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  • ASTROPHYSICS  (74)
  • GENERAL
  • SPACE RADIATION
  • 1975-1979  (98)
  • 1960-1964
  • 1955-1959
  • 1978  (98)
  • 1
    Publication Date: 2011-08-17
    Description: The paper reports measurement of the antiproton-to-proton and antihelium-to-helium ratios in the 4-100 GeV/c range. A superconducting magnet spectrophotometer obtained the data during a balloon flight in May 1976. The upper limit value for the antiproton ratio is 0.0005 in the 4.2-12.5 GeV/c range. This value is only slightly higher than the expected value for a leaky box-model and nearly equal to the value expected in the Peter-Westergard model. It is suggested that this upper limit value rules out the closed galaxy model. Upper limit values for the antihelium ratio are 0.000058 in the 4-10 GeV/c range; less than 0.0001 in the 4-33 GeV/c range; and less than 0.01 in the 33-100 GeV/c range. The interpretation of the raw data is explained.
    Keywords: SPACE RADIATION
    Type: Nature; 274; July 13
    Format: text
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  • 2
    Publication Date: 2011-08-17
    Description: Three aircraft flights at 12.5 km have yielded data on cosmic-ray neutron-flux densities, neutron dose equivalent rates, and exposure rates for ionizing radiation. The data, collected at 45, 38, and 48 degrees N, indicate: (1) neutron dose equivalent rates of 0.20, 0.14, and 0.22 mrem/hour, (2) exposure rates from the ionizing component of 0.37, 0.31, and 0.41 mR/hour, (3) that the dose equivalent from 3-13-MeV neutrons is 30% of the total for all neutrons, (4) that exposure rates decrease exponentially with decreasing pressure altitude with a 140 g/sq cm attenuation length at 43 degrees N geomagnetic latitude, and (5) that the ionizing component of cosmic ray secondaries is less sensitive to latitude changes than the neutron component.
    Keywords: SPACE RADIATION
    Type: Health Physics; 34; Apr. 197
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  • 3
    Publication Date: 2019-06-27
    Description: A propagation model which combines a Gaussian profile for particle release from the sun, with interplanetary particle densities predicted by focused diffusion, was proposed to explain the propagation history of flare associated energetic particles. This model, which depends on only two parameters, successfully describes the time-intensity profiles of 30 proton and electron events originating from the western hemisphere of the sun. Generally, particles are released from the sun over a finite interval. In almost all events, particle release begins at the time of flare acceleration.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-79534
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-27
    Description: Progress of the study of cosmic ray neutrons is described. Data obtained aboard flights from Hawaii at altitudes of 41,000 and 45,000 feet, and in the range of geomagnetic latitude 17 N less than or equal to lambda less than or equal to 21 N are reported. Preliminary estimates of neutron spectra are made.
    Keywords: SPACE RADIATION
    Type: NASA-TM-79881 , LBL-6738
    Format: application/pdf
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  • 5
    Publication Date: 2019-06-27
    Description: Observations of three strong interstellar UV absorption lines of N I (1199 A), N II (1083 A), and Si III (1206 A) in 47 stars of widely varying distance and a variety of spectral types are analyzed to obtain a velocity distribution function for the interstellar gas. A technique based on the maximum and minimum velocities observed along a line of sight is adopted because of heavy line blending, and results are discussed for both power-law and exponential distribution functions. The expected distribution of radiative-phase supernova remnants (SNRs) in the interstellar medium is calculated as a function of SNR birthrate and of the interstellar density in which they evolve. The results are combined with observed distance estimates, and it is shown that an interstellar density in excess of 0.1 per cu cm would be required to keep the SNRs sufficiently confined so that their cross sections are consistent with the observed number of components. The alternative possibility is considered that SNRs do not enter the radiative phase before escaping from the Galaxy or colliding with neighboring remnants.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 223
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  • 6
    Publication Date: 2019-06-27
    Description: Scans of interstellar ultraviolet absorption lines of N I, N II, and Si III for 17 stars are combined with previously published data for 30 stars. The extremal velocities at which detectable absorption occurs are tabulated, and it is shown that these are correlated for the three species. The data suggest that intermediate-velocity gas (20 to 60 km/s), best known from Na I and Ca II absorption, contains both neutral and ionized hydrogen. Features characteristic of intermediate-velocity isothermal shocks (greater than 60 km/s) are conspicuously rare. The intermediate-velocity gas may be in the form of clouds containing both H I and H II regions or of radiative shocks propagating in the interstellar medium; in the latter case the gas should be detectable in H-alpha emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 220
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  • 7
    Publication Date: 2019-07-13
    Description: An airborne superconducting magnet spectrometer was used to obtain measurements on 700,000 protons and 50,000 helium nuclei of rigidity greater than about 4 GV. The rigidity spectra of protons and helium nuclei in the 9-100 GV range are determined. In the cited range, the proton and helium nuclei can be represented by a power law in rigidity, with an index of 2.78 + or - 0.03 and 2.80 + or - 0.03 respectively. An upper limit on H-2/p of 10% at 35 GeV/nucleon is established
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Aug 13, 1977 - Aug 26, 1977; Plovdiv; Bulgaria
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  • 8
    Publication Date: 2019-06-27
    Description: A balloon-borne magnetic core digitized spark chamber with two assemblies of spark-chambers above and below the scintillation counters was used to measure the medium energy gamma ray flux from the galactic center region. Gamma ray calculations are based on the multiple scattering of the pair electrons in 15 aluminum plates interleaved in the spark chamber modules. Counting rates determined during ascent and at ceiling indicate the presence of diffuse component in this energy range. Preliminary results give an integral flux between 15 and 70 MeV compared to the differential points in other results.
    Keywords: SPACE RADIATION
    Type: NASA-TM-78331 , INPE-1218-PE/122
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  • 9
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    Publication Date: 2019-06-27
    Description: Recent abundance determinations in intermediate-velocity clouds near the Orion association have shown that silicon abundances may be nearly cosmic even in clouds with a velocity as low as 40 to 50 km/sec. It is argued that grain destruction in radiative shocks traveling perpendicular to the magnetic field may be much more effective than was previously considered. The destruction mechanism consists of acceleration of the gyromotion of the grains about their drift center owing to magnetic field compression, followed by sputtering of the high-velocity grains by He and (CNO) atoms. It is found that MgSiO3 grains may be almost fully destroyed in shocks of velocity greater than 80 km/sec and graphite grains substantially destroyed at shock velocities of 100 km/sec.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 10
    Publication Date: 2019-06-27
    Description: Analytical arguments and a numerical hydrodynamic code are used to investigate spherically symmetric accretion onto a compact object, in an attempt to provide some insight into gas flows heated by an outgoing X-ray flux. It is shown that preheating of spherically symmetric accretion flows by energetic radiation from an X-ray source results in time-dependent behavior for a much wider range of source parameters than was determined previously and that there are two distinct types of instability. The results are compared with observations of X-ray bursters and transients as well as with theories on quasars and active galactic nuclei that involve quasi-spherically symmetric accretion onto massive black holes. Models based on spherically symmetric accretion are found to be inconsistent with observations of bursters and transients.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 226
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