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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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Analysis of data on solar cosmic ray events, collected from high-altitude balloon flights and injun i satellite observations
Interplanetary magnetic field variation properties and effects on solar cosmic rays determined through Mariner II recordings employed to develop model
Time variation of solar cosmic rays measured by high altitude balloon flights during september 3, 1960 solar flare event
The use of cosmogenic radionuclides in lunar materials as indicators of solar cosmic ray fluxes and thus solar activity over the past 10 million years is discussed. The nature of solar and galactic cosmic ray particles and their interactions with matter are reviewed, with particular emphasis on nuclide production by cosmic-ray-induced nuclear reactions. Evidence of galactic cosmic ray flux variations from measurements of radionuclide activities in meteorites is considered which has indicated changes of less than about 25-50% over the last few million years. Measurements of radionuclide activities in lunar materials which are used to determine solar cosmic ray fluxes are then examined together with direct proton measurements indicating variations in solar fluxes with different solar cycles. It is noted that whereas average solar proton fluxes determined for the last 1-10 million years from Al-26 and Mn-53 data show little variation and are similar to recent values, lunar C-14 and Kr-81 activities indicate average solar proton fluxes several times greater over the past 10,000 to 100,000 years.
A general, numerical method for calculating activities of solar cosmic ray produced radionuclides at any point within an irregularly shaped lunar rock of known surface contour and lunar surface orientation is described. This method is then used to predict the activities of Mn-53 andAl-26 as a function of postion within lunar rock 68815 for various assumed values of solar cosmic ray flux (J), rigidity (R sub 0), and rock erosion rate (ER). The predicted activities agree with the measured activities of Kohl et al. (1978) when values of R sub 0 = 100 MV, J = 70 p/sq cm-sec (4 pi, E greater than 10 MeV), ER not greater than 1 mm/m.y. and a total exposure time of 2 m.y. are assumed. These values are in agreement with those found for rocks exposed for not less than 10 m.y. and provide no evidence for variation of the average solar cosmic ray parameters between the last 2 and 10 m.y. intervals. When interpreted with the improved model the activity vs. depth profiles for three faces of 68815 show no evidence of SCR anisotropy or differential erosion.
Nuclear composition and energy spectrum of multiply charged nuclei of solar cosmic rays
Space science - satellite observation of galactic solar cosmic rays - explorer 7
The isotopic composition of hydrogen and helium in solar cosmic rays provides a means of studying solar flare particle acceleration mechanisms since the enhanced relative abundance of rare isotopes, such as H-2, H-3, and He-3, is due to their production by inelastic nuclear collisions in the solar atmosphere during the flare. Electron isotope spectrometer on an IMP spacecraft was used to measure this isotopic composition. The response of the dE/dx-E particle telescope is discussed, and alpha particle channeling in thin detectors is identified as an important background source affecting measurement of low values of (He-3/He-4). The flare-averaged results obtained for the period October, 1972 November, 1973 are given.
Low energy solar cosmic ray experiment for OGO-F using double diffused depleted silicon diodes
Anisotropic solar cosmic rays in inhomogeneous medium, investigating shell effect on propagation by one dimensional model
An approach to measuring charged spectra of solar cosmic rays is considered. These observations were made by a telescope on the IMP 6 satellite. The charge range was extended beyond charge 2 up to charge 26, and the energy range was extended to lower energies. The experiment preferentially selects rare events above charge 2 and gives them top priority for telemetry readout, thus breaking the monopoly that protons and helium nuclei otherwise would have on the telemetry. This effectively increases the number of nuclei observed above charge 2 by a factor of several hundred.
Solar cosmic ray diffusion and interplanetary magnetic field power spectrum
Interplanetary diffusion model for time dependency of intensity of solar cosmic ray event
Arrival of low-rigidity solar cosmic rays into the geomagnetic field in terms of ring current effects and limitation of the radial extent of the magnetosphere
Consideration is given to whether the modulation of low energy solar cosmic ray nuclei between the sun and earth can be so extreme that the fluxes observed at 1 AU imply (1) that the cosmic ray energy density in the solar atmosphere is comparable to the thermal energy density, and/or (2) that the cosmic ray intensity is sufficient in the solar atmosphere to produce detectable fluxes of secondary particles such as low energy positrons. It was found that such large modulation is compatible with observations, provided that the modulation occurrence is confined within a solar envelope lying within approximately 0.2 to 0.3 AU of the sun. There is, however, no compelling observational evidence to require that the modulation is this large.
Balloon-borne nuclear emulsion detection of solar cosmic ray heavy nuclei during solar burst
Experimental observations of the elemental and isotopic composition of solar flare particles are discussed. Sources and characteristics of particle-emitting solar flare events are reviewed, and techniques for separating particle species are briefly described. Data are presented for the elemental composition of the solar atmosphere, and the possibility of determining the solar helium abundance from solar cosmic-ray observations is explored. The main experimental determinations of heavy element abundances at energies greater and less than 10 MeV/nucleon are summarized, and techniques for measuring the ionic charge composition of solar cosmic rays are outlined. Models explaining heavy element enhancements are described along with processes leading to gamma-ray emission during solar flare events. Observations of the rare isotopes of hydrogen and helium during solar flare events are noted, and a lower atmospheric limit is derived for nuclear reactions leading to positron decay. The possibility of investigating low-energy solar cosmic rays by measuring the relative abundances of different elements is evaluated.
Use of constancy of helium to medium nuclei ratio in solar cosmic rays to estimate solar helium abundance