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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The abundances of solar accelerated nuclei from carbon to iron.

Revised observation periods and new data are found to confirm previous evidence that the overabundance of solar-flare nuclei with respect to solar photospheric and coronal abundances increases with increasing atomic number. It is also verified that enhancements can vary from flare to flare and that this variability is large enough to explain the differences observed by various investigators regarding the magnitude of solar-flare high-Z particle enhancements. Additional evidence for a two-stage solar acceleration mechanism is obtained. It is shown that the galactic cosmic-ray source composition displays a similar overabundance as a function of atomic number.

Mogro-Campero, A.↗
NASA NTRS1973

Far-infrared observations of galactic nuclei.

M82 (NGC 3034) and NGC 253 have been detected at wavelengths from 27 to 125 microns by using a 30-cm airborne IR telescope and a multiband photometer. Spectral power distribution curves are plotted for the galactic nuclei. Tables of obtained data are also given.

Harper, D. A., Jr.↗
NASA NTRS1973

Nuclei of planetary nebulae.

Survey of available information about the spectra of emission-line nuclei of planetary nebulae. The spectral features are classified into groups corresponding to WR, O VI, Of, and WR-Of types, and the observations are interpreted in terms of astrophysical processes occurring in these objects.

Smith, L. F.↗
NASA NTRS1973

A new model for cometary nuclei.

A new model for the nucleus of comets is presented, hypothesizing formation at large heliocentric distances from many independent solid bodies. It is shown that such a configuration would collapse to a single assemblage if it is to survive into the inner solar system. Prior to collapse, the bodies would be subject to coating by interstellar gas and particles, which would form the material lost into the coma at subsequent inner solar system perihelia. Quantitative estimates place an upper limit to the body sizes of 2.3 m and a lower limit of the number as 3 x 10 to the 10th power with sizes of a few tenths of a micron and numbers of about 10 to the 33rd power most probable. The major structural and evolutionary features of such comet nuclei are consistent with the Whipple icy-conglomerate model.

O'Dell, C. R.↗
NASA NTRS1973

Unusual chemical compositions of noctilucent-cloud particle nuclei

Two sounding rocket payloads were launched from the ESRO range in Sweden during a noctilucent cloud display. Large numbers of submicron particles were collected, most of which appear to be made up of a high density material coated with a low density material. Typical electron micrographs are shown. Particle chemical compositions have been measured by use of dispersive X-ray analysis equipment attached to an electron microscope and have revealed that most of the high density particle nuclei have atomic weights greater than iron.

Hemenway, C. L.↗
NASA NTRS1974

Charge composition of high energy heavy primary cosmic ray nuclei

A detailed study of the charge composition of primary cosmic radiation for about 5000 charged nuclei from neon to iron with energies greater than 1.16 GeV/nucleon is presented. Values are obtained after corrections were made for detector dependences, atmospheric attenuation, and solar modulation. New values of 38.5, 32.4, 23.7, and 16.8 g/sq cm for the attenuation mean free paths in air for the same charge groups are presented.

Price, R. D.↗
NASA NTRS1973

The V-K colours of the nuclei of bright galaxies

Photometric observations of the nuclei of the galaxies M32, M33, M51, NGC5195 and M101 are reported. These give U-B, B-V, H-K and V-K colours for each object and the K-L colour for M32. No short-wavelength infra-red excesses are found. For M32, published population models (Spinrad & Taylor) predict a V-K colour too red to be compatible with the observations.

Penston, M. V.↗
NASA NTRS1974

On the charge state of low energy Fe nuclei accelerated by solar flares

Using sounding rockets, the differential energy spectra of Fe in three solar flares between 0.3 and 50 MeV/nuc were measured. In one of these flares, the geomagnetic field was undisturbed, and the Fe spectrum showed a peak at approximately 2 MeV/nuc. Interpreting this observation with the established quiet time geomagnetic cutoffs, it was calculated that the charge of 2 MeV/nuc Fe is 22 plus or minus 1 instead of the equilibrium value of about 16 for Fe in neutral matter. This nonequilibrium state of ionization imposes a constraint on the flare mechanism and suggests the importance of the flash-phase flare plasma for ionizing heavy nuclei prior to acceleration.

Sullivan, J. D.↗
NASA NTRS1974

Results obtained with position sensitive multiwire proportional chambers with helium, carbon, and oxygen nuclei

Spatial resolution performance results obtained at the Lawrence Radiation Laboratory Bevatron with prototype multiwire proportional chamber spatial detectors with integral delay line readout are presented. The effects due to incident nuclei charge, chamber operating parameters, chamber design, electronics, gas mixtures, and magnetic field presence have been investigated and are discussed.

Emming, J. G.↗
NASA NTRS1974

On the steady flow of gas from the nuclei of Seyfert galaxies

Heating of gas energy released during explosive events produces hot winds in Seyfert nuclei. Steady-state solutions indicate that supersonic velocities up to about 800 km per sec are obtainable. Lyman continuum radiation emitted by the wind ionizes and maintains temperature of cooler gas clouds seen in emission, and dominates energy losses during early stages of expansion. A study of stability of the thermal equilibrium state leads to a two-component model: a hot stable phase (the wind), in pressure equilibrium with a cooler stable phase (clouds). Extreme variations in cloud electron densities are a consequence of the steep decrease with radius of external pressure. Cloud dynamics are related to the radius of formation and internal parameters. Permitted lines of H are emitted by high-density clouds formed at the base of the wind, while forbidden lines arise in radially moving clouds, produced throughout the wind.

Wolfe, A. M.↗
NASA NTRS1974

Observation of transiron solar-flare nuclei in an Apollo 16 command-module window

The first measurements of the fluence of solar particles with nuclear charges not less than 32 and 44 are presented, along with the enhancement factors found. Using a track-etching technique, these transiron nuclei were detected in a window from the Apollo 16 command module which was exposed outside the magnetosphere during the solar-particle event of Apr. 18, 1972.

Shirk, E. K.↗
NASA NTRS1974

Rigidity spectrum of z greater than or equal to 3 cosmic-ray nuclei in the range 4-285 GV and a search for cosmic antimatter

A measurement, using the magnetic emulsion spectrometer system, of the differential rigidity spectrum of Z greater than or equal to 3 nuclei of the galactic cosmic radiation is presented. The system was flown on Aug. 22, 1969, from Palestine, Texas. The instrument floated above 125,000 feet for eight hours. The data in the rigidity range 8-285 GV can be represented by a power-law spectrum in rigidity, J(rho) = A rho to the minus gamma power, with the exponent gamma = 2.6 plus or minus 0.10. The spectrum in the range 15-285 GV is also described by the same exponent, gamma = 2.6 plus or minus 0.25. The data below 8 GV cannot be described by the same power law without invoking solar modulation. A set of nonunique parameters for modulation are given. Upper limit for the fraction of antimatter in the rigidity range 4-125 GV is .005 with 95% confidence limit.

Golden, R. L.↗
NASA NTRS1974

Nuclei of planetary nebulae

The nuclei of planetary nebulae are examined both observationally and theoretically. It is seen that the region occupied by these stars in the logT-logL diagram is quite wide but consistent with a general progression of stars from high to low luminosity, with a noticeable but not large increase in luminosity during the early phase. The 'evolutionary path' is intrinsically quite wide and may indicate the evolution of stars under different conditions or non-monotonic passage along the mean path. Among the several theoretical approaches to this subject, only the double shell burning models seem to offer enough luminosity and short enough timescales to match the observations.

Odell, C. R.↗
NASA NTRS1975

Composition and energy spectra of heavy nuclei of unknown origin detected on Skylab

At the orbit of Skylab, steeply falling energy spectra of nuclei with atomic numbers of at least 8 and energies between about 10 and 40 MeV/amu at intensities much higher than seen outside the magnetosphere were observed. The composition is consistent with that of the solar corona. It is suggested that heavy solar-wind ions enter the magnetosphere, are accelerated, and populate the inner radiation belt.

Chan, J. H.↗
NASA NTRS1974

Gravitational-wave bursts from the nuclei of distant galaxies and quasars: Proposal for detection using Doppler tracking of interplanetary spacecraft

Supermassive black holes which exist in the nuclei of many quasars and galaxies are examined along with the collapse which forms these holes and subsequent collisions between them which produce strong, broad-band bursts of gravitational waves. Such bursts might arrive at earth as often as 50 times per year--or as rarely as once each 300 years. The detection of such bursts with dual-frequency Doppler tracking of interplanetary spacecraft is considered.

Thorne, K. S.↗
NASA NTRS1976

The study of the physics of cometary nuclei

A semiannual progress report describing the work completed during the period 1 September 1975 to 29 February 1976 on the physics of cometary nuclei was given. The following items were discussed: (1) a paper entitled ""A speculation about comets and the earth'', (2) a chapter entitled"" The physics of comets'' for ""Reviews of Astronomy and Astrophysics'', (3) continuing work on split comets, and (4) results dealing with a new application of nongravitational solar-radial forces as a measure of comet nucleus dimensions and activity.

Whipple, F. L.↗
NASA NTRS1976

Energy spectra of cosmic ray nuclei: 4z26 and .3E2 GeV/amu

Energy spectra of cosmic ray nuclei in the charge range 5 is less than or equal to z less than or equal to 26 have been derived from the response of an acrylic plastic Cerenkov detector. Data were obtained using a balloon borne detector and cover the energy range 320 is approximately less than e approximately less than 2200 MeV. amu. Spectra are derived from a formal deconvolution using the method of Lezniak (1975). Relative spectra of different elements are compared by observing charge ratios. Secondary primary ratios are observed to decrease with increasing energy, consistent with the effect previously observed at higher energy. Primary to primary ratios are constant for 6 is less than or equal to z less than or equal to 26 and 14 is less than or equal to z less than or equal to 26 but vary for 10 is less than or equal to z less than or equal to 14. This data is found to be consistent with existing data where comparable and lends strong support ot the idea of two separate source populations contributing to the cosmic ray composition.

Maehl, R. C.↗