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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 343 records · Page 19
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NASA NTRS1993

HILT - A heavy ion large area proportional counter telescope for solar and anomalous cosmic rays

The HILT sensor has been designed to measure heavy ion elemental abundances, energy spectra, and direction of incidence in the mass range from He to Fe and in the energy range 4 to 250 MeV/nucleon. With its large geometric factor of 60 sq cm sr the sensor is optimized to provide compositional and spectral measurements for low intensity cosmic rays (i.e. for small solar energetic particle events and for the anomalous component of cosmic rays). The instrument combines a large area ion drift chamber-proportional counter system with two arrays of 16 Li-drift solid state detectors and 16 CsI crystals. The multi dE/dx-E technique provides a low background mass and energy determination. The sensor also measures particle direction. Combining these measurements with the information on the spacecraft position and attitude in the low-altitude polar orbit, it will be possible to infer the ionic charge of the ions from the local cutoff of the Earth's magnetic field. The ionic charge in this energy range is of particular interest because it provides unique clues to the origin of these particles and has not been investigated systematically so far. Together with the other instruments on board SAMPEX (LEICA, MAST, and PET), a comprehensive measurement of the entire solar and anomalous particle population will be achieved.

Klecker, Berndt↗
NASA NTRS1975

Recent perspectives in solar physics - Elemental composition, coronal structure and magnetic fields, solar activity

Elemental abundances in the solar corona are studied. Abundances in the corona, solar wind and solar cosmic rays are compared to those in the photosphere. The variation in silicon and iron abundance in the solar wind as compared to helium is studied. The coronal small and large scale structure is investigated, emphasizing magnetic field activity and examining cosmic ray generation mechanisms. The corona is observed in the X-ray and EUV regions. The nature of coronal transients is discussed with emphasis on solar-wind modulation of galactic cosmic rays. A schematic plan view of the interplanetary magnetic field during sunspot minimum is given showing the presence of magnetic bubbles and their concentration in the region around 4-5 AU by a fast solar wind stream.

Newkirk, G., Jr.↗
NASA NTRS2009

Charged Particle Environments in Earth's Magnetosphere and their Effects on Space System

This slide presentation reviews information on space radiation environments important to magnetospheric missions including trapped radiation, solar particle events, cosmic rays, and solar winds. It also includes information about ion penetration of the magnetosphere, galactic cosmic rays, solar particle environments, CRRES internal discharge monitor, surface charging and radiation effects.

Minow, Joseph I.↗
NASA NTRS1985

Ground increase of cosmic ray intensity on February 16, 1984

The event of February 16, 1984 is one of the two largest ground increases of solar cosmic rays (CR) in the last two cycles of solar activity. This event happended at a decrease of the 21-st cycle against a quiet background. Although at the beginning of 1984 the observed indices of solar activity were higher than those at the end of 1983, the day of February 16 16 may be characterized as very quiet. On that day the geomagnetic perturbance (Sigma F sub p = 14, A sub p = 7) was the lowest in February. After a small Forbush decrease due to the magnetic storm of February 12-13, the CR intensity almost completely recovered by February 16. Thus, the solar particles that came to the Earth on February 16 got into a practically unperturbed magnetosphere, and the variations of secondary CR induced by these particles were not superimposed on any other substantial variations of extraterrestrial or magnetospheric origin.

Belov, A. V.↗
NASA NTRS1980

Solar modulation of galactic cosmic rays

The current theory for the solar modulation of galactic cosmic rays is reviewed briefly. The four basic mechanisms which are important for modulation-diffusion, effects associated with the large-scale magnetic field, convection, and energy change - are discussed in simple terms. The equation which describes cosmic-ray behavior in the heliosphere is presented and some sample solutions are considered. It is pointed out that, although the basic mechanisms which describe the cosmic-ray behavior are understood, the actual cause of the variation in the cosmic-ray flux over the solar cycle, or over longer intervals, is beyond current comprehension.

Fisk, L. A.↗
NASA NTRS1993

Cosmic ray diurnal anisotropy for a solar magnetic cycle

Cosmic ray diurnal anisotropy at high primary rigidities is extended for the 1980-1987 period. The computed values of the limiting primary rigidity for the period vary over the range 30 GV to 200 GV. For the previously studied 1965-1980 period, the mean value of the amplitude of the anisotropy is 0.5 percent. The amplitude of the diurnal anisotropy for 1965 and 1986-1987 is about 20 percent smaller. Very large amplitudes of diurnal variation are observed during the 1982-1985 period, at all primary rigidities. The value of the coupled variable lambda(parallel) x G(r) found to remain constant at about 1 percent for qA less than zero solar magnetic polarity epochs, independent of the primary rigidity. Its value is significantly lower for qA greater than zero epochs.

Ahluwalia, H. S.↗
NASA NTRS2004

Exposure and Terrestrial Histories of New Lunar and Martian Meteorites

Cosmogenic nuclide studies of lunar and Martian meteorites have contributed significantly to our understanding of these objects. By measuring a combination of cosmogenic stable- and radionuclides, we can determine a number of important properties of those meteorites. Most lunar meteorites have complex cosmic ray exposure histories, having been exposed both at some depth on the lunar surface (2 irradiation) before their ejection and as small bodies in space (4 irradiation) during transport from the Moon to the Earth. On the other hand, we have not observed evidence of complex exposure history for any Martian meteorites, so far. These exposures were then followed by residence on Earth s surface, a time commonly referred to as the terrestrial age. In addition to their complement of galactic cosmic ray (GCR) produced nuclides some lunar and Martian meteorites contain nuclides produced by solar cosmic rays (SCR). Unraveling the complex history of these objects requires the measurement of at least four cosmogenic nuclides. The specific goals of these measurements are to constrain or set limits on the following shielding or exposure parameters: (1) the depth of the sample at the time of ejection from the Moon or Mars; (2) the transit time (4 exposure age) from ejection off the lunar or Martian surface to the time of capture by the Earth and (3) the terrestrial residence time. The sum of the transit time and residence time yield an ejection age. The ejection age, in conjunction with the sample depth on the Moon or Mars, can then be used to model impact and ejection mechanisms.

Nishiizumi, K.↗
NASA NTRS1989

Neon isotope studies of Fayetteville and Kapoeta meteorites and clues to ancient solar activity

Under the assumption that the solar-flare bombardment of the irradiated grains of gas-rich meteorites occurred about 4.5 b.y. ago on the parent body regoliths at 3 A.U., an estimate of the solar cosmic ray-produced Ne-21 is made by studying etched pyroxene minera separates from both light and dark portions of the gas-rich meteorites Fayetteville and Kapoeta. Excesses of solar cosmic ray Ne-21 were observed in dark portions of these meteorites, after accounting for their galactic cosmic ray Ne-21 production and solar flare Ne-21. In order to produce the estimated solar cosmic ray Ne-21 in the present samples, highly enhanced solar cosmic ray proton fluxes from the ancient sun are required.

Padia, J. T.↗
NASA NTRS1980

Solar flare and galactic cosmic ray tracks in lunar samples and meteorites - What they tell us about the ancient sun

Evidence regarding the past activity of the sun in the form of nuclear particle tracks in lunar samples and meteorites produced by heavy ions in galactic cosmic rays and solar flares is reviewed. Observations of track-rich grains found in deep lunar cores and meteorite interiors are discussed which demonstrate the presence of solar flare activity for at least the past 4 billion years, and the similarity of track density profiles from various lunar and meteoritic samples with those in a glass filter from Surveyor 3 exposed at the lunar surface for almost three years is presented as evidence of the relative constancy of the solar flare energy spectrum over the same period. Indications of a heavy ion enrichment in solar flares are considered which are confirmed by recent satellite measurements, although difficult to quantify in lunar soil grains. Finally, it is argued that, despite previous claims, there exists as yet no conclusive evidence for either a higher solar activity during the early history of the moon or a change in galactic cosmic ray intensity, average composition or spectrum over the last 50 million years.

Crozaz, G.↗
NASA NTRS1983

The association of energetic particles and shocks in the heliosphere

The observational and theoretical work on heliospheric shocks and cosmic rays in the recent past is surveyed. The data have come mainly from spacecraft in the regions from 0.3-25 AU, and include detection of particles and plasma waves upstream of the earth's bow shock. The theory of shock acceleration is reviewed, together with analytical models of energetic particle enhancement in association with shocks or shocks within the heliosphere. It has been determined that shocks in the heliosphere are associated with energetic suprathermal particles, which are conversely all associated with shocks. Solar cosmic rays and other anomalous components are therefore accelerated by shocks, a factor that is significant for studies of the acceleration mechanisms for galactic cosmic rays. The Solar Polar Mission will provide data on all solar latitudes, and the ISEE-3 spacecraft will continue to gather information on shock accelerated ions in travelling interplanetary shock waves.

Lee, M. A.↗
NASA NTRS1985

The 1973-1984 Solar Modulation of Cosmic Ray Nuclei

As a continuation of the program of solar modulation studies, new measurements were carried out with the cosmic ray telescope on the Earth satellite IMP-8, of the intensity time variations and the energy spectra of galactic cosmic ray protons, helium, carbon and oxygen from 1980 through 1984 including the recent solar maximum. In order to test the applicability of a steady state model of solar modulation during a period which includes times of rapidly changing modulation, these fluxes were equated with the predictions of a conventional model of solar modulation which assumes equilibrium between modulation mechanisms. It is found that for a reasonable range of variations of the diffusion coefficient the model predictions can be made to agree with the measurements at essentially all times during the studied period. The model can account also for the observed hysteresis effects between cosmic rays of different rigidities.

Garcia-Munoz, M.↗