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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Intensities of high-energy cosmic rays at Mount Kanbala

General features of family events with Summary E sub gamma 200 TeV, observed by the emulsion chambers at Mt. Kanbala, are presented in comparison with the Monte Carlo simulation. The lateral and cluster structure, and the energy spectra of constituent gamma-rays and hadrons are shown to be consistent with the Monte Carlo results calculated under the assumption of heavy-enriched primary, scaling, QCD jets and increasing cross-section.

Ren, J. R.↗
NASA NTRS1985

Analytical calculation of muon intensities under deep sea-water

The study of the energy loss of high energy muons through different materials, such as rock and sea-water can cast light on characteristics of lepton interactions. There are less ambiguities for the values of atomic number (Z) and mass number (A) in sea-water than in rock. Muon intensities should be measured as fundamental data and as background data for searching the fluxes of neutrino. The average range energy relation in sea-water is derived. The correction factors due to the range fluctuation is also computed. By applying these results, the intensities deep under sea are converted from a given muon energy spectra at sea-level. The spectra of conventional muons from eta, K decays have sec theta enhancement. The spectrum of prompt muons from charmed particles is almost isotropic. The effect of prompt muons is examined.

Inazawa, H.↗
NASA NTRS1984

Nonthermal synchrotron radiation in a strong magnetic field

A synchrotron source model is presented for the origin of gamma-ray bursts from neutron stars. The field strength and length of time needed for electrons to lose sufficient energy in emitting the gamma rays are calculated, together with the efficiency of the process, limiting frequencies, and the energy output. A Monte Carlo simulation of the synchrotron radiation spectrum of an electron undergoing a self-consistent energy loss demonstrates that a process involving thermalized electrons can be sufficiently efficient to produce 30 keV gamma rays. Problems expected in using the current capabilities of detectors to scan for the projected energy spectra from fields of at least 3 x 10 to the 12th Gauss are discussed.

Bussard, R. W.↗
NASA NTRS1984

Characteristics of plasmoidlike structures in the distant magnetotail

A statistical analysis is presented of energetic particle burst events in the distant geomagnetic tail which have the particle characteristics of plasmoids as described by Hanes et al. (1984) and Scholer et al. (1984). The average velocities of the plasmoids are more or less evenly distributed between about 300 km/s and about 1000 km/s, with a mean value of about 600 km/s. Most plasmoids have a length between about 50 and 100 earth radii, with a mean value of about 80 earth radii. The proton energy spectra are always steeper than power law. The proton differential intensity at 30 keV varies between 100 and 1000 protons/sq cm/s/sr/keV, with an average value of about 500 protons/sq cm/s/sr/keV. This value is about one order of magnitude smaller than typical values in the near-earth plasma sheet.

Scholer, M.↗
NASA NTRS1984

1979 January 13 - An intense gamma-ray burst with a possible associated optical transient

The time history, energy spectra, and precise localization of the intense January 13, 1979 gamma-ray burst, observed by five spacecraft in the interplanetary network, are presented. The time history displays a pulse-afterpulse structure suggestive of periodicity. Fine time resolution spectral analysis shows that a wide variety of models can be used to fit individual spectra, while spectra integrated over longer periods are well fitted by a thermal synchrotron law, making it difficult to identify any specific emission mechanism. The precise localization may be consistent with an archival optical transient having no quiescent counterpart down to 22d mag on recent plates.

Barat, C.↗
NASA NTRS1984

The solar flare heavy ion environment for single-event upsets - A summary of observations over the last solar cycle, 1973-1983

A summary of observations of the flux of 25 to 400 MeV/nucleon heavy ions from solar flares is presented covering the period from late 1973 to early 1984. Distributions of flare occurrence frequency versus fluence, energy spectra, and composition are presented for the 30 events observed during this period, to quantify the variability of the heavy ion environment. A comparison of these data to a model environment suggests some refinements to the model. LET spectra based on the worst case flare observed are presented to illustrate the significance of the flare ion distribution and the importance of accurate shielding estimates.

Chenette, D. L.↗
NASA NTRS1985

Voyager observations of ion phase space densities in the Jovian magnetosphere

Data from the Voyager low-energy charged particle experiment (LECP) were used to calculate ion phase space densities in Jupiter's magnetosphere. The calculation of F at constant mu and J(2) requires the determination of particle fluxes at specific pitch angles and energies. It is shown that the greatest uncertainties in the determination of F from LECP data arise from the fits to the measured pitch angle distributions and differential energy spectra. An estimate is provided of this uncertainty and of others arising from model radial diffusion coefficients and magnetic fields. The general nature of the curves is consistent with inward diffusion of these energetic ions from the outer magnetosphere combined with losses near but starting beyond the orbit of Io. These losses are not consistent with simple satellite sweeping by Io alone and are probably due to an Io-torus wave-particle interaction. The lifetime against loss deduced from the data is approximately 20,000 s near Io and is a value consistent with strong diffusion losses. The measured ion loss rate declines much more rapidly than the strong diffusion loss rate as L increases from 7 to 9, suggesting that the loss rate is well below the strong-diffusion rate beyond 7 Jupiter radii for ions observed by the LECP.

Paonessa, M.↗
NASA NTRS1983

Solar flare neutrons and gamma ray lines

Energy spectrum of accelerated protons and nuclei at the site of the June 21, 1980, limb flare is derived by a new technique, using observations of the time-dependent flux of high-energy neutrons at the earth. This energy spectrum is very similar to the energy spectra of seven disk flares for which the accelerated particle spectra have been previously derived (Lingenfelter et al., 1965; Lingenfelter and Ramaty, 1967) using observations of 4-7-MeV to 2.223-MeV fluence ratios.

Lingenfelter, R. E.↗
NASA NTRS1985

Morphological study of energetic electron precipitation events using the satellite bremsstrahlung X ray technique

The precipitation of energetic electrons into the atmosphere is investigated with simultaneous measurements of bremsstrahlung X-rays, emitted from different local time sectors. The measurements were performed from the low-altitude, polar-orbiting satellite P78-1 with an array of X-ray spectrometers (21-139 keV). Magnetic local-time (MLT) profiles of the intensities and energy spectra were obtained for a broad span of L values. From approximately 0930 to 1400 MLT the average X-ray intensity was found to decrease with increasing magnetic local time, whereas from 2200 to 0200 MLT no clear trend with local time was observed. The data presented are noted to correspond closely with the relative electron precipitation (REP)-type events, though no evidence of a distinct group of REP was found.

Imhof, W. L.↗
NASA NTRS1985

Multiple-scale turbulence closure modeling of confined recirculating flows

A multiple-scale turbulence closure scheme is developed for the numerical predictions of confined recirculating flows. This model is based on the multiple-time-scale concepts of Hanjalic et al. (1980) and takes into account the non-equilibrium spectra energy transfer mechanism. Problems concerning new formulation of energy transfer rate equations and subsequent model coefficient redefinition and energy spectrum partition are discussed. Comparisons are made with several experiments of internal recirculating flows for the purpose of model validation. Numerical results using the present model show significant improvement of predictive capability over that obtained with the single-scale k-epsilon model and show promising potential for complex turbulent flow predictions.

Chen, C. P.↗
NASA NTRS1986

Gamma ray astronomy from satellites and balloons

A survey is given of gamma ray astronomy topics presented at the Cosmic Ray Conference. The major conclusions at the Cosmic Ray Conference in the field of gamma ray astronomy are given. (1) MeV-emission of gamma-ray bursts is a common feature. Variations in duration and energy spectra from burst to burst may explain the discrepancy between the measured log N - log S dependence and the observed isotropy of bursts. (2) The gamma-ray line at 1.809 MeV from Al(26) is the first detected line from a radioactive nucleosynthesis product. In order to understand its origin it will be necessary to measure its longitude distribution in the Milky Way. (3) The indications of a gamma-ray excess found from the direction of Loop I is consistent with the picture that the bulk of cosmic rays below 100 GeV is produced in galactic supernova remnants. (4) The interpretation of the large scale distribution of gamma rays in the Milky Way is controversial. At present an extragalactic origin of the cosmic ray nuclei in the GeV-range cannot be excluded from the gamma ray data. (5) The detection of MeV-emission from Cen A is a promising step towards the interesting field of extragalactic gamma ray astronomy.

Schoenfelder, V.↗
NASA NTRS1986

Galactic cosmic ray composition

An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

Meyer, J. P.↗
NASA NTRS1986

Observational properties of cosmic gamma-ray bursts

A brief overview of the major observational results obtained in gamma-ray burst studies is presented. Also discussed is to what extent the thermonuclear model, which appears at present to be the most plausible, can account for the observed properties of the bursts. The investigation of gamma-ray bursts should cover observations of the time histories of events, energy spectra, and their variablility, source localization, and inspection of the localization regions during the active and quiescent phases of the source in other wavelengths, as well as, evaluation of the statistical distributions of the data obtained.

Mazets, E. P.↗
NASA NTRS1986

Secondary antiproton production in relativistic plasmas

Angular and energy spectra of bremsstrahlung have been calculated from anisotropic electron distributions in solar flares. Results have been compared to observations of gamma-ray limb-brightening and the data on the variation of the gamma-ray spectrum with flare position on the sun.

Dermer, C. D.↗
NASA NTRS1986

The acceleration and propagation of solar flare energetic particles

A review of the most pertinent data on solar energetic particles is presented, and the implications of the data are discussed, taking into account radio emissions, hard X-rays, gamma rays, energy spectra and electron-proton correlations, chemical compositions, and isotopic and ionic compositions. The mechanisms of solar flare particle acceleration are considered along with solar flare particle spectra in interplanetary space. Attention is given to stochastic acceleration, shock acceleration, acceleration in direct electric fields, the mean free paths of solar electrons and protons in interplanetary space, and an illustration of the probable effect of adiabatic deceleration on the spectra of solar flare ions at the time of maximum.

Forman, M. A.↗
NASA NTRS1986

High energy irradiations simulating cosmic-ray-induced planetary gamma ray production. I - Fe target

Two thick Fe targets were bombarded by a series of 6 GeV proton irradiations for the purpose of simulating the cosmic ray bombardment of planetary objects in space. Gamma ray energy spectra were obtained with a germanium solid state detector during the bombardment, and 46 of the gamma ray lines were ascribed to the Fe targets. A comparison between observed and predicted values showed good agreement for Fe lines from neutron inelastic scattering and spallation reactions, and less satisfactory agreement for neutron capture reactions, the latter attributed to the difference in composition between the Fe target and the mean lunar abundance used in the modeling. Through an analysis of the irradiation results together with continuum data obtained in lunar orbit, it was found that 100 hours of measurement with a current instrument should generate a spectrum containing approximately 20 lines due to Fe alone, with a 2-sigma sensitivity for detection of about 0.2 percent.

Metzger, A. E.↗