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At least 955 records · Page 53
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NASA NTRS1977

Rate constants for reactions of ClO/x/ of atmospheric interest

Chemical kinetics measurements on 82 gas phase reactions of chlorine containing species are reviewed. Recommended rate constants are given. The principal species of interest are Cl, Cl2, ClO, Cl2O, ClOO, OClO, CINO, HCl and halo derivatives of methane and ethane. Absorption spectra are given for 21 species. In addition the chemical kinetics methods used to obtain these data are discussed with regard to their applicability and reliability.

Watson, R. T.↗
NASA NTRS1978

A new, compact far-infrared source in the W31 region

In a survey of the W31 region, a compact far-infrared source was detected at the position of the radio continuum source G 10.6-0.4. Associated with this infrared source and in close coincidence with its position is an H II region with a compact core and extended halo as well as OH and H2O masers. An extended molecular cloud, centered on these sources, has also been detected. The compact source and associated masers may be located at the H II region-molecular-cloud interface in a thin shocked layer of neutral gas driven into the molecular cloud by the expansion of the H II region. The compact H II region is depleted of dust and must be surrounded by a very dense shell of dust and gas (hydrogen number density in excess of 200,000 per cu cm). The source probably represents an early stage of stellar evolution.

Fazio, G. G.↗
NASA NTRS1978

Solar wind stream interfaces

Results are presented for a superposed epoch analysis of discontinuous solar wind interfaces. The average time-space profiles of stream interfaces are discussed with reference to fluid properties (flow speed, pressure ridge, density, electron and proton temperatures) and kinetic properties (electron core and halo, flow speed fluctuations, electron heat flux, alpha particles). Other aspects of stream interfaces are described, such as the persistence of individual interfaces, shock associations, the sector boundaries of the interplanetary magnetic field, and sudden impulses in the geomagnetic field. Interface position is considered in terms of the observed temperature jump. A conceptual model of high-speed stream evolution is proposed.

Gosling, J. T.↗
NASA NTRS1978

Structure and evolution of solar radio bursts at 26.4 MHz

Results are reported for multiple-baseline interferometric measurements of type II, III, IV, and V solar radio bursts at 26.4 MHz. Thirty-two burst events in a two-month period are analyzed by fitting a double-Gaussian two-dimensional source-brightness distribution model to the observed interferometer visibility function. The multibaseline time-sharing interferometer system employed is described in detail, the model-fitting technique is outlined, and values of the model-fit parameters are given for all 32 cases, which include two type II bursts, three type IV bursts, 17 type III bursts, seven type V bursts, and three bursts of type III, V pairs. The temporal evolution of source structure, size, and motion is examined for the different burst types. The core-halo source structure for the type III bursts is interpreted in comparison to two models, one of which assumes scattering and refraction of a point source while the other postulates primarily refraction from an ensemble of sources distributed over a wide sector in solar longitude.

Chen, H. S.-L.↗
NASA NTRS1978

Some astrophysical consequences of the existence of a heavy stable neutral lepton

It is suggested that a stable, massive, neutral lepton may dominate the present mass density in the universe. To investigate this assumption, attention is given to an analysis of extended gauge theories as they apply to a lepton with a mass of a few GeV/sq cm. A critical factor in the accuracy of the hypothesis is the actual mass of the lepton, and it is noted that the more massive the individual particle, the smaller the particle's aggregate contribution to the universal mass density. High energy accelerators could prove a useful tool in an empirical determination of the lepton's mass. It is further suggested that the lepton considered might provide the material in galactic halos, or supply the mass necessary to bind galactic clusters. A study of intergalactic annihilation radiation is expected to yield more data pertaining to the lepton's existence.

Gunn, J. E.↗
NASA NTRS1978

Absorption in the spectra of quasi-stellar objects and BL Lacertae objects

Observations of absorption in the spectra of 64 QSOs and two BL Lac objects are reviewed. Criteria for selecting the absorption-line objects are discussed along with line identifications, properties of identified absorption systems, the observed absence of variability in the absorption lines, the redshift distribution, line locking, and absorption shortward of the Lyman limit. The possibility of noncosmological redshifts is noted, and two interpretations of the absorption-line data are considered: (1) the 'intrinsic' hypothesis that the absorptions arise in gas associated with the QSOs and (2) the 'intervening' hypothesis that they are produced by intervening galaxies, galactic halos, or intergalactic clouds intersected by the line of sight to a QSO. Direct observational tests for the location of the absorbing hydrogen in several individual objects are described. It is concluded that no conclusive observational evidence exists which is capable of establishing whether the absorption is intrinsic or intervening.

Perry, J. J.↗
NASA NTRS1978

A study of the absorption-line spectra of six high-redshift quasi-stellar objects

High-resolution spectrograms of six QSOs with apparent visual magnitudes of 17.0 to 18.5 and redshifts greater than 2 are studied for absorption lines. Accurate wavelengths are measured for all the absorption lines that could be detected, attempts are made to identify redshift systems, and the redshifts in each object are examined. Analysis of the absorption-line spectra shows that: (1) a large number of redshifts covering a wide range of values are present in five of the QSOs; (2) about two-thirds of the absorption lines remain unidentified, cannot be of Galactic origin, and are not associated with existing redshift systems; (3) many comparatively small absorption redshifts exist which, if they are due to intervening galaxies, must be produced by very large halos; and (4) in one QSO there is a possible redshift system containing five lines with an absorption redshift that is significantly greater than the emission redshift.

Roberts, D. H.↗
NASA NTRS1978

On the origin of the absorption spectra of quasi-stellar and BL Lacertae objects

The possibility is reexamined that multiple absorption spectra of QSOs are due to gas in the disks, coronae, or halos of intervening galaxies. Using the same catalog and parameters as Burbidge et al. (1977) but assuming that the cosmological constant is approximately equal to the critical value instead of equal to zero, it is found that the discrepancy of several orders of magnitude between the predicted and observed multiplicities reported by Burbidge et al. (1977) is drastically reduced and that the observed multiplicity distribution is theoretically obtainable. The intervening-galaxy hypothesis cannot be rejected on the basis of this test.

Canuto, V.↗
NASA NTRS1978

Space plasma laboratory - Experiment in simulated ionospheric plasma

Several experiments with simulated ionospheric plasma were performed in the Johnson Space Center's large (17 m diameter x 27 m height) vacuum chamber. Two of these, the RF discharge and the electron-beam plasma discharge, are described here. The RF experiment involved measurement of the loading on a 5 m dipole and a 5 m loop antenna caused by the presence of a plasma. The results indicate that when the RF frequency is near the electron gyro frequency a self-sustained plasma discharge is set up and the real part of the complex antenna impedance increases. The beam-plasma experiment was carried out to study a discharge produced by an electron beam with an energy of about 1 keV when the electron beam was injected parallel to the ambient magnetic field. As the beam current was raised to a critical level, a spontaneous transition occurred whereby a luminous halo was formed around the electron beam indicating a sustained discharge.

Konradi, A.↗
NASA NTRS1978

Characteristic electron variations across simple high-speed solar wind streams

The paper deals with electron variations across simple high-speed streams. Comprehensive scans of the shapes of electron distributions measured at the highest bulk speeds confirm the results of Rosenbauer et al. (1976, 1977) and show that the electron velocity distributions can be broken down into a low-energy or core component and a high-energy strongly beamed component. The low-energy component displays many characteristics expected from a fluid: the internal particle coupling necessary to maintain this state must result from both binary Coulomb collisions and wave-particle interactions. The high-energy or halo component displays many characteristics expected to develop in the absence of collisions beyond a certain base radius. These electrons appear to evolve under the primary influence of static interplanetary magnetic and electric fields and, therefore, develop very anisotropic velocity distributions.

Feldman, W. C.↗
NASA NTRS1978

On the contribution of normal galaxies to the diffuse X-ray background

A calculation has been made of the contribution of normal galaxies to the diffuse X-ray background, based on a model of the X-ray luminosity evolution of galaxies in which two populations of galactic X-ray sources are distinguished. With plausible estimates of the behavior of the galactic X-ray source populations with time, normal galaxies provide between 1.5% and 9% of the X-ray background between 2 and 10 keV. Unless massive halos exist around galaxies and their formation is accompanied by the production of early-type Population I X-ray binaries, a firm upper limit of about 25% can be set on the contribution of normal galaxies to the X-ray background between 2 and 10 keV.

Van Paradijs, J.↗
NASA NTRS1979

Optical measurement in the middle atmosphere

The paper describes the optical measurement of atmospheric trace gases by outlining various sensing techniques and general problems encountered in remote or in situ optical measurement. The review encompasses discussions of observational approaches, geometry and platforms, instrumentation, atmospheric absorption bands, and some analyses of observed data. Some future global experiments, including Nimbus G, Spacelab I, HALOE, and MAPS, are briefly discussed.

Park, J. H.↗
NASA NTRS1979

Acceleration and transport of galactic cosmic rays

A recently proposed cosmic-ray acceleration mechanism is combined with a model of transport and loss from the Galaxy to construct a model for galactic cosmic rays. Various aspects of the cosmic-ray spectrum, including the secondary-to-primary ratio as a function of energy, are found to fit naturally into the overall picture. A solution to the dynamical-halo model with energy-dependent diffusion coefficient (kappa) is presented. This model is consistent with the observed spectra if kappa is proportional to the square root of the kinetic energy. The observed flattening of the secondary-to-primary ratio below about 1-2 GeV per nucleon is shown to be a natural consequence of the model. Similarly, the primary electron spectrum is predicted to flatten below about 1-2 GeV, which is consistent with deconvolution of the local nonthermal radio spectrum, although the flattening is not quite as much as indicated by the observations.

Jokipii, J. R.↗
NASA NTRS1979

Proton-driven electromagnetic instabilities in high-speed solar wind streams

Electromagnetic instabilities of the field-aligned, right-hand circularly polarized magnetosonic wave and the left-hand circularly polarized Alfven wave driven by two drifted proton components are analyzed for model parameters determined from Imp 7 solar wind proton data measured during high-speed flow conditions. Growth rates calculated using bi-Lorentzian forms for the main and beam proton as well as core and halo electron velocity distributions do not differ significantly from those calculated using bi-Maxwellian forms. Using distribution parameters determined from 17 measured proton spectra, we show that considering the uncertainties the magnetosonic wave may be linearly stable and the Alfven wave is linearly unstable. Because proton velocity distribution function shapes are observed to persist for times long compared to the proton gyroperiod, the latter result suggests that linear stability theory fails for proton-driven ion cyclotron waves in the high-speed solar wind.

Abraham-Shrauner, B.↗
NASA NTRS1978

The spectrum of cosmic electrons with energies between 6 and 100 GeV

Final results are reported concerning the spectrum of 6-100-GeV cosmic-ray electrons observed during a balloon exposure of approximately 3500 sq m-s-sr at an average depth of 4.8 g/sq cm. The spectral intensity of primary cosmic-ray electrons is found to have a power-law dependence on electron energy with an index of 3.4 + or - 0.1; the ground-level spectrum of secondary cosmic-ray electrons is also shown to be a power-law spectrum, but with an index of 2.9 + or - 0.1. The observed spectrum, which is significantly steeper than the nuclear spectrum, is interpreted as a fully steepened one reflecting an equilibrium between injection and energy loss. It is suggested that the confinement volume for cosmic rays extends beyond the galactic disk and includes a halo of reduced gas density where the Compton-synchrotron mechanism operates but the probability of nuclear interactions is small.

Meegan, C. A.↗
NASA NTRS1978

Cosmic electrons, galactic radio background and cosmic ray confinement

Cosmic ray electron measurements and radio background data are analyzed to obtain bounds on the galactic magnetic fields. It is shown that the magnetic field required to explain the radio flux must be greater than 2 micro Gauss. The difference in the steepening of the radio spectra towards the Anticenter and the Halo Minimum provides evidence that the magnetic field decreases with the height above the galactic plane. The calculations of Bulanov and Dogiel (1975) are applied to the radio and electron observations. It is shown that the most plausible interpretation of these results requires that the electron injection spectrum has an intrinsic flattening below a few GeV. The observed steepening of radio and electron data is apparently a combined effect of the injection spectrum and the first break due to continuous energy loss of electrons in space.

Badhwar, G. D.↗
NASA NTRS1980

X-ray optical properties of a Wolter telescope

Physical properties and the fabrication sequence of a Wolter telescope are discussed. Such telescopes are intended to examine the dust scattering halos after being placed in orbit by a booster rocket launched from Australia.

Ondrusch, A.↗