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Results for “Galactic Cosmic Ray”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The estimation of galactic cosmic ray penetration and dose rates

This study is concerned with approximation methods that can be readily applied to estimate the absorbed dose rate from cosmic rays in rads - tissue or rems inside simple geometries of aluminum. The present work is limited to finding the dose rate at the center of spherical shells or behind plane slabs. The dose rate is calculated at tissue-point detectors or for thin layers of tissue. This study considers cosmic-rays dose rates for both free-space and earth-orbiting missions.

Burrell, M. O.↗
NASA NTRS1972

Rare gas studies of the galactic cosmic ray irradiation history of lunar rocks.

Average irradiation depths and exposure ages of Tranquillity Base rocks are computed on the basis of eight analyses of the five noble gases in whole rock samples and lunar separates from lunar rocks, in conjunction with available literature data. Correlated variations in He-3/Ne-21 and Ar-38/Ne-21 reflect shielding differences. This correlation cannot be explained by diffusion losses, even though evidence for gas loss is obtained from mineral separate data. A qualitative shielding sequence is constructed which agrees reasonably well with the sequence based on Gd isotopic data.

Huneke, J. C.↗
NASA NTRS1973

Modulation of low-energy galactic cosmic rays over the present solar cycle

Explorer satellite observations of modulations in the cosmic ray spectrum during the entire period of the solar cycle show intensity variations in the proton and alpha modulated spectra. A positive correlation between plasma density and variation in cosmic ray intensity is found that breaks during the transition period when higher energy intensity is decreasing as the solar activity increases. It is suggested that the alpha particles lead the proton particles during transition periods and thus make the lag time shorter for high rigidity near the solar maximum and the solar minimum.

Vanhollebeke, M. A.↗
NASA NTRS1973

Radial gradients of galactic cosmic ray protons and helium nuclei

Variation of the cosmic ray intensity as a function away from the sun and its radial derivative is studied by plotting satellite cosmic ray measurements against sea level neutron monitor data. Results show that the solar modulation cavity extends well beyond 2 AU and that irregularities in the sun's magnetic field are carried outward radially by the solar wind, thus sweeping low energy cosmic rays out of the solar system and at the same time cooling cosmic rays reaching the earth.

Teegarden, B. J.↗
NASA NTRS1973

Interplanetary radial gradients of galactic cosmic ray protons and helium nuclei - Pioneer 8 and 9 measurements from 0.75 to 1.10 AU.

We report measurements of the radial interplanetary cosmic ray gradient made with cosmic ray instruments aboard the Pioneer 8 and 9 spacecraft. The time period covered in these studies is from January 1968 to June 1969. During this time, the radial separation of these two spacecraft varied from 0.75 to 1.10 AU from the sun. This study includes detailed measurements of the differential spectra and gradients of protons and helium nuclei from 2 to 1200 Mev/nucleon. The differential gradient for each species is observed to go through a broad maximum of about 50%/AU at energies corresponding to about 1 BV rigidity, decreasing at both lower and higher rigidities. The proton and helium nuclei gradients are small down to the lowest energies we measure.-

Webber, W. R.↗
NASA NTRS1973

Energy losses of galactic cosmic rays in the interplanetary medium.

Using realistic models of cosmic-ray propagation in interplanetary space we present, for electrons, protons and helium nuclei of a given energy near earth, calculations of their distribution in energy before entering the solar cavity and their mean energy loss. Interplanetary conditions appropriate for the epochs 1965 and 1969 have been used. Cosmic-ray energies in the range of 20 to 1000 MeV/nucleon have been considered.

Urch, I. H.↗