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  • GEOPHYSICS
  • SPACE RADIATION
  • 1995-1999  (4)
  • 1985-1989
  • 1996  (4)
  • 1
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    Light ion components of the galactic cosmic rays: Nuclear interactions and transport theory (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-04-02
    Description: Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy induced reactions. In the primary GCR, He-4 is the most abundant nucleus after H-1. However, there are also a substantial fluxes of H-2 and He-3. In this paper we describe theoretical models based on quantum multiple scattering theory for the description of light ion nuclear interactions. The energy dependence of the light ion fragmentation cross section is considered with comparisons of inclusive yields and secondary momentum distributions to experiments described. We also analyze the importance of a fast component of lights ions from proton and neutron induced target fragementation. These theoretical models have been incorporated into the cosmic ray transport code HZETRN and will be used to analyze the role of shielding materials in modulating the production and the energy spectrum of light ions.
    Keywords: SPACE RADIATION
    Type: Advances in Space Research (ISSN 0273-1177); 17; 2; p. (2)77-(2)86
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    NASA TECHNICAL REPORTS
  • 2
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    Shielding against galactic cosmic rays (1996)
    In:  Other Sources
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    Publication Date: 2019-04-02
    Description: Ions of galactic origin are modified but not attenuated by the presence of shielding materials. Indeed, the number of particles and the absorbed energy behind most shield materials increases as a function of shield thickness. The modification of the galactic cosmic ray composition upon interaction with shielding is the only effective means of providing astronaut protection. This modification is intimately conntected with the shield transport porperties and is a strong function of shield composition. The systematic behavior of the shield properites in terms of microscopic energy absorption events will be discussed. The shield effectiveness is examined with respect to convectional protection practice and in terms of a biological endpoint: the efficiency for reduction of the probability of transformation of shielded C3H1OT1/2 mouse cells. The relative advantage of developing new shielding technologies is discussed in terms of a shield performance as related to biological effect and the resulting uncertainty in estimating astronaut risk.
    Keywords: SPACE RADIATION
    Type: Advances in Space Research (ISSN 0273-1177); 17; 2; p. (2)31-(2)36
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    NASA TECHNICAL REPORTS
  • 3
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    Overview of nuclear fragementation models and needs (1996)
    In:  Other Sources
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    Publication Date: 2019-04-02
    Description: It has been known for some time that adequate assessment of spacecraft requirements and concomitant estimates of astronaut radiation exposures from galactic cosmic radiation requires accurate, quantitative methods for characterizing these radiation fields as they pass through thick absorbers. The main nuclear interaction processes involved are nuclear elastic an inelastic collisions, and nuclear breakup (fragmentation) and electromagnetic dissociation (EMD). Nuclear fragmenation and EMD are important because they alter the elemental and isotopic composition of the transported radiation fields. At present, there is no suitable accurate theory for predicting nuclear fragmentation cross sections for all collision pairs and energies of interest in space radiation protection. Typical cross-section differences between theory and experiment range from about 25 percent to a factor of two. The resulting errors in transported flux, for high linear energy transfer (LET) particles, are compared to these cross-sections errors. In this overview, theoretical models of heavy ion fragmentation currently used to generate input data bases for cosmic-ray transport and shielding codes are reviewed. Their shortcomings are discussed. Further actions needed to improve their accuracy and generality are presented.
    Keywords: SPACE RADIATION
    Type: Advances in Space Research (ISSN 0273-1177); 17; 2; p. (2)59-(2)68
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    NASA TECHNICAL REPORTS
  • 4
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    Geomagnetic transmission disturbances and heavy-ion fluences observed in low Earth orbit during the solar energetic particle events of October 1989 (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagneitc transmission by tracing particles through the combination to the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 deg inclination space station orbit.
    Keywords: SPACE RADIATION
    Type: Advances in Space Research (ISSN 0273-1177); 17; 2; p. (2)121-(2)125
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    NASA TECHNICAL REPORTS
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