglected. The effect of alpha particles in the solar wind is discussed. Seven crossings of the earth's bow shock by Explorer 35 in lunar orbit are analyzed. Sufficient data are available so that the determination of a dimensionless parameter, psi, characterizing the heat-flow difference across the bow shock is possible. The values of psi indicate energy-flux densities due to heat flow which are a nonnegligible fraction of the total energy flux. Two possible interpretations of psi are discussed.

Hohlfeld, R. G.↗
NASA NTRS1976

Gamma-ray emission and nucleosynthesis of lithium by young pulsars

It is proposed that Li-7 is produced in the Galaxy primarily by alpha-alpha collisions surrounding newly born pulsars. About 10 percent of the pulsar energy losses are converted to medium-energy alpha-particles which collide in a dominantly He nebula. The problem of the origin of lithium would be solved by the scenario, and clear-cut tests by nuclear gamma-ray astronomy are described.

Clayton, D. D.↗
NASA NTRS1976

Plasma wave interactions with energetic ions near the magnetic equator

An intense band of electromagnetic noise is frequently observed near the magnetic equatorial plane at radial distance from about 2 to 9 earth radii. Recent wide band wave form measurements with the Imp 6 and Hawkeye 1 satellites have shown that the equatorial noise consists of a complex superposition of many harmonically spaced lines. Several distinctly different frequency spacings are often evident in the same spectrum. The frequency spacing typically ranges from a few hertz to a few tens of hertz. The purpose of this paper is to suggest that these waves are interacting with energetic protons, alpha particles, and other heavy ions trapped near the magnetic equator. The possible role that these waves play in controlling the distribution of the energetic ions is considered.

Gurnett, D. A.↗
NASA NTRS1976

Ground-based dosimetry support for experiment AR002

Actinomyces levoris colonies were exposed to alpha particles at the 184-inch cyclotron, and Streptomyces levoris colonies were exposed to Ne-20 ions. A description is given of the experimental conditions for each experiment along with tables listing the doses delivered to the colonies. The doses for the Actinomyces levoris exposures came from calibrations made by the cyclotron operators, while the doses for the Streptomyces levoris exposures came in part from cave calibrations and also in part from calculations.

Cassou, R.↗
NASA NTRS1976

Cosmic-ray gradients from Pioneer-10 and Pioneer-11

The paper reports Pioneer 10 and 11 observations of the variation with heliocentric distance of the intensity of cosmic-ray protons, alpha particles, and high-Z nuclei with kinetic energies of at least 480 MeV/nucleon as well as cosmic-ray electrons with energies exceeding 6 MeV. The observations were with three-channel Cerenkov counters at distances between 1.02 and 4.66 AU while the spacecraft traveled from earth to Jupiter. During the 4.5-month observation period, all the counting rates rose steadily, except when they were modified by solar events, Forbush decreases, and Jovian electron events. Two methods are employed to determine the cosmic-ray integral intensity gradient for the observation period from simultaneous data obtained by the two spacecraft; effects of solar particles, Forbush decreases, and Jovian electrons are eliminated in various ways. A radial gradient of 0.15 + or - 2.3% per AU is determined, which is considered to be consistent with zero. Theoretical gradients are computed, and the observed values are found to be an order of magnitude below the expected values. Several reasons for the discrepancy are suggested.

Axford, W. I.↗
NASA NTRS1977

Nonlinear Alfven waves in high-speed solar wind streams

A nonlinear proton distribution function that is an exact stationary solution of the nonlinear Vlasov equation and Maxwell's equations and which supports a single nonlinear transverse Alfven (ion cyclotron) wave that is circularly polarized and nondispersive is proposed for most of the observations during high-speed solar wind streams. This nonlinear distribution removes the strong Alfven wave instability, inconsistent with the persistence of the observed proton distribution functions in high-speed streams, found by the linear stability analysis. Model temperature anisotropies and drift velocities of the two spatially inhomogeneous bi-Maxwellian components are consistent with typical proton velocity distributions measured in high-speed streams at 1 AU. Two derived relations for each of the wave number and the phase velocity of the wave are obeyed within experimental uncertainties by two typical proton measurements. Our model also predicts that the alpha particle bulk flow velocity exceeds the proton particle bulk flow velocity, as is observed.

Abraham-Shrauner, B.↗
NASA NTRS1976

The surface chemical composition of lunar samples and its significance for optical properties

The surface Fe, Ti, Ca, and Si concentrations in a variety of soil and rock samples from all the Apollo sites are determined using an Auger spectrometer plus a single-pass cylindrical-mirror analyzer with a standard 15-stage BeCu electron multiplier. It is found that there are no great differences between the surface and bulk concentrations of any of the four elements in the rock samples, but the surface Fe and Ti concentrations in soil samples are higher than the bulk concentrations. Results are also reported for solar-wind simulation experiments in which a pulverized rock sample was bombarded with 2-keV alpha-particles corresponding to about a 30,000-yr dose of the solar-wind proton component. These results indicate that the chemical change induced on the surface of a rock powder by positive-ion bombardment is similar to the change from bulk to surface chemical composition in lunar soil samples. A clear correlation is observed between the surface Fe concentration and albedo of the soil samples.

Gold, T.↗
NASA NTRS1977

Narrow lines from alpha-alpha reactions

Intensities and spectral shapes of the prompt gamma-ray lines of Li-7 at 0.431 MeV and Be-7 at 0.478 MeV and of the delayed 0.478-MeV line, all resulting from alpha-alpha reactions, are calculated using recent direct measurements of the cross sections for the alpha-alpha reactions. It is found that the intensities of these lines are comparable to that of the 4.44-MeV line of C-12, so that the investigated lines should be observable in large solar flares, provided their Doppler widths are not excessively large. An evaluation of the shapes of the prompt lines indicates that for an isotropic distribution of energetic alpha-particles, the two lines merge into a broad feature which essentially cannot be distinguished from the continuum. A situation in which the delayed 0.478-MeV line could be very narrow is considered.

Kozlovsky, B.↗
NASA NTRS1977

Acceleration of protons at 32 Jovian radii in the outer magnetosphere of jupiter

During the inbound pass of Pioneer 10, a rapid ten-fold increase of the 0.2 to MeV proton flux was observed at 32 Jovian radii (R sub J). The total event lasted for 30 minutes and was made up of a number of superimposed individual events. At the time, the spacecraft was in the outer magnetosphere about 7 R sub J below the magnetic equator. Before and after the event, the proton flux was characteristic of the low flux level normally encountered between crossings of the magnetic equator. Flux changes at different energies were coherent within 1 minute; a time comparable to the time resolution of the data. The angular distributions were highly anisotropic with protons streaming towards Jupiter. A field-aligned dumbbell distribution was observed initially, and a pancake distribution just before the flux decayed to its pre-event value. The alpha particle flux changed as rapidly as the proton flux but peaked at different times. The energetic electron flux behaved differently; it increased gradually throughout the period.

Schardt, A. W.↗
NASA NTRS1978

Gamma ray facilities at the University of Maryland cyclotron

A special beam line was set up in a separate shielded experimental room to provide a low background station for gamma-ray measurements at the University of Maryland cyclotron. The transmitted beam leaving the target is gathered in by a magnetic quadrupole lens located 1.8 m further downstream and focused on a Faraday cup located on the far side of the 2.5 m thick concrete shielding wall of the experimental room. A software computer program permits timing information ot be obtained using the cyclotron beam fine structure as a time reference for the observed gamma-ray events. Measurements indicate a beam fine structure width of less than 1.2 nanoseconds repeated, for example, in the case of 140 MeV alpha particles every 90 nanoseconds. Twelve contiguous time channels of adjustable width may be set as desired with reference to the RF signal. This allows the creation of 12 separate 8192 channel analyzers.

Hornyak, W. F.↗
NASA NTRS1977

A survey on initial results of the Helios plasma experiment

The reported results are mainly based on data obtained during the first part of the Helios-1 mission. The sun was very quiet during the considered period. The data are, therefore, representative for comparatively stationary conditions in the solar corona. Data obtained concerning the protons were evaluated by means of a special computer routine. The significance of the data is discussed, taking into account the status of the corona and the interplanetary plasma during the considered part of the Helios-1 mission, fast stream structures in the region between 0.3 and 1 AU, radial gradients of fast and slow solar wind, and the separation of proton double streams and alpha-particles. Attention is also given to the 'strahl' in the electron distribution, differences between fast streams and slow plasma on the basis of the observed electron distributions, and radial gradients in the case of solar wind electron parameters.

Rosenbauer, H.↗
NASA NTRS1977

The use of Landsat for monitoring water parameters in the coastal zone

Landsats 1 and 2 have been successful in detecting and quantifying suspended sediment and several other important parameters in the coastal zone, including chlorophyll, particles, alpha (light transmission), tidal conditions, acid and sewage dumps, and in some instances oil spills. When chlorophyll a is present in detectable quantities, however, it is shown to interfere with the measurement of sediment. The Landsat banding problem impairs the instrument resolution and places a requirement on the sampling program to collect surface data from a sufficiently large area. A sampling method which satisfies this condition is demonstrated.

Bowker, D. E.↗
NASA NTRS1977

Spacecraft-produced neutron fluxes on Skylab

Estimates of neutron fluxes in different energy ranges are reported for the Skylab spacecraft. Detectors composed of uranium, thorium, and bismuth foils with mica as a fission track recorder, as well as boron foils with cellulose acetate as an alpha-particle recorder, were deployed at different positions in the Orbital Workshop. It was found that the Skylab neutron flux was dominated by high energy (greater than 1 MeV) contributions and that there was no significant time variation in the fluxes. Firm upper limits of 7-15 neutrons/sq cm-sec, depending on the detector location in the spacecraft, were established for fluxes above 1 MeV. Below 1 MeV, the neutron fluxes were about an order of magnitude lower. The neutrons are interpreted as originating from the interactions of leakage protons from the radiation belt with the spacecraft.

Quist, T. C.↗
NASA NTRS1978

Definition and detailed characterization of lunar surface units using remote observations

Remote sensing techniques are reviewed in terms of their application to the study of the lunar surface. These techniques include: reflectance spectroscopy (UV and IR), X-ray and gamma-ray analysis, alpha-particle spectroscopy, thermal emission, polarimetry, photography, and visual observation. Each technique is indexed with respect to its usefulness in either describing the appearance and location of a feature, classifying the feature in terms of a broader category, or supplying additional quantitative data. Special attention is given to the mare deposits of the Imbrium basin.

Head, J. W.↗
NASA NTRS1978

Acceleration of protons at 32 Jovian radii in the outer magnetosphere of Jupiter

A rapid ten-fold increase of proton flux was observed at 32 Jovian radii in Jupiter's outer magnetosphere. The total event lasted about 30 minutes and was composed of many individual events. Both before and after the event, proton flux was similar to the low-flux level found between crossings of the magnetic equator. Measurements of angular distributions and the time histories of proton and alpha particle channels at different energies indicate that the flux increase is caused by local acceleration. It is suggested that the average particle population in the outer magnetosphere is caused by a state of dynamic equilibrium between acceleration and loss processes.

Schardt, A. W.↗
NASA NTRS1978

Solar wind stream interfaces

Results are presented for a superposed epoch analysis of discontinuous solar wind interfaces. The average time-space profiles of stream interfaces are discussed with reference to fluid properties (flow speed, pressure ridge, density, electron and proton temperatures) and kinetic properties (electron core and halo, flow speed fluctuations, electron heat flux, alpha particles). Other aspects of stream interfaces are described, such as the persistence of individual interfaces, shock associations, the sector boundaries of the interplanetary magnetic field, and sudden impulses in the geomagnetic field. Interface position is considered in terms of the observed temperature jump. A conceptual model of high-speed stream evolution is proposed.

Gosling, J. T.↗
NASA NTRS1978

Quiet time interplanetary cosmic ray anisotropies observed from Pioneer 10 and 11

Cerenkov counters on the Pioneer 10 and 11 spacecraft, capable of detecting alpha particles and protons with energies up to 480 MeV, and nucleons and electrons with energies up to 6 MeV, have yielded data on cosmic ray anisotropies during periods of low solar activity. Observations from Pioneer 11 place east-west anisotropy at 0.41 plus or minus 0.11%, and the north-south anisotropy at near zero; Pioneer 10 results show east-west anisotropy to be approximately 0.59 plus or minus 0.18%, and the north-south component at 0.25 plus or minus 0.08%. It is noted that the Pioneer 10 observations were obtained at the 6 AU range, while those from Pioneer 11 originated closer to the sun (1.1 to 2.7 AU). Attention is given to the ratio of the perpendicular to parallel components of the diffusion coefficient, and to the large north-south anisotropy reported by Pioneer 10, an effect due possibly to gradient drift, and to an additional streaming independent of the magnetic field polarity.

Ip, W.-H.↗