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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Acceleration of H, He, and heavy ions observed in the magnetosheath, magnetotail, and near-by interplanetary space

Pulses of electrons and ions composed of H, He, and heavier elements were observed in the magnetosheath, magnetotail, and near-by interplanetary space. From the spatial positions where these particles were detected and the ion flow directions, it is concluded that they were accelerated at the bow shock near the sub-solar point and in the near-earth region of the neutral sheet of the magnetotail.

Fan, C. Y.↗
NASA NTRS1976

Storage and recombination of atomic H in solid H2

A phenomenological rate process theory is developed for the storage and rapid recombination of atomic hydrogen free radicals in a crystalline molecular hydrogen solid at temperatures in the range of about 0.1-4 K. It is shown that such a theory can account quantitatively for the recently observed dependence of the storage time on the storage temperature, for the maximum concentration of trapped H atoms, and for the time duration of the energy release in the tritium decay experiments of Webeler. The theory predicts that maximum atomic hydrogen concentrations of the order 10 to the 20th per cu cm are realizable for storage temperatures in the vicinity of 0.14 K.

Rosen, G.↗
NASA NTRS1977

Geologic investigation of Mercury data and the subsequent mapping and explanation of the quadrangle area H-12

The origin of scraps and ridges mapped in the H-12 region of Mercury are discussed. These features apparently are of non-impact origin and show distinctly non-random patterns of distribution and orientation. These patterns cannot be simply related to selective enhancement of visibility by lighting conditions, global stresses of spin down or interior cooling, or local uplifts or subsidences. Suggestions are made that the origin of these structures may lie outside the region of Mercury photographed or the scarps and ridges may have formed by reactivation of faults or joints bounding pre-existing crystal blocks.

Blasius, K. R.↗
NASA NTRS1976

The abundances of H-3 and C-14 in the solar wind

Tritium is measured as a function of depth in a Surveyor 3 sample. The upper limit for solar-wind-implanted tritium gives a H-3/H-1 limit for the solar wind of 1 part in one hundred billion. The temperature release patterns of C-14 from lunar soils are measured. The C-14 release patterns from surface soils differ from a trench-bottom soil and give evidence for the presence of C-14 in the solar wind with a C-14/H-1 ratio of approximately 4 parts in one hundred billion. The implications of these radionuclide abundances in the solar wind are discussed.

Fireman, E. L.↗
NASA NTRS1976

Emission nebulae in the Magellanic Clouds. I - The H II regions

A review of optical and radio studies of the H II regions in the Magellanic Clouds is presented. Recent studies are emphasized, particularly optical studies of the kinematics, spectra, and chemical composition. The implications of the studies for the understanding of the evolution of stars and galaxies in general, and the Magellanic Clouds in particular, are noted. Suggestions for future work are also given.

Dufour, R. J.↗
NASA NTRS1976

2-4 micron spectrophotometric observations of compact H II regions

Spectrophotometric observations from 2 to 4 microns of the compact H II regions W51-IRS 2, K3-50, and NGC 7538 are reported. Spectral features observed include hydrogen recombination lines and an absorption attributed to interstellar ice. Extinctions to the various sources are derived based on the observed hydrogen lines and radio fluxes. Thermal dust emission is found to dominate free-free and bound-free emission for wavelengths not less than 2 microns. The ice absorption is analyzed and compared with the extinction and 10 microns silicate absorption. A 3.3 micron emission feature (potentially due to the same material as in NGC 7027) was observed.

Soifer, B. T.↗
NASA NTRS1977

Infrared studies of H II regions and dust clouds near K3-50

Ground-based infrared observations of the K3-50 region are reported at wavelengths between 2 and 34 microns as well as at 1 mm. The main results are that (1) the visible nebular K3-50 is displaced from its infrared and radio counterparts; (2) component Cl (the OH source ON-3) appears very faint at wavelengths not exceeding 20 microns and is therefore probably obscured by several hundred magnitudes of visual extinction; (3) both K3-50 and component C are associated with separate condensations of molecular hydrogen, each of about 3000 solar masses; and (4) there are no strong sources in this region at 20 microns other than those associated with H II condensations.

Wynn-Williams, C. G.↗
NASA NTRS1977

Far-infrared spectrometry of H II regions and the Galactic Center

The H II regions W3, M17, and W51, as well as the Galactic center regions Sgr A and Sgr B2, were observed at a spectral resolving power of roughly 15 in the range from 45 to 115 microns. At that resolution the spectra appear featureless and can be approximated by dilute blackbody curves whose temperatures range from approximately 90 K down to about 40 K.

Ward, D. B.↗
NASA NTRS1977

Stability of the equilibrium for atomic H in solid H2

The previously reported phenomenological rate process theory for the storage of atomic hydrogen free radicals in a tritium-impregnated crystalline molecular hydrogen solid is used to determine the dynamical stability of the constant uniform equilibrium solution. The analysis indicates that the equilibrium is unstable (thus, unattainable experimentally) for storage temperatures in a certain range (specifically between 0.134 and 0.80 K for 0.03% tritium by weight, and between 0.165 and 0.80 K for 1.20% tritium by weight), while being absolutely stable with respect to arbitrary small-amplitude perturbations for all storage temperatures below and above this range. The theory also predicts the maximum size for a stable H/H2 sample with an appreciable concentration of trapped H and a net excess rate of volumetric heating due to the tritium decay.

Rosen, G.↗
NASA NTRS1977

Measurements of H-beta, He D3, and Ca/+/ 8542-A line emission in quiescent prominences

Measurements of H-beta, He D3, and Ca(+) 8542-A line emission in 18 quiescent prominences are presented which were performed with a 25-cm coronagraph/coude spectrograph system and an optical multichannel analyzer utilizing a Si-vidicon detector assembly mounted at the single-pass spectrograph port. The data obtained show that the line profiles deviate in the wings from those calculated on the basis of an isothermal atmosphere and a Gaussian absorption coefficient. Both a non-Gaussian microturbulence component and a temperature gradient from prominence-core to coronal values can successfully account for this phenomenon. The line widths from a given line of sight of prominence material are reduced on the basis of a common core emitting region with a temperature of 7500 to 11,600 K and a microturbulent velocity of 4.5 to 7.1 km/s for the isothermal model (these values are 5% to 10% less for the two-temperature model). It is noted that long-period low-amplitude oscillations in the D3 line width and intensity were observed when a specific line of sight in a quiescent prominence was followed. These oscillations are found to remain coherent for as many as 3 or 4 cycles and to be associated with prominence structural activation.

Landman, D. A.↗
NASA NTRS1978

The 51.8 micron (0 3) line emission observed in four galactic H 2 regions

The (0 III) 51.8 microns line from four H II regions, M42, M17, W51 and NGC 6375A was detected. Respective line strengths are 7 x 10 to the minus 15 power, 1.0 x 10 to the minus 14 power, 2.1 x 10 to the minus 15 power and 2.6 x 10 to the minus 15 power watt cm/2. Observations are consistent with previously reported line position and place the line at 51.80 + or 0.05 micron. When combined with the 88.35 microns (0 III) reported earlier, clumping seems to be an important factor in NGC 6375A and M42 and to a lesser extent in W51 and M17. The combined data also suggest an (0 III) abundance of approximately 3 x 0.0001 sub n e' a factor of 2 greater than previously assumed.

Melnick, G.↗
NASA NTRS1979

Observed distribution functions of H, He, C, O, and Fe in corotating energetic particle streams: Implications for interplanetary acceleration and propagation

Distribution functions for H, He, C, O, and Fe derived from our IMP 8 measurements of approximately 0.15 to approximately 8 MeV/nucleon particles in three corotating streams observed near earth are shown to have a simple exponential dependence on the particle speed. The e-folding speed, v sub o, is typically 0.01c, is found to be the same for the distribution functions of all elements examined, and varies little from one corotating event to the next. The relative abundances of energetic particles in these events resemble most closely the solar coronal composition and, thus, presumably that of the solar wind. These results may imply that the acceleration of these particles, which occurs in corotating interaction regions at several AU from the sun, is by a statistical process.

Gloeckler, G.↗
NASA NTRS1979

51.8 micron forbidden O III line emission observed in four galatic H II regions

The 51.8-micron forbidden O III line has been detected in four H II regions: M42, M17, W51, and NGC 6357A. The respective line strengths are 7 x 10 to the -15th, 1.0 x 10 to the -14th, 2.1 x 10 to the -15th, and 2.6 x 10 to the -15th W/sq cm. The observations are consistent with a previously reported line position and place the line at 51.80 + or - 0.05-micron. When combined with the 88.35-micron forbidden O III observations reported earlier, clumpiness is found to be an important factor in NGC 6357A and M42 and nonnegligible in W51 and M17. The combined data also suggest an O III abundance of about 0.0003 times the electron density, which is a factor of 2 greater than a number of investigators have reported.

Melnick, G.↗
NASA NTRS1978

H Lyman-alpha emission from photodissociation of H2O

Lyman-alpha fluorescence measurements were used to study the photodissociation of water vapor to produce H(n equals 2) atoms from threshold to 500 A. The experimental threshold of 813.0 A nearly coincides with the thermodynamic limit. Excitation cross sections rise slowly from threshold to a maximum value of (1.55 plus or minus 0.12) x 10 to the -18th sq cm at about 709 A and decrease to a negligible value below 550 A. Structure in the excitation function is attributed to predissociation of Rydberg series converging to the B(overbar)B2 state of H2O(plus).

Mentall, J. E.↗
NASA NTRS1979

Observed distribution functions of H, He, C, O, and Fe in corotating energetic particle streams - Implications for interplanetary acceleration and propagation

Distribution functions for H, He, C, O, and Fe derived from our IMP 8 measurements of about 0.15 to 8 MeV per nucleon particles in three corotating streams observed near Earth are shown to have a simple exponential dependence on the particle speed. The e-folding speed, typically 0.01c, is found to be the same for the distribution functions of all elements examined, and varies little from one corotating event to the next. The relative abundances of energetic particles in these events resemble most closely the solar coronal composition and thus, presumably, that of the solar wind. These results may imply that acceleration of these particles, which occurs in corotating interaction regions at several AU from the sun, is by a statistical process.

Gloeckler, G.↗
NASA NTRS1979

Empirical studies of solar flares: Comparison of X-ray and H alpha filtergrams and analysis of the energy balance of the X-ray plasma

The physics of solar flares was investigated through a combined analysis of X-ray filtergrams of the high temperature coronal component of flares and H alpha filtergrams of the low temperature chromospheric component. The data were used to study the magnetic field configuration and its changes in solar flares, and to examine the chromospheric location and structure of X-ray bright points (XPB) and XPB flares. Each topic and the germane data are discussed. The energy balance of the thermal X-ray plasma in flares, while not studied, is addressed.

Moore, R. L.↗