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All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Nuclear gamma-rays from energetic particle interactions

Gamma-ray line emission due to nuclear deexcitation following energetic particle interactions with abundant constituents of cosmic matter is studied. Reactions induced by energetic protons and alpha particles in ambient nuclei (He, C, N, O, Ne, Mg, Al, Si, S, Ca, and Fe) are considered, along with inverse reactions in which energetic nuclei interact with ambient H and He. Line-production cross sections are evaluated by analyzing a large body of laboratory nuclear data. Both prompt gamma rays, produced by direct excitation of nuclear levels and by spallation reactions that leave the secondary nucleus in an excited state, and delayed emission from long-lived radioactive nuclei also produced in the energetic particle reactions are investigated. A line list is provided, and the shapes of the gamma-ray lines are determined. Gamma-ray line production in the interstellar medium is evaluated in detail.

Ramaty, R.↗
NASA NTRS1979

The auroral ionosphere - Comparison of a time-dependent model with composition measurements

A time-dependent model of the auroral ionosphere including the odd nitrogen species, NO, N(D-2), and N(S-4), is used for comparison with data from a coordinated rocket-satellite measurement of an auroral event. The chemical scheme and the adopted rate coefficients have been shown to be compatible with daytime mid-latitude ionospheric chemistry. The electron flux and neutral atmospheric parameters measured on the satellite are used to compute the appropriate ionization and dissociation rates. The calculated NO(plus), O2(plus), O(plus), Ne, and NO densities agree well with the rocket measurements. The calculated N2(plus) densities are larger than the measured densities by a factor of 3 at most altitudes. The calculations show that the nitric oxide content of the aurora (about 1.2 times 10 to the 9th NO molecules/cu cm at 105 km) is below the saturation value.

Gerard, J.-C.↗
NASA NTRS1979

Tectonic stress in the plates

In the present paper, the basic set of global intraplate stress orientation data is plotted and tabulated. Although the global intraplate stress field is complicated, several large-scale patterns can be seen. Much of stable North America is characterized by an E-W to NE-SW trend for the maximum compressive stress. South American lithosphere beneath the Andes, and perhaps farther east in the stable interior, has horizontal compressive stresses trending E-W to NW-SE. Western Europe north of the Alps is characterized by a NW-SE trending maximum horizontal compression, while Asia has the maximum horizontal compressive stress trending more nearly N-S, especially near the Himalayan front.

Richardson, R. M.↗
NASA NTRS1979

Isotopic anomalies of noble gases in meteorites and their origins. III - LL-chondrites

Nine LL-chondrites were studied by selective etching to characterize the noble gas components in three mineral fractions: HF-HCl-solubles, chromite and carbon. The Ne-20/Ar-36 ratio is considered, noting that chondrites of different petrologic types cannot all be derived from the same volatile rich ancestor, but must have formed over a range of temperatures, with correspondingly different volatile contents. Variations in the carbonaceous chondrite fission (CCFXe) component in LL3, LL5, and LL6 chondrites are discussed, noting that if CCFXe comes from a supernova, then its distribution in LL-chondrites requires three presolar carrier minerals of the right solubility properties, containing three different xenon components. However, if CCFXe comes from fission of a volatile superheavy element, then its decrease from LL3 to LL6 can be attributed to less complete condensation from the solar nebula. Finally, the three types of primordial xenon components which occur in different minerals of the same meteorite are described.

Alaerts, L.↗
NASA NTRS1980

Cosmic ray studies with a gas Cherenkov counter in association with an ionization spectrometer

The results from a balloon-borne gas Cherenkov counter (threshold 16.5 GeV/nucleon) and an ionization spectrometer are presented. The gas Cherenkov counter provides an absolute energy distribution for the response of the calorimeter for 5 or = Z 26 nuclei of cosmic rays. The contribution of scintillation to the gas Cherenkov pulse height was obtained by independently selecting particles below the gas Cherenkov threshold using the ionization spectrometer. Energy spectra were derived by minimizing the chi squared between Monte Carlo simulted data and flight data. Best fit power laws, dN/dE = AE-gamma, were determined for C, N, O, Ne, Mg, and Si. The power laws, all consistent with E (-2.7) are not good fits to the data. A better fit is obtained using the spectrum derived from the spectrometer. The data from the ionization calorimeter and the gas Cherenkov are thus completely self-consistent.

Balasubrahmanyan, V. K.↗
NASA NTRS1975

Atomic emission spectroscopy

The relationship between the Slater-Condon theory and the conditions within the atom as revealed by experimental data was investigated. The first spectrum of Si, Rb, Cl, Br, I, Ne, Ar, and Xe-136 and the second spectrum of As, Cu, and P were determined. Methods for assessing the phase stability of fringe counting interferometers and the design of an autoranging scanning system for digitizing the output of an infrared spectrometer and recording it on magnetic tape are described.

Andrew, K. H.↗
NASA NTRS1979

Carbonaceous chondrites. I - Characterization and significance of carbonaceous chondrite /CM/ xenoliths in the Jodzie howardite

Mineralogical, chemical, textural, and isotopic studies of the abundant carbonaceous inclusions in the Jodzie howardite which are consistent with carbonaceous chondrite (CM) characteristics are examined. These CM xenoliths show regolith alteration comparable to the Murray and Murchison meteorites but less than Nogoya, flow-oriented development of phyllosilicates and 'poorly characterized phases', and partial oxidation of sulfides. Temperature-programmed pyrolysis mass spectrometry indicates that gas release patterns of volatiles and hydrocarbons, and N, C, and S contents are typical of CM meteorites. The fact that the Ne content is typical for 'solar' values and the isotopic structure of Xe is 'planetary' indicates that these gases were entrapped by different mechanisms, and cosmic ray exposure ages for the xenoliths agree with the reported exposure age for the eucritic host.

Bunch, T. E.↗
NASA NTRS1979

Infrared spectra of IC 418 and NGC 6572

Spectrophotometric observations from 2 to 4 and 8 to 13 microns of NGC 6572 and from 4 to 13 microns of IC 418 are reported. Also reported are observations of the size of IC 418 in the optical and at 1.65 and 2.2 microns. Both planetary nebulae emit more radiation than expected from recombination at wavelengths longer than -4 microns; this radiation is attributed to heated dust. The spectra show a plateau from 10.5 to 13 microns, and this peak is tentatively attributed to emission from large silicon carbide particles. Fine-structure emission lines are also discussed; the presence of (forbidden Ar III) but not (forbidden Ne II) in NGC 6572 suggests that ions having the same ionization potential can nevertheless have different fractional abundances.

Willner, S. P.↗
NASA NTRS1980

High resolution measurements of galactic cosmic-ray neon, magnesium, and silicon isotopes

High-resolution measurements of the abundances of individual isotopes of neon, magnesium and silicon in galactic cosmic rays are reported. The Caltech Heavy Isotope Spectrometer Telescope on board the ISEE 3 spacecraft was used to obtain measurements in the range 30 to 180 MeV/n at an rms mass resolution of 0.20 amu. Results indicate excesses of Ne-22 as well as Mg-25 and Mg-26 in galactic cosmic rays with respect to their solar system abundances. Calculations of the effects of interstellar propagation and solar modulation on cosmic-ray isotope abundances also imply an Mg-25 + Mg-26 cosmic ray source fraction significantly greater than the solar system fraction, and it is suggested that the cosmic ray source material and solar system material were synthesized under different conditions.

Mewaldt, R. A.↗
NASA NTRS1980

The soft X-ray polychromator for the Solar Maximum Mission

The paper considers the soft X-ray polychromator (XRP) operating in the 1.4-22.4 A range of the soft X-ray spectrum which includes many emission lines important for the diagnosis of plasmas in the 1.5-50 million deg temperature range. The flat crystal scanning spectrometer provides for a channel polychromatic mapping of flares and active regions in the resonance lines of O VIII, Ne IX, and Mg XI; in its spectral scanning mode it covers essentially the entire 1.4-22.5 A region.

Acton, L. W.↗
NASA NTRS1980

'Bottleneck' calculation of ion-electron recombination coefficients for lithium-like ions

The ion-electron recombination coefficients for the lithium-like ions C IV, O VI, Ne VIII, Si XII and Ar XVI are computed by the bottleneck method of Byron et al. (1962). In this method, the minimum rate of transitions down the ladder of energy level is taken as the limiting recombination rate, and the particular energy level corresponding to the minimum transition rate is found. The partial collisional radiative recombination coefficient is obtained in terms of the equilibrium population, the rate of collisional de-excitation, the mean radiative transition probability from the bottleneck level and the total transition probability from a level above the bottleneck level to all levels below it. The full collisional-radiative recombination is then obtained by the addition of the values of the radiative recombination coefficient and the three-body recombination coefficient to the ground level. Results of the calculation are shown to be in good agreement with those of Drawin and Emard (1975) for the case of hydrogen. It is also noted that the process of dielectronic recombination, which is not accounted for here, may be significant at lower densities.

Kastner, S. O.↗
NASA NTRS1980

Spatial distribution of XUV emission and density in a loop prominence

The spatial distribution of XUV emission in the 14 August, 1973 loop prominence observed with the NRL spectroheliograph on Skylab is studied. The loop prominence consists of two large loops and is observed in lines from ions with temperatures ranging from 50,000 to 3,000,000 K. The loops seen in low temperature lines such as from He II, Ne VII, Mg VII, Mg VIII, and Si VIII are systematically displaced from loops seen in higher temperature lines such as from Si XII, Fe XV, and Fe XVI. The cross section of the loop, particularly in cooler lines is nearly constant along the loop. For hotter loops in Si XII, Fe XV, and Fe XVI, however, emission at the top of the loop is more intense and extended than that near the footpoints, which makes the loops appear wider at the top. The observed spatial displacement between cooler and hotter loops suggest that the 14 August loop prominence is composed of many magnetic flux tubes, each with its own temperature.

Cheng, C.-C.↗
NASA NTRS1980

Laser measurement of extinction coefficients of highly absorbing liquids

A coaxial dual-channel laser system has been developed for the measurement of extinction coefficients of highly absorbing liquids. An empty wedge-shaped sample cell is first translated laterally through a He-Ne laser beam to measure the differential thickness using interference fringes in reflection. The wedge cell is carefully filled with the oil sample and translated through the coaxially positioned dye laser beam for the differential attenuation or extinction measurement. Optional use of the instrumentation as a single-channel extinction measurement system and also as a refractometer is detailed. The system and calibration techniques were applied to the measurement of two crude oils whose extinction values were required to complete the analysis of airborne laser data gathered over four controlled spills.

Hoge, F. E.↗
NASA NTRS1980

Forbidden lines of np/q/ ions. I - Detailed balance and line intensity ratios

The detailed balance equations are solved in the ground state terms of 37 ions of C, N, O, Ne, Mg, Si, S and Fe; atomic data for 235 transitions of these ions are tabulated, and 14 line ratios of q = 2,4 ions and eight line ratios of q = 3 ions are graphed. Forbidden emission lines of these ions are in the far and near UV, visible, and near and far IR regions of the spectrum. In addition, detailed calculations of the relative populations of the levels of the ground state are presented as a function of temperature and density.

Kafatos, M.↗
NASA NTRS1980

Spectra from nuclear-excited plasmas

The paper discusses the spectra taken from He-3(n,p)H-3 nuclear-induced plasmas under high thermal neutron flux, lasing conditions. Also, initial spectra are presented for U-235F6 generated plasmas. From an evaluation of these spectra, important atomic and molecular processes that occur in the plasma can be inferred. The spectra presented are the first to be generated by He-3 and U-235F6 nuclear reactions under high neutron flux, lasing conditions. The U-235(n,ff)FF reaction, which liberates 165 MeV of fission-fragment kinetic energy, creates plasmas that are of great interest, since at sufficiently high densities of U-235F6 the gas becomes self-critical; thus, there is no need for an external driving reactor (source of neutrons). The spectra from mixtures of He-3 and Ar, Xe, Kr, Ne, Cl2, F2 and N2 indicate little difference between high-pressure nuclear-induced plasmas and high-pressure electrically pulsed afterglow plasmas for noble-gas systems

De Young, R. J.↗
NASA NTRS1979

Einstein observations of the X-ray structure of Centaurus A - Evidence for the radio-lobe energy source

The X-ray source at the center of the radio galaxy Centaurus A has been resolved into the following components with the imaging detectors on board the Einstein X-ray Observatory: (1) a point source coincident with the infrared nucleus; (2) diffuse X-ray emission coinciding with the inner radio lobes; (3) a 4-arcmin extended region of emission about the nucleus; and (4) an X-ray jet between the nucleus and the NE inner radio lobe. The 2 x 10 to the 39th ergs/s detected from the radio lobes probably arises from inverse Compton scattering of the microwave background. The average magnetic field in the SW lobe is determined to be not less than 4 microgauss. The extended region may be due to emission by a cloud of hot gas, cosmic-ray scattering, or stellar sources. The jet provides strong evidence for the continuous resupply of energy to the lobes from the nucleus.

Schreier, E. J.↗
NASA NTRS1980

Cosmic ray studies with a gas Cerenkov counter in association with an ionization spectrometer

The results from a balloon-borne gas Cerenkov counter (threshold 16.5 GeV/nuc) and an ionization spectrometer are presented. The gas Cerenkov counter provides an absolute energy calibration for the response of the calorimeter for the Z range of 5-26 nuclei of cosmic rays. The contribution of scintillation to the gas Cerenkov pulse height has been obtained by independently selecting particles below the gas Cerenkov threshold using the ionization spectrometer. Energy spectra were derived by minimizing the chi-squared between a Monte Carlo simulated data and flight data. Best fit power laws were determined for C, N, O, Ne, Mg, and Si. The power laws, all consistent with E exp-2.7, are not good fits to the data. A better fit is obtained using the spectrum derived from the spectrometer.

Balasubrahmanyan, V. K.↗
NASA NTRS1980

Physical properties of individual coronal loops in a solar active region observed in the XUV

The physical properties of individual coronal loops in a solar active region observed in the XUV by the slitless objective grating spectroheliograph on board Skylab are investigated. Spectroheliograms of the normal active loop region McMath 12378 reveal three distinctive structural groups of loops in different temperature ranges, namely (1) small compact and smaller loops at temperatures of about 2,000,000 K observed in Fe XV and Fe XVI; (2) large Ne VII and Mg IX loops at temperatures from 500,000 to 1,000,000 K; and (3) chromospheric ribbons in He II and H alpha. The temperature of the active region is found to be uniform at about 2,000,000 K in the loops and background while loop density is found to be 3.5 x 10 to the 9th/cu cm in the loops and 2.5 x 10 to the 9th/cu cm in the surrounding background. Significant changes in the active region are observed in 24 h, although the gross temperature density structures of many loops do not show changes in 7 min. Gas pressure within the coronal loops is found to be about 40% greater than that of the background plasma. The observed loop parameters are noted to be consistent with flux-limited models of density enhancement in magnetic flux tubes and thus no esoteric heating function is required.

Cheng, C.-C.↗