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  • ASTROPHYSICS  (432)
  • GEOPHYSICS  (431)
  • 1995-1999
  • 1985-1989
  • 1980-1984
  • 1975-1979  (863)
  • 1940-1944
  • 1977  (863)
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  • 1995-1999
  • 1985-1989
  • 1980-1984
  • 1975-1979  (863)
  • 1940-1944
Year
  • 1
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    Kerogen structures in recently-deposited algal mats at Laguna Mormona, Baja California: A model system for the determination of kerogen structures in ancient sediments (1977)
    In:  CASI
    Details
    Publication Date: 2005-02-28
    Keywords: GEOPHYSICS
    Type: Res. in the Space Sci., Vol. 2, No. 1; 29 p
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  • 2
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    Gamma rays, cosmic rays, and galactic structure (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Observations of cosmic and gamma radiation by SAS-2 satellite are summarized and analyzed to determine processes responsible for producing observed galactic radiation. In addition to the production of gamma rays in discrete galactic objects such as pulsars, there are three main mechanisms by which high-energy (greater than 100 MeV) radiation is produced by high-energy interactions involving cosmic rays in interstellar space. These processes, which produce what may be called diffuse galactic gamma-rays, are: (1) the decay of pi mesons produced by interactions of cosmic ray nucleons with interstellar gas nuclei; (2) the bremsstrahlung radiation produced by cosmic ray electrons interacting in the Coulomb fields of nuclei of interstellar gas atoms; and (3) Compton interactions between cosmic ray electrons and low-energy photons in interstellar space.
    Keywords: ASTROPHYSICS
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 315-346
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  • 3
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    Gamma rays and large scale galactic structure (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Gamma ray astronomy is now beginning to provide a new look at the galactic structure and the distribution of cosmic rays, both electrons and nucleons, within the galaxy. The observations are consistent with a galactic spiral-arm model in which the cosmic rays are linearly coupled to the interstellar gas on the scale of the spiral arms. The agreement between the predictions of the model and the observations for regions of the plane where both 21-cm and 2.6-mm CO surveys exist emphasizes the need to extend these observations to include the entire plane. Future gamma-ray observations with more sensitivity and better angular resolutions, combined with these radio surveys, should shed new light on the distribution of cosmic rays, the nature of the galaxy, and the location and intensity of the spiral arms.
    Keywords: ASTROPHYSICS
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 301-314
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  • 4
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    Galactic distribution of pulsars (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived, using a uniform sample of pulsars detected during a 408-MHz pulsar survey at Jodrell Bank. There are indications of a fine-scale structure in the spatial distributions and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in our galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy has been estimated and used to derive the pulsar birthrate.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 265-282
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  • 5
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    Gamma rays and supernova explosions (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Thermal radiation associated with the explosion of supernovae is investigated. High temperature is required to produce copious gamma radiation of this sort. It appears that type 11 supernovae do not release much of their energy as gamma ray continuum radiation.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 257-264
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  • 6
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    Remarks on the overall distribution of hydrogen in the galactic disk (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The degree of saturation characterizing low altitude emission observations of H(I) and the optical depth corrections to the derived column and volume densities are discussed. The amount of fine-scale velocity and spatial structure diluted by the instrumental limitations of the presently available surveys are described. The general problem of detailed mapping of H(I) in the galaxy is explored. Comparison is made between the distribution of H(I) and that of CO and several other galactic tracers. Atomic hydrogen is unique in its distribution, instead of being typical of many Population I constituents. As defined by atomic hydrogen, the galactic disk has a diameter fully twice as large as that defined by the ionized and molecular states of hydrogen, as well as by other molecules, supernova remnants, pulsars, gamma-radiation, synchroton radiation, and the youngest stars. It is also less confined to the galactic equator than most of the other constituents. The degree of small scale structure apparent in the molecular observations is much greater than that in the H(I) observations.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 163-188
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  • 7
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    Gamma ray pulsars (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 109-118
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  • 8
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    Radiation mechanisms and magnetospheric structure of pulsars (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Considerations made in developing a model of pulsars are explored. Observational data seems to support the argument that pulsar magnetospheres may contain large masses of plasma. The cascade process resulting from pair creation enables one to interpret the X-ray emission from the Crab and Vela pulsars as synchrotron radiation. On the other hand, the optical radiation from the Crab pulsar is best understood as coherent curvature radiation. Radio emission is interpreted as curvature radiation produced by charge bunches moving along magnetic-field lines. Certain tests of this model are proposed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 99-108
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  • 9
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    Experience with the inversion of Nimbus 4 BUV measurements to retrieve the ozone profile (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: The relative merits of pressure increment and partial derivative formulations of the ozone inversion problem are discussed briefly. The height range of validity of the retrieved ozone profile and the effects of adding wavelengths to or of dropping wave-length from the inversion system are indicated. Illustrative results are presented for profiles retrieved from BUV data using Backus-Gilbert, minimum information (Twomey), and quasi-optimum procedures.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 577-597
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  • 10
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    The inversion of stratospheric aerosol and ozone vertical profiles from spacecraft solar extinction measurements (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: The inversions of multi-channel solar extinction measurements have been analyzed for the 0.35-1.0 micron wavelength region to retrieve stratospheric aerosol and ozone vertical profiles using both the constrained linear inversion scheme and the iterative scheme. The inversions of the multi-wavelength solar extinction data obtained from spacecraft have been analyzed based on the inversion of computer simulated data using various atmospheric models with differing amounts of aerosol and ozone in the stratosphere. The sensitivities of the inversion schemes to different experimental errors are discussed in terms of accuracy and resolution of the retrieved profiles.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 505-527
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  • 11
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    Application of modified Twomey techniques to invert lidar angular scatter and solar extinction data for determining aerosol size distributions (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: Polarization properties of the angularly scattered laser light from a volume of air are used to determine the size distribution of the aerosol particles within the volume by the use of appropriate inversion techniques. Similar techniques are employed to determine a mean size distribution of the particulates within a vertical column through the atmosphere from determinations of the aerosol optical depth as a function of wavelength. In both of these examples, a modification of an inversion technique originally described by Twomey has been employed. Details of this method are presented as well as results from actual measurements employing bistatic lidar and solar radiometer.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 469-503
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  • 12
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    Application of statistical inversion to ground-based microwave remote sensing of temperature and water vapor profiles (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: Surface-based observations of downwelling microwave thermal emission are related to temperature and humidity profiles via a standard integral equation of radiative transfer. Both in clear and in cloudy atmospheres, statistical inversion techniques are used to retrieve profiles from a data vector of brightness observations and surface meteorological constraints. For the clear case, accuracy predictions and profile retrievals are illustrated for: (1) single frequency angular scanned data; (2) multi-frequency angular scanned data; and (3) multi-frequency zenith data. For the last case predicted and achieved accuracies were compared in a recently conducted radiometric experiment. Retrievals of cloud contaminated radiometric data are elaborated.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 395-427
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  • 13
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    Comparison of linear inversion methods by examination of the duality between iterative and inverse matrix methods (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: Linear numerical inversion methods applied to atmospheric remote sounding generally can be categorized in two ways: (1) iterative, and (2) inverse matrix methods. However, these two categories are not unrelated; a duality exists between them. In other words, given an iterative scheme, a corresponding inverse matrix method exists, and conversely. This duality concept is developed for the more familiar linear methods. The iterative duals are compared with the classical linear iterative approaches and their differences analyzed. The importance of the initial profile in all methods is stressed. Calculations using simulated data are made to compare accuracies and to examine the dependence of the solution on the initial profile.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 325-360
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  • 14
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    Analytic model approach to the inversion of scattering data (1977)
    In:  CASI
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    Publication Date: 2006-05-22
    Description: An analytic model approach is applied to several simple atmospheric inversion problems. This method gives a sharp determination of aerosol size distribution parameters. It is shown that this analytic approach, together with ground level point sampling data measurements, can be used to infer information on the tropospheric ozone profile.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 297-324
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  • 15
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    Inversion of infrared limb emission measurements for temperature and trace gas concentrations (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: Limb emission measurements are characterized by sharp weighting functions at high altitudes, and for temperature determinations, strongly nonlinear dependence of the weighting function on the temperature. Several methods for inverting this type of measurement have been described and used, including iterative, statistical, nonlinear and approximate direct approaches. These approaches are described and advantages and disadvantages of each are outlined.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 195-216
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  • 16
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    Inverse solution of the pseudoscalar transfer equation through nonlinear matrix inversion (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: Nonlinear matrix inversion operators have been developed which, applied to observed radiances, infer maximal information regarding atmospheric scattering parameters and vertical distribution of radiant sources and sinks. The algorithm has the attractive feature of noise discrimination, attributing instrumental errors to extra-atmospheric sources.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 139-153
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  • 17
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    Backus-Gilbert theory and its application to retrieval of ozone and temperature profiles (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: The inversion method provides a quantitative evaluation of the trade-off between vertical resolution of a retrieved profile and formal root-mean-square (rms) error due to measurement noise propagation. The problem of retrieving the top-side ozone profile from backscattered ultraviolet (BUV) measurements is considered. For measurements of the type currently being obtained with the Nimbus 4 and AE-E BUV experiments, it is found that a vertical resolution of approximately 0.75 scale height can be achieved for a formal volume mixing ratio profile error of 10%. Other examples include treatments of the retrieval of temperature profiles from measurements in the 15 micron CO2 absorption band for both the terrestrial and Martian atmospheres. Finally, the method is applied to the problem of retrieving temperature profiles of the Jovian planets from measurements in the far infrared pressure induced H2 lines to be obtained from the Mariner Jupiter/Saturn fly-by missions.
    Keywords: GEOPHYSICS
    Type: Inversion Methods in Atmospheric Remote Sounding; p 155-193
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  • 18
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    Statistical principles of inversion theory (1977)
    In:  CASI
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    Publication Date: 2006-05-22
    Description: Statistical methods are used to deal with the inverse problem of radiative transfer. All the available information about an unknown profile can be expressed in the form of values of functions of that profile and error estimates of these values. Estimation theory shows how these values are combined to give an estimate of the unknown profile and its error covariance. Many inversion methods are expressed in this form, although the error estimate is not usually carried out. Practical applications are described, both for inversion of individual profiles, and the global analysis of satellite data.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 117-138
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  • 19
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    Some aspects of the inversion problem in remote sensing (1977)
    In:  CASI
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    Publication Date: 2006-05-22
    Description: Several commonly used methods for inversion--constrained linear inversion, synthesis (Backus-Gilbert) methods and nonlinear iterative techniques for the Chahine type--are discussed. It is demonstrated that a very close connection exists between Backus-Gilbert solutions and those given by constrained linear inversion. A number of examples of the application of such methods are presented, showing that resolution is not greatly different for quite different algorithms, a result quite in accord with general theoretical considerations: more resolution can be achieved at the expense of introducing greater a priori bias in the procedure.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 41-65
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  • 20
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    Review of radiative transfer methods in scattering atmospheres (1977)
    In:  CASI
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    Publication Date: 2006-05-22
    Description: The radiative transfer in a scattering plane-parallel atmosphere is discussed, considering the exact analytical, the computational and the approximate methods. Some results of numerical comparisons are given. Finally, the difficulties of realistic atmospheric models are emphasized.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 21-40
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  • 21
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    Hybrid methods are helpful (1977)
    In:  CASI
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    Publication Date: 2006-05-22
    Description: Multiple scattering problems in a plane layer often permit the convenient use of different methods joined together. Sample numerical results to illustrate this point refer to X- and Y-functions, asymptotic fitting, the small-loss approximations, polarization in high orders, and photon path distribution.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Inversion Methods in Atmospheric Remote Sounding; p 1-19
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  • 22
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    National geodetic satellite program, part 1 (1977)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Determinations of tracking station locations and the gravitational constant of the earth, based on Doppler-tracking data from lunar and planetary spacecraft are presented. Two-way Doppler data obtained by the Deep Space Network of the Jet Propulsion Laboratory (JPL) were used. The Deep Space Station instrumentation that JPL employed is described. How the stations were located is detailed, and the data used are discussed. Results are given together with an analysis of the errors.
    Keywords: GEOPHYSICS
    Type: Natl. Geodetic Satellite Program, Pt. 1; p 249-292
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  • 23
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    National geodetic satellite program, part 1 (1977)
    In:  CASI
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    Publication Date: 2006-01-16
    Description: The Applied Physics Laboratory (APL) space research program was directed toward modeling the gravitational field of the earth from an analysis of the Doppler shifts on the transmitted frequencies of the satellites as obtained by the tracking stations. Emphasis is on the satellites involved and the methods used in accomplishing this aim.
    Keywords: GEOPHYSICS
    Type: NASA, Washington Natl. Geodetic Satellite Program, Pt. 1; p 89-138
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  • 24
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    Introduction: National geodetic satellite program, part 1 (1977)
    In:  CASI
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    Publication Date: 2006-01-16
    Description: Background for the National Geodetic Satellite Program (NGSP) is presented. An historical summary of the program and its technical structure is given. The technical structure of the program is described in enough detail that the reader can relate the work of the individual contributors to each other and to the NGSP.
    Keywords: GEOPHYSICS
    Type: NASA, Washington Natl. Geodetic Satellite Program, Pt. 1; p 3-85
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  • 25
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    National geodetic satellite program, part 1 (1977)
    In:  CASI
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    Publication Date: 2006-01-16
    Description: The major accomplishments of the GEOS-B, C-band systems project is assessed. The project objectives are given, namely: (1) primary objectives that must be met for project success; (2) secondary objectives that were sufficiently important to warrant serious consideration; and (3) other objectives that were important to the project and for which additional effort would be desirable. The primary objectives are presented and discussed in detail.
    Keywords: GEOPHYSICS
    Type: Natl. Geodetic Satellite Program, Pt. 1; p 487-524
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  • 26
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    National geodetic satellite program, part 1 (1977)
    In:  CASI
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    Publication Date: 2006-01-16
    Description: Equipment and techniques were evaluated operationally, by the Department of Defense, during the National Geodetic Satellite Program (NGSP). The theory, instrumentation, and data reduction methods used are described. Results obtained during the NGSP are given.
    Keywords: GEOPHYSICS
    Type: NASA, Washington Natl. Geodetic Satellite Program, Pt. 1; p 139-245
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  • 27
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    Stimulated plasma waves in the ionosphere (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The reported discussion is concerned with longitudinal waves associated with electron motions. These waves are easily stimulated in the ionosphere by rocket- and satellite-borne RF sounders. Most of the observations of stimulated plasma waves in the ionosphere are based on ionograms obtained from the sounders carried on board five satellites, including Explorer 20, Alouette 1 and 2, and ISIS 1 and 2. The majority of the observations can be explained by considering the propagation of the sounder-stimulated plasma waves. Attention is given to aspects of plasma wave dispersion, linear phenomena, plasma wave instabilities and nonlinear phenomena, unexplained phenomena, diagnostic applications, geophysical and astrophysical applications, and a number of experiments planned for the future.
    Keywords: GEOPHYSICS
    Type: Radio Science; 12; Nov
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  • 28
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    Primeval gas clouds and the low-energy X-ray background (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A model for the appearance of the all-sky low-energy X-ray background on a fine angular scale is presented which is based on primeval hot gas clouds associated with the formation of clusters of galaxies according to the Sunyaev-Zel'dovich (1972) model. It is noted that the background could have both granular and diffuse components if it is due to such gas clouds. The observed appearance of the granular component is predicted along with the observable characteristics of collapsing protoclusters. The effects of distant X-ray-emitting QSOs, radio galaxies, and normal galaxies on the observations are considered, and these sources are shown not to interfere with the possibility of observing the protoclusters. It is concluded that if sufficient heating occurred in an intracluster medium within some clusters of galaxies at the protocluster epoch, the ensemble properties of protoclusters could be observed with an X-ray telescope, and the time at which protoclusters formed could perhaps be estimated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 218
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  • 29
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    2.8 and 6 cm wavelength observations of NGC 7822 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 61; 2, Oc; Oct. 197
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  • 30
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    V 701 Scorpii and its place among early contact binaries (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 61; 1, Oc; Oct. 197
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  • 31
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    Structure of radio sources with remarkably flat spectra - PKS 0735+178 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Three incoherent synchrotron models are used to account for the very flat radio spectrum of the BL Lac object PKS 0735+178. The first interpretation is that the spectrum results from optically-thin synchrotron emission from relativistic electrons with a particular energy distribution. The second posits a single nonuniform, self-absorbed source generated by a wind flowing from a central object. The third suggests that sources with flat spectra are caused by the presence of multiple (three or more) discrete uniform components, and that the magnetic field and relativistic electron distribution for each source is correlated with the size of the individual components. It is proposed that the last model is the most tenable explanation of the phenomenon, and multi-frequency VLBI observations are suggested for the evaluation of the detailed structure of compact radio sources.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 82; Oct. 197
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  • 32
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    Search for microarcsecond structure in low-frequency variable radio sources (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A search for interstellar scintillation (ISS) of low-frequency variable radio sources is reported. Observations of 28 confirmed or suspected low-frequency variables, 21 nonvariable sources, and two pulsars were made at 408 MHz. As expected, the pulsars showed ISS, but scintillation was not detected in any other source. A typical upper limit to the rms modulation due to ISS is 150 mJy, giving lower limits to the apparent angular diameter of about 10 to the -6th arcsec. The possibilities that a true point source is broadened to an apparent angular diameter greater than or roughly equal to 10 to the -6th arcsec by scattering local to the source or in a general intergalactic medium are discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 82; Oct. 197
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  • 33
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    Extragalactic sources with strong millimeter-wave emission (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations at 90 GHz of a sample of 38 sources chosen to have flat or rising spectra between 0.318 and 5 GHz are reported. Roughly 25% of the sources were found to have flat or rising spectra between 5 and 90 GHz. The optical magnitude of each of the sources from the E print of the Palomar Sky Survey has also been estimated. Evidence is found for a correlation between the 90-GHz flux density and the optical magnitude, suggesting a relationship between the emission processes at these frequencies. Little evidence is found for a correlation between the low- and high-frequency spectral indices of the sources. This suggests that the sources tend to be opaque at centimeter wavelengths and optically thin at millimeter wavelengths. The properties of two of the more interesting sources are also discussed. Evidence is presented that strong millimeter activity may be generally associated with the BL Lac phenomenon.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 82; Oct. 197
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  • 34
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    Rare earth and trace element geochemistry of a fragment of Jurassic seafloor, Point Sal, California (1977)
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    Publication Date: 2011-08-17
    Description: Rocks from an ophiolite suite once on the seafloor were analyzed for rare earth elements (REE), Sc, Co, Na2O, Cr, Zn and FeO. Strontium isotope exchange noted in some of the lavas is attributed to basalt-seawater interaction; the Ce abundance in smectite- and zeolite-bearing lavas may also be due to prolonged exposure to seawater. The higher grades of metamorphic rock, however, show no variation from the usual flat or slightly light REE depleted profiles. Plutonic igneous rock, all light REE depleted, have total REE abundances varying by a factor of 100 between the dunites and diorites. In order of decreasing REE abundance are hornblende, clinopyroxene, plagioclase, orthopyroxene and olivine. Calculations of REE contents of liquids in equilibrium with early cumulative clinopyroxenes suggest that the parent to the stratiform sequence was more depleted in light REE than the parent to the lava pile.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta; 41; Oct. 197
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    Computer simulation of earthquakes (1977)
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    Publication Date: 2011-08-17
    Description: In a computer simulation study of earthquakes a seismically active strike slip fault is represented by coupled mechanical blocks which are driven by a moving plate and which slide on a friction surface. Elastic forces and time independent friction are used to generate main shock events, while viscoelastic forces and time dependent friction add aftershock features. The study reveals that the size, length, and time and place of event occurrence are strongly influenced by the magnitude and degree of homogeneity in the elastic, viscous, and friction parameters of the fault region. For example, periodically reoccurring similar events are observed in simulations with near-homogeneous parameters along the fault, whereas seismic gaps are a common feature of simulations employing large variations in the fault parameters. The study also reveals correlations between strain energy release and fault length and average displacement and between main shock and aftershock displacements.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Sept. 10
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    Supernovae, grains and the formation of the solar system (1977)
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    Publication Date: 2011-08-17
    Description: An investigation is conducted concerning the possibility that observed Mg-26 anomalies in meteorites may be related to a nucleosynthetic event which preceded the formation of the solar system by at most a few million years. The Al-26, which decayed to form the observed excess Mg-26, could have been produced in either explosive carbon burning or in a high temperature carbon burning shell source immediately preceding the explosion. The results of supernova grain condensation calculations are presented and related to the hypothesis that a 'last event' supernova was indeed related to the formation of the solar system and thus might have created the observed isotopic anomalies in magnesium, oxygen, neon, and xenon.
    Keywords: ASTROPHYSICS
    Type: Nature; 269; Sept. 8
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  • 37
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    The 1976 Standard Atmosphere and its relationship to earlier standards (1977)
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    Publication Date: 2011-08-17
    Description: The 1976 U.S. Standard Atmosphere, representing a mid-latitude atmosphere for moderate solar activity, is compared to earlier standards. For heights of 51 km and below, this standard is identical with its immediate predecessor, the 1962 U.S. Standard Atmosphere. When the density-height profile of each of five earlier model atmospheres is compared with that of the 1976 standard, an oscillation of this parameter around the currently accepted average value is observed, which is partly the result of true density changes related to the 11-year cycle of solar activity and partly the result of earlier uncertainties. The development of knowledge is also elucidated by comparing the temperature-height profiles of each of the important standards used during the preceding century. Number densities of each of six atmospheric species computed for the 1976 U.S. standard are compared over the height region of 0 to 1000 km.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 15; Aug. 197
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  • 38
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    A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS. I - N2 density and temperature (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Measurements of neutral nitrogen density from mass spectrometers on five satellites (AE-B, Ogo 6, San Marco 3, Aeros A, and AE-C) and neutral temperatures inferred from incoherent scatter measurements at four ground stations are combined to produce a model of thermospheric neutral temperatures and nitrogen densities similar to the Ogo 6 empirical model (Hedin et al., 1974). This global model is designated MSIS (mass spectrometer and incoherent scatter). The global average temperature, the annual temperature variation, lower bound density, and lower bound temperature are discussed. The data set covers the time period from the end of 1965 to mid-1975 and also a wide range of solar activities. Diurnal and semidiurnal variations in lower bound density and temperature are considered, as is magnetic activity.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; June 1
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  • 39
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    Lowest-order average effect of turbulence on atmospheric profiles derived from radio occultation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Turbulence in planetary atmospheres and ionospheres causes changes in angles of refraction of radio waves used in occultation experiments. Atmospheric temperature and pressure profiles, and ionospheric electron concentration profiles, derived from radio occultation measurements of Doppler frequency contain errors due to such angular offsets. The lowest-order average errors are derived from a geometrical-optics treatment of the radio-wave phase advance caused by the addition of uniform turbulence to an initially homogeneous medium. It is concluded that the average profile errors are small and that precise Doppler frequency measurements at two or more wavelengths could be used to help determine characteristics of the turbulence, as well as accuracy limits and possible correction terms for the profiles. However, a more detailed study of both frequency and intensity characteristics in radio and optical occultation measurements of turbulent planetary atmospheres and ionospheres is required to realize the full potential of such measurements.
    Keywords: GEOPHYSICS
    Type: Astrophysical Journal; vol. 214
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  • 40
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    The composition of comets (1977)
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    Publication Date: 2011-08-17
    Description: Questions concerning the origin of comets are considered. It is pointed out that the molecular composition of a dense interstellar cloud appears to have exactly the composition needed to produce the observed features of the visible cometary spectrum, which consists mainly of emission bands of unstable free radicals. A working model of cometary structure is discussed together with the classical observations which have led to it. The discussed model was originally described by Whipple (1951). It is emphasized that the model can serve only as a rough guide in efforts to interpret the evolution of cometary behavior. A survey is provided of new techniques which have only recently been applied to cometary observations, taking into account the spectrum of a comet, radio observations, and ultraviolet observations.
    Keywords: ASTROPHYSICS
    Type: American Scientist; 65; May-June
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  • 41
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    Nonradial pulsational instability of massive stars (1977)
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    Publication Date: 2011-08-17
    Description: Pulsational eigenfrequencies and stability coefficients of the lowest modes of nonradial quadrupole (l = 2) oscillation have been obtained for chemically homogeneous stellar models constructed with Carson's (1976) radiative opacities. Instability is found to develop as a result of the same operation of the kappa-mechanism in the CNO ionization zone and at nearly the same stellar masses as was the case for the radial (l = 0) modes studied previously. A survey of the l = 5 modes indicates that the instability gradually declines with increasing degree of the spherical harmonics.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 214
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  • 42
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    Observations of the mid-latitude lower ionosphere in winter (1977)
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    Publication Date: 2011-08-17
    Description: Rocket observations of the lower ionosphere in the winter of 1971 at two locations show differences of electron density which are attributed to enhancements of nitric oxide and energetic electron fluxes precipitated into the mesosphere during the poststorm phase of a geomagnetic storm. Electron density distributions were observed above Wallops Island, Virginia, and Keweenaw, Michigan, larger values occurring at Keweenaw. Energetic electron fluxes were greater at Keweenaw (L = 3.9) than at Wallops Island (L = 2.5). While particle ionization was the dominant factor in establishing the electron density during one measurement at Keweenaw, particles were not present two days earlier, even though the electron density distribution was significantly larger than that observed at Wallops Island on both occasions. An accompanying ion composition profile measured at Keweenaw during the earlier flight showed NO(+) to be the dominant ion to 76 km, where the concentration of hydrated ions H3O(+).(H2O)n, exceeded that of NO(+).
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; May 1
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  • 43
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    Large-scale electric fields in the earth's magnetosphere (1977)
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    Publication Date: 2011-08-17
    Description: Studies of the earth's magnetosphere have indicated that a large-scale electric field E plays a central role in its electrodynamics and in the flow and acceleration of charged particles there; while many observations relevant to E have accumulated, quite a few basic problems involving the origin and structure of this field remain unsolved. The ultimate source of E is presumably the flow of the solar wind past the earth, but the mechanism by which E arises is still unclear, and several independent sources may contribute to it, some of them being of a rather transient nature. This review attempts to sum up the main observed facts and theoretical concepts related to E.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 15; May 1977
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  • 44
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    Theoretical aspects of tidal and planetary wave propagation at thermospheric heights (1977)
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    Publication Date: 2011-08-17
    Description: A simple semiquantitative model is presented which allows analytic solutions of tidal and planetary wave propagation at thermospheric heights. This model is based on perturbation approximation and mode separation. The effects of viscosity and heat conduction are parameterized by Rayleigh friction and Newtonian cooling. Because of this simplicity, one gains a clear physical insight into basic features of atmospheric wave propagation. In particular, we discuss the meridional structures of pressure and horizontal wind (the solutions of Laplace's equation) and their modification due to dissipative effects at thermospheric heights. Furthermore, we solve the equations governing the height structure of the wave modes and arrive at a very simple asymptotic solution valid in the upper part of the thermosphere. That 'system transfer function' of the thermosphere allows one to estimate immediately the reaction of the thermospheric wave mode parameters such as pressure, temperature, and winds to an external heat source of arbitrary temporal and spatial distribution. Finally, the diffusion effects of the minor constituents due to the global wind circulation are discussed, and some results of numerical calculations are presented.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 15; May 1977
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  • 45
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    Variational electric fields at low latitudes and their relation to spread-F and plasma irregularities (1977)
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    Publication Date: 2011-08-17
    Description: In situ measurements of variational electric fields at low latitudes, taken by OGO 6 satellite instruments, are analyzed. The observations are compared with other data on F region and spread-F structures. Conformity of the electric field fluctuations with the overall picture of low-latitude irregularities is examined empirically and theoretically, and candidate processes for generation of the observed irregularities are considered. Three distinct types of irregularities are delineated and compared.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Mar. 197
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  • 46
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    The N.A.S.A. earth and ocean dynamics programme (1977)
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    Publication Date: 2011-08-17
    Description: Practical applications of NASA space systems, science, and technology to the study of oceans and solid earth are discussed. Goals involving earth dynamics include earthquake hazard assessment and alleviation, and global surveying and mapping, while goals involving ocean dynamics include the determination of ocean currents and circulation, and the monitoring of ocean surface conditions. Satellites used to obtain data are described, and projects such as the study of open ocean tides and earth motion determination are reviewed, with consideration given to the techniques (e.g., laser ranging, satellite-to-satellite track) used in these studies. Several physical phenomena, the extent to which they presently can be measured, and possible future requirements for more accurate measurements are examined.
    Keywords: GEOPHYSICS
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    Polar motion and earth tides from laser tracking (1977)
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    Publication Date: 2011-08-17
    Description: The paper discusses techniques available for measuring polar motion, earth rotation and earth tides with laser tracking of satellites. In a discussion of future prospects, it is noted that when the Laser Geodynamics Satellite is launched, a network of laser stations is projected to be able to achieve better than 10 cm from each coordinate from less than one day of tracking.
    Keywords: GEOPHYSICS
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  • 48
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    Probing the earth's gravity field by means of satellite-to-satellite tracking (1977)
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    Publication Date: 2011-08-17
    Description: Two satellite-to-satellite tracking (sst) tests are described in detail: (1) the ATS-6/Geos-3 and (2) the ATS-6/Apollo-Soyuz experiment. The main purpose of these two experiments was to track via ATS-6 the Geos-3, as well as the Apollo-Soyuz and to use these tracking data to determine both of the orbits at the same time, each of the orbits alone, and to test the two sst links to study local gravity anomalies. A second purpose was to test communications, command and data transmission from the ground via ATS-6 to these spacecraft and back again to the ground.
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  • 49
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    Pulsating aurora induced by upper atmospheric barium releases (1977)
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    Publication Date: 2011-08-17
    Description: The paper reports the apparent generation of pulsating aurora by explosive releases of barium vapor near 250 km altitude. This effect occurred only when the explosions were in the path of precipitating electrons associated with the visible aurora. Each explosive charge was a standard 1.5 kg thermite mixture of Ba and CuO with an excess of Ba metal which was vaporized and dispersed by the thermite explosion. Traces of Sr, Na, and Li were added to some of the charges, and monitoring was achieved by ground-based spectrophotometric observations. On March 28, 1976, an increase in emission at 5577 A and at 4278 A was observed in association with the first two bursts, these emissions pulsating with roughly a 10 sec period for approximately 60 to 100 sec after the burst.
    Keywords: GEOPHYSICS
    Type: Nature; 267; May 12
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  • 50
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    Galactic distribution of X-ray burst sources (1977)
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    Publication Date: 2011-08-17
    Description: Data on X-ray bursts recorded by the OSO-8 and SAS-3 satellites and criteria (rise time, duration, recurrence) for X-ray bursts are examined in a study of possible correlation between the galactic longitude distribution of X-ray burst sources and globular clusters. Correlations are weak, with only two X-ray bursts sources (NGC6624 and the rapid burster) coinciding with globular clusters, another seven possibly coinciding, most not correlated. Ad hoc explanations (globular clusters obscured by dust clouds, bursts associated with remnants of disrupted globular clusters evolved into supermassive black holes) are considered briefly.
    Keywords: ASTROPHYSICS
    Type: Nature; 267; May 5
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  • 51
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    The continuous UV flux of Alpha Lyrae - Non-LTE results (1977)
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    Publication Date: 2011-08-17
    Description: Non-LTE calculations for the ultraviolet C I and Si I continuous opacity show that LTE results overestimate the importance of these sources of opacity and underestimate the emergent flux in Alpha Lyr. The largest errors occur between 1100 and 1160 A, where the predicted flux in non-LTE is as much as 50 times larger than in LTE, in reasonable accord with Copernicus observations. The discrepancy between LTE models and observations has been interpreted to result from the existence of a chromosphere. Until a self-consistent non-LTE model atmosphere becomes available, such an interpretation is premature.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 214
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    Submillisecond measurements of the low state of Cygnus X-1 (1977)
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    Publication Date: 2011-08-17
    Description: Cygnus X-1 was observed on two occasions separated by a year by the same Goddard X-ray rocket payload. High-resolution temporal and spectral data reveal that Cyg X-1 was essentially unchanged in these two observations a year apart; the bursts of millisecond duration observed in the earlier flight were observed in the second as well. Analysis of these bursts has failed to reveal any internal temporal structure, either luminous or spectral. The shot-noise character of temporal fluctuations on time scales of at least 1 s can be explained by the presence of exponential pulses with a time constant of a fraction of a second and a rate near 8 per sec. The possible connection of these pulses with the bursts is examined.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 213
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    On the rapid variability of central stars of planetary nebulae (1977)
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    Publication Date: 2011-08-17
    Description: Envelope models for central stars of planetary nebulae have been constructed with Carson's (1976) radiative opacities. A stability analysis of these envelopes indicates that for a sufficiently high luminosity, the fundamental mode of radial pulsation is excited by the kappa mechanism operating in the CNO ionization zone. At somewhat higher luminosities the lowest overtones also become unstable. This may possibly explain the rapid variability that is observed in some central stars, if the time scale of the variations is minutes to hours.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 213
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  • 54
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    Accretion torques in X-ray pulsars (1977)
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    Publication Date: 2011-08-17
    Description: An analysis of the accretion process in an X-ray pulsar, whereby angular momentum is transferred to the star and its rotation period is changed, is presented, and an expression for the fractional rate of change of the pulse period in terms of X-ray luminosity and other star parameters is derived. It is shown that observed characteristic spin-up time scales for seven X-ray pulsars strongly support the view that in every source (1) the pulse period reflects the rotation period of a compact object, (2) the accretion is mediated by a disk surrounding the compact object and rotating in the same sense, and (3) the compact object is a neutron star rather than a white dwarf.
    Keywords: ASTROPHYSICS
    Type: Nature; 266; Apr. 21
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    Observation of neutral winds during an equatorial electrojet (1977)
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    Publication Date: 2011-08-17
    Description: The vertical profile of the horizontal wind in a strong equatorial electrojet is distinctly different from profiles observed previously at other times and locations. The zonal wind speed is small and varies slowly with altitude, whereas the meridional component manifests a cross-equatorial oscillation with altitude which may result from a unique interaction of the ionized and neutral motions.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Feb. 197
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    Observations of the unidentified 3.3 micron emission feature in nebulae (1977)
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    Publication Date: 2011-08-17
    Description: Spectrophotometric observations from 2.1 to 4.1 microns of a variety of objects exhibiting the 3.3-micron emission feature (first detected in NGC 7027) are reported. The characteristics of the feature, the various environments in which it is found, and possible emission mechanisms are discussed in light of all the available observations of the feature to date. A resonance feature in solids is the most probable emission mechanism; however, no satisfactory identification has yet been made on the basis of infrared spectroscopy of terrestrial materials.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 213
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    Spectrum of the Kleinmann-Low nebula from 29 to 125 micrometers (1977)
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    Publication Date: 2011-08-17
    Description: The infrared spectrum of the Kleinmann-Low nebula in M42 has been measured from 80 to 350 kaysers (approximately 29 to 125 microns) with a Michelson interferometer aboard the NASA Kuiper Airborne Observatory. The frequency spectrum peaks at about 185 kaysers. A simple model of the emission implies that the temperature is in the range 70-95 K and that the optical depth is at least 0.2 at the peak frequency. A possible absorption is seen at about 176 kaysers. Thermal emission by dust at a temperature of 71 K, with the absorption cross section proportional to frequency, provides a good fit to the data. Other thermal-emission models can also fit the spectrum. The data are compared with previous broad-band measurements. Upper limits are placed on expected line emission from the surrounding H II region at the position of the nebula.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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    The supernova trigger for formation of the solar system (1977)
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    Publication Date: 2011-08-17
    Description: It is suggested that the explosion of a Type II supernova triggered the collapse of a nearby interstellar cloud and led to the formation of the solar system. Estimates of the abundances resulting from nuclear processing of the supernova ejecta are presented. It appears promising that nucleosynthesis in this single supernova event can account for most isotopic anomalies and traces of extinct radioactivities in solar-system material.
    Keywords: ASTROPHYSICS
    Type: Icarus; 30; Mar. 197
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  • 59
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    Intercomparison of neutral composition measurements from the satellite Esro 4, Aeros A, Aeros B, and Atmosphere Explorer C (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Number-density data obtained at orbital 'crossover' points with the neutral-gas mass spectrometers aboard the Esro 4, Aeros A, AE-C, and Aeros B satellites are intercompared. All the mass spectrometers were designed to measure the ambient number densities of atomic oxygen, molecular nitrogen, helium, and argon. It is found that the agreement for N2 and O is satisfactory within the experimental errors and that the He measurements exhibit unexpectedly large discrepancies far outside the error range. Calibration and instrument sources of error are considered.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 60
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    Binary X-ray pulsars (1977)
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    Publication Date: 2011-08-17
    Description: Recent progress in the study of the pulse profiles of the nine known binary X-ray pulsars is discussed. The sources considered include SMC X-1, Her X-1, Cen X-3, A0535+26, GX1+4, 3U 0900-40, A1118-61, GX301-2, and 3U 0352+30. Sample X-ray profiles for these sources are provided, and general features exhibited by the profiles are identified. It is noted that the apparent existence of a gap in the period distribution of X-ray pulsars, in the range from about 5 to 100 sec, seems to be genuine within obvious statistical limitations and is probably not an observational effect. Two explanations for the production of X-ray pulsations are examined: one requiring a temporal modulation of mass accretion onto the surface of a neutron star and another requiring the funnelling of matter along magnetic field lines to the neutron star's surface.
    Keywords: ASTROPHYSICS
    Type: Nature; 266; Mar. 10
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  • 61
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    Laser-induced fluorescence of CN/X2 Sigma +/ produced by photolysis of C2N2 at 160 nm (1977)
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    Publication Date: 2011-08-17
    Description: The paper reports laser-induced fluorescence measurements of the initial product state distributions of CN(X2 Sigma +) produced during the photolysis of C2N2 at a wavelength of 160 nm. The parent molecules were photodissociated by an argon flash lamp, and saturated solutions of BBD in p-dioxane were used as a laser dye to produce radiation that excited CN radicals in the (upsilon-double-prime, N-prime) vibrational-rotational sublevels of the X state to the B-state sublevels. Spectral-line identification is discussed along with the observed rotational, electronic, and vibrational energy partitionings. The effect of added buffer gas (N2 or He) on the observed product state distributions is examined in order to monitor collisional energy transfer from CN(A2 Pi, upsilon = 0) to CN(X2 Sigma +, upsilon-double-prime = 4). It is found that both buffer gases produce population inversion between the upsilon-double-prime = 4 and upsilon-double-prime = 3 levels of the X state.
    Keywords: GEOPHYSICS
    Type: Journal of Chemical Physics; 66; Mar. 1
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    Spectrographic observations of comet West /1975 n/ (1977)
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    Publication Date: 2011-08-17
    Description: The spectrum of comet West (1975 n) was recorded on March 7 and 11, 1976, in the wavelength interval from 5700 to 8200 A at an intermediate resolution. One hundred twenty-two emission lines are reported, with 78 lines having identifications with spectral features of NH2, H2O(+), C2, O I forbidden emission, and Na I.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 89
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    Hydrostatic equilibrium of gas, extent of cosmic ray confinement, and radio emission in the Galaxy (1977)
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    Publication Date: 2011-08-17
    Description: A detailed study of the hydrostatic equilibrium of the gas-field system perpendicular to the galactic plane in the neighborhood of the sun, assuming that the magnetic field is parallel to the plane, has been carried out. It is found that the distribution of pressure due to cosmic rays and the magnetic field is different from that due to the gas. The observed radio spectrum in the direction of the galactic pole can be understood if one includes in the hydrostatic equilibrium the distribution of gas in the halo. The results of this analysis show that in the galactic plane, the cosmic-ray density is approximately 2 to 3 eV/cu cm with a magnetic-field strength of about 5 to 6 microgauss. It is inferred that cosmic rays are confined to a more extended volume in the Galaxy (with an equivalent thickness of at least 2 kpc in the solar neighborhood) than the gas disk, and the magnetic-field strength slowly decreases to a value of 1 microgauss only beyond about 5 kpc from the plane. Further, there is no evidence for a quasi-spherical radio halo, although the radio emission extends beyond the gas disk with scale height of at least 1 kpc. A lower limit of about 6 million years for the confinement of cosmic rays in the Galaxy has been set.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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    The black tide model of QSOs (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper develops certain aspects of a model wherein a QSO is a massive black hole located in a dense galactic nucleus, with its growth and luminosity fueled by tidal disruption of passing stars. Cross sections for tidal disruptions are calculated, taking into account the thermal energy of stars, relativistic effects, and partial disruption removing only the outer layers of a star. Accretion rates are computed for a realistic distribution of stellar masses and evolutionary phases, the effect of the black hole on the cluster distribution is examined, and the red-giant disruption rate is evaluated for hole mass of at least 300 million solar masses, the cutoff of disruption of main-sequence stars. The results show that this black-tide model can explain QSO luminosities of at least 1 trillion suns if the black hole remains almost maximally Kerr as it grows above 100 million solar masses and if 'loss-cone' depletion of the number of stars in disruptive orbits is unimportant.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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  • 65
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    Physics of magnetospheric substorms (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Magnetosphere substorm physics are updated in the monograph. Major topics include: (1) open magnetosphere and the auroral oval; (2) auroras and auroral particles; (3) plasma distribution in the magnetosphere; (4) magnetosphere responses to interplanetary disturbances; (5) magnetospheric substorms and magnetotail phenomena; (6) magnetospheric currents, plasma injection, plasmasphere disturbances; and (7) magnetospheric substorms and solar-terrestrial relations. Other topics covered include: open field lines and the open magnetosphere, field-aligned currents, auroral particles and atmospheric emissions, plasma mantle, plasma sheet, radiation belts, magnetic flux transfer to the magnetotail, polar cap phenomena, substorm parameters, thinning of the plasma sheet, auroral electrojets, diurnal variations and dawn-dusk asymmetry of particle distributions, and instabilities.
    Keywords: GEOPHYSICS
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  • 66
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    On high-latitude convection field inhomogeneities, parallel electric fields and inverted-V precipitation events (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A simple model of a static electric field with a component parallel to the magnetic field is proposed for calculating the electric field and current distributions at various altitudes when the horizontal distribution of the convection electric field is given at a certain altitude above the auroral ionosphere. The model is shown to be compatible with satellite observations of inverted-V electron precipitation structures and associated irregularities in the convection electric field.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 25; Jan. 197
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  • 67
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    The storm-time equatorial electrojet (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A Petrel rocket carrying a double cell rubidium magnetometer was launched from the Thumba Equatorial Rocket Launching Station during the early main phase of a magnetic storm. No ionospheric currents associated with the storm were observed, and the large field depression at the flight time must therefore be attributed to currents at higher altitudes. The equatorial enhancement of ionospheric magnetic storm currents, predicted on the basis of theory and earlier ground data, was not observed.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Jan. 197
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  • 68
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    The 5-day wave and ionospheric absorption (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In a previous paper, Fraser and Thorpe (1976) indicated that the average partial-coherence spectra for three summers and the average for three winters at a southern mid-latitude site had a dominant peak at a period of about six days. This peak in coherence between absorption and temperature is anomalous, and the present paper explains how some of the unexpected coherence features can be explained by the five-day wave described by Geisler and Dickinson (1976) and whose existence in the upper stratosphere was discussed by Rodgers (1976).
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Jan. 197
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  • 69
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    Isotopic abundance of CO in interstellar clouds (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The fractional abundances of the isotopic species of carbon monoxide in interstellar clouds are calculated on a basis of gas-phase ion-molecule reactions. The (C-13)O/(C-12)O ratio varies significantly with extinction of the ultraviolet radiation field, and in the outer regions of dark dense clouds (C-13)O may be enhanced by a factor of 10. The observational interpretation of the CO to H2 or interstellar-reddening relation and the isotopic abundances of carbon are complicated by these effects.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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  • 70
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    The hard X-ray pulse profile of the transient source A0535+26 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Measurements of the 104 sec pulse profile of A0535+26 at energies near 50 keV are reported. The data were obtained with a balloon-borne detector system which was launched on May 22, 1975 with the objective to observe transient or periodic emissions from X-ray or gamma-ray sources. The presence of the source was detected by a superposed epoch analysis. The pulse profile of A0535+26 in two energy channels is presented in a graph.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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  • 71
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    All-Sky Monitor observations of the decay of A0620-00 /Nova Monocerotis 1975/ (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The All-Sky X-ray Monitor on board Ariel-5 has observed the 3-6 keV decline of the bright transient X-ray source A0620-00 on a virtually continuous basis during the period 1975 September-1976 March. The source behavior on time scales greater than about 100 minutes is characterized by smooth, exponential decays interrupted by substantial increases in October and February. The latter increase was an order-of-magnitude rise above the extrapolated exponential falloff, and was followed by a final rapid decline below a level of about 0.05 per sq cm per sec by late March. Upper limits of 2.5% and 10% were found for any periodicities in the range 0.2-10 days during the early and later decay phases, respectively. A probable correlation between the optical and 3-6 keV emission from A0620-00 has been noted, effectively ruling out models involving traditional optical novae in favor of Roche-lobe overflow in a binary system. The existing data on the transient X-ray sources are consistent with two distinct luminosity-lifetime classes of these objects.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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  • 72
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    Orbital changes of the gaseous ring around Be stars (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In order to understand the seemingly erratic V/R variations and radial velocity curves of emission edges and central absorption of some Be stars, we have advanced, for the changes of structure of the gaseous ring around these stars, a theory that is based on the interaction between the existing ring and the newly ejected matter from the star. It shows that the structural change of the ring is completely controlled by the angular-momentum input factor and the dissipation factor. In light of this understanding, we have gone on to interpret the observed results of Beta-1 Mon and Pi Aqr.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 212
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  • 73
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    Geopotential resonances on Vanguard orbits (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Since their establishment in 1959 the orbits of Vanguard 3 (1959-7A) and the Vanguard 2 rocket (1959-2B) have been slowly contracting through at least five strong resonances of eleventh order. Tracking with Baker-Nunn cameras and the U.S. Navy space surveillance (radio interferometer) system over a 14-year period has revealed resonant fluctuations on them of up to 0.035 deg in inclination (peak to peak). Six geopotential terms (lumped coefficients) of eleventh order and three of twenty-second order have been measured by using orbit inclinations derived from this tracking record. The terms of eleventh order are significantly smaller than is predicted by Kaula's rule. (The lumped coefficients are sensitive to geopotential effects as high as thirty-seventh degree.) These observed terms are compatible with a recent 27-satellite geopotential solution (GEM 7) whose formal coefficent errors are increased by a factor of 3.3.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Feb. 10
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  • 74
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    Improvement in the geopotential derived from satellite and surface data /Gem 7 and 8/ (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A refinement has been obtained in the earth's gravitational field by using satellite and surface data. In addition to a more complete treatment of data previously employed on 27 satellites, the new satellite solution Gem 7 (Goddard Earth Model 7) includes 64,000 laser measurements taken on seven satellites. Gem 7, containing 400 harmonic terms, is complete through degree and order 16. The companion solution Gem 8 combines the same satellite data as Gem 7 with surface gravimetry over 39% of the earth. Gem 8 is complete to degree and order 25. Extensive tests on data independent of the solution show that the undulations of the geoidal surface computed by Gem 7 have an accuracy of about 2.5 m (rms). The overall accuracy of the geoid calculated by Gem 8 is estimated to be about 4 m (rms). The new combination solution is the first to show signs of 'convection rolls' in the upper mantle below the Pacific Ocean.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Feb. 10
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  • 75
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    Recurrent X-ray outbursts from Aquila X-1 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Ariel V All-Sky Monitor observations of Aql X-1 are reported and compared with previous observations that indicate the existence of 'low' and 'high' intensity states. All the data considered are shown to be consistent with flaring episodes having a mean flare interval of 435 days with an rms scatter of about 10%. It is suggested that the observations are most easily interpreted in terms of an 'X-ray dwarf nova' binary of the type proposed for the transient X-ray source A0620-00. Constraints on more detailed features of the source model are discussed.
    Keywords: ASTROPHYSICS
    Type: Nature; 265; Feb. 17
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  • 76
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    Solar wind plasma injection at the dayside magnetospheric cusp (1977)
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    Publication Date: 2011-08-17
    Description: Two mechanisms have been proposed for solar wind particle injection at the dayside magnetospheric cusps: magnetic merging and cross-field diffusion. These two mechanisms are experimentally distinguishable in that they produce different latitudinal distributions of particles penetrating to the low-altitude cusp. An examination of proton and electron measurements obtained by the AE-C satellite in the low-altitude dayside cusp reveals evidence of both types of injection processes. A majority of the injection events, especially the more intense fluxes, are best explained by a merging injection model in which cusp particles are confined to the poleward side of the last closed field line and have a characteristic energy that decreases with increasing latitudinal distance from the last closed field line. Less frequent and less intense injection events are better explained in terms of a diffusive injection of cusp particles onto closed dayside field lines with a characteristic energy that increases with increasing latitudinal distance from the last closed field line. Although diffusion appears to be quantitatively less important than merging in terms of the instantaneous particle injection rate, cross-field diffusion nevertheless appears to proceed at an unexpectedly fast rate, possibly exceeding the Bohm diffusion limit.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Feb. 1
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  • 77
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    On the relationship of interstellar N2H/+/, HCO/+/, HCN, and CN (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A survey of 73 sources has been made in the emission lines of N2H(+) and HCO(+), including detailed maps of four sources (Ori A, OMC-2, DR 21 OH, and NGC 6334). These data are combined with equally extensive data for HCN and CN to make a detailed study of the spatial relationship of these four species. Actual abundance ratios are shown to vary, often sharply, over small scale lengths (of the order of 1 arcmin) within the mapped sources. Excitation temperatures also vary. All four species appear to be subthermally excited. The abundance ratios and their spatial variations are interpreted in terms of ion-molecular formation and destruction processes. It is concluded that the relative abundances of CO may be considerably lower in some regions than previously believed. No evidence is found for variations in the C/O ratio over small scale lengths in Ori A. The degree of ionization of the Ori A molecular cloud may be significantly different from that of other molecular clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 211
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  • 78
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    Variations in eddy diffusion and associated transport processes (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Variation in the eddy diffusion coefficient constitutes a momentum source. This variation near the turbopause affects both the composition and the wind and temperature fields of the thermosphere. Two types of calculations are carried out, for horizontal winds considered self-consistently in a three-dimensional dynamic model and horizontal winds artificially suppressed to simulate a one-dimensional model. Momentum transfer associated with variations in eddy diffusion coefficients represents the source function in the analysis presented. It is shown that for long-term variations in the thermosphere, the compositional dependence on variations in eddy diffusion coefficients can be entirely different in one and three dimensional models with horizontal winds included. Horizontal winds can greatly reduce the effects of eddy diffusion in general and the ratio between He and O amplitudes in particular.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 4; Jan. 197
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  • 79
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    A simple physical model for X-ray burst sources (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In connection with information considered by Illarianov and Sunyaev (1975) and van den Heuvel (1975), a simple physical model for an X-ray burst source in the galactic disk is proposed. The model includes an unevolved OB star with a relatively weak stellar wind and a compact object in a close binary system. For some reason, the stellar wind from the OB star is unable to accrete steadily on to the compact object. When the stellar wind is sufficiently weak, the compact object accretes irregularly, leading to X-ray bursts.
    Keywords: ASTROPHYSICS
    Type: Nature; 265; Jan. 20
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  • 80
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    Optical constants of ammonium sulfate in the infrared (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The infrared spectral reflectance at near normal incidence has been measured for 3.2 M, 2.4 M, and 1.6 M solutions of ammonium sulfate, an aerosol abundant in the stratosphere and also present in the troposphere. Kramers-Kronig analysis was used to determine values of the refractive and absorption indices from the measured spectral reflectance. A synthetic spectrum of crystalline ammonium sulfate was obtained by extrapolation of the absorption index obtained for the solution to the absorber number densities of the NH4 and SO4 ions characteristic of the crystal.
    Keywords: GEOPHYSICS
    Type: Optical Society of America; vol. 67
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  • 81
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    Simultaneous in situ magnetospheric and ionospheric detection of detached plasmas (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: On January 19, 1972, in situ measurements by Explorer 45, orbiting in the magnetosphere near the equatorial plane, and ISIS 2, in a circular polar orbit at 1400 km, simultaneously detected patches of enhanced ionization outside the main body of the plasmasphere. The magnetospheric plasma region extended between (geomagnetic latitude) L values 3.4-4.8 and the ionospheric electron density enhancement extended between L values 3.6-4.4. The two plasma features were detected near 22 hours magnetic local time (MLT). Based on a number of observations, it is inferred that the plasma density enhancement persisted for more than 5 hours and extended over at least 2 hours in MLT near L = 5. These results provide experimental evidence that some detached magnetospheric plasma regions are signatures of a flux tube containing enhanced ionization throughout a volume extending from the topside ionosphere out to the equator.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 4; Sept
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  • 82
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    Electric and magnetic fields in the high-latitude magnetosphere (1977)
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    Publication Date: 2011-08-17
    Description: The configuration of high-latitude electric and magnetic fields is reviewed. Various results suggest that high-latitude magnetic field lines from the outermost regions of the dayside magnetosphere converge toward a point near the noon meridian. Plasma flows, the midday cusp, and a dawn-dusk electric field across the polar cap are characterized. The electric fields associated with plasma flows produce Hall currents on the polar cap which vary with sector structure. Some evidence indicates that polar cap convection may reverse during intervals of strong northward interplanetary field. It is concluded that most observations are consistent with an open field magnetosphere model.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 15; Aug. 197
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  • 83
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    Reduction and treatment of magnetic anomalies of crustal origin in satellite data (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The problem of proper reduction and treatment of the residual total magnetic field observed on satellite orbits is studied. The reduction procedure used for Pogo satellite data is reviewed, and a procedure is presented for reducing the residual total field observed on satellite orbits to a spherical surface. Several examples based on selected models are provided to demonstrate the accuracy of the formulas developed for continuation of the satellite data from an irregular to a spherical surface. This procedure is tested on a set of Pogo data covering the area that contains the Bangui magnetic anomaly in central Africa. A technique is also given for determining the field components on a spherical surface and calculating the total field in any fixed direction of the geomagnetic field.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Aug. 10
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    Terrestrial kilometric radiation. III - Average spectral properties (1977)
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    Publication Date: 2011-08-17
    Description: The spectral properties of terrestrial kilometric radiation (TKR) derived from observations made during radio-astronomy experiments on board the Imp 6 and Radio Astronomy Explorer 2 spacecraft are studied. As viewed from near the equatorial plane, TKR is most intense and most often observed in the 2100-2400 LT zone and is rarely seen in the 0900-1200 LT zone. The absolute flux levels in the 100- to 600-kHz TKR band increase significantly with increasing substorm activity as inferred from the auroral electrojet index (AE). In the late-evening sector the median power increases by about 3 orders of magnitude between quiet periods (AE less than 75 gammas) and disturbed periods (AE above 200 gammas). The peak flux density usually occurs near 250 kHz, although the frequency of the peak in the flux spectrum appears to vary inversely with AE from a maximum near 300 kHz during very quiet times to a minimum below 200 kHz during very disturbed times. The half-power bandwidth is typically 100% of the peak frequency. The variation of TKR flux density with apparent source altitude indicates that source strength decreases more rapidly than the inverse square of distance.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Aug. 1
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  • 85
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    Interplanetary current sheets at 1 AU (1977)
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    Publication Date: 2011-08-17
    Description: The structure and nature of 'discontinuities' in the interplanetary magnetic field at 1 AU in the period from March 18 to April 9, 1971, is determined by using high-resolution magnetic-field measurements from Explorer 43. The discontinuities that were selected for this analysis occurred under a variety of interplanetary conditions at an average rate of 0.5/hour. Both tangential and rotational discontinuities were identified. Tangential discontinuities were observed every day, even among Alfvenic fluctuations. In particular, on one day during which Alfvenic fluctuations were intense and persistent in a high-speed stream, tangential discontinuities (TD's) were seen throughout the day at an average rate of 0.5/hour; rotational discontinuities (RD's) were also observed during this day at a higher than usual rate, the ratio of TD's to RD's being approximately one. The structure of most of the current sheets was simple and ordered; i.e., the magnetic field usually changed smoothly and monotonically from one side of the current sheet to the other. The thickness distributions of the TD's and RD's with very smooth current sheets were similar. The average thickness of the RD's was 1200 km (13 proton Larmor radii), and the average thickness of the TD's was 1300 km (12 proton Larmor radii).
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 82; Aug. 1
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    Observations of neutral composition and related ionospheric variations during a magnetic storm in February 1974 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The neutral-atmosphere composition experiment on Atmosphere Explorer C measured N2, O, Ar, and He densities during a magnetic storm at altitudes down to about 160 km. At latitudes above 45 deg N, N2 and Ar densities generally increase during the storm, while He and O densities decrease. Below 45 deg N all densities tend to increase during the storm. The density increases at perigee indicate that density- or temperature-profile changes are taking place below 160 km. The return to prestorm conditions is very slow, demonstrating the integrating effect of the atmospheric response. A recent theoretical model incorporating thermospheric circulation and diffusion effects reproduces the longitudinally averaged data, including latitude trends and the asymmetry about the storm maximum. Comparison with the mass-spectrometer and incoherent-scatter empirical model shows qualitative agreement with latitude trends but not with storm asymmetry, while the earlier J71 model based on total mass density is not in agreement with observed latitudinal trends. A close correlation is found between in situ O/N2 measurements and in situ and ground-based ionosonde measurements of electron density.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Aug. 1
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  • 87
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    Mass loss, long-period variables, and the formation of circumnebular shells (1977)
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    Publication Date: 2011-08-17
    Description: We have found that the rate of mass loss M increases with an increase in the period of pulsation for Mira-type variables. This result suggests that the rate of mass loss is accelerated with time until a maximum value is reached before the ejection of the outer envelope. The matter from the continuous mass loss during the evolution of the star produces supersonic shock waves that sweep up the interstellar gas upon encountering the interstellar medium, so that a shell is formed. This phenomenon may account for the observations of extended regions of emission that surround planetary nebulae.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 216
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  • 88
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    Evidence for mass loss in the mid-ultraviolet spectra of Be stars (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The spectral region about the Mg II doublet lines near 2800 A of Be and shell stars has been observed. The star Gamma Cas shows narrow components to each resonance doublet line shifted 215 km/s toward shorter wavelengths. The resonance and subordinate lines of Zeta Tau are shifted toward shorter wavelengths by 75 km/s, and the subordinate lines are greatly strengthened. The star Kappa Dra, which is much later in spectral type, shows a comparatively normal doublet spectrum.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 216
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  • 89
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    Scale-covariant theory of gravitation and astrophysical applications (1977)
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    Publication Date: 2011-08-17
    Description: Generalized Einstein equations invariant under scale transformations are presented, and several astrophysical tests studied. It is assumed that the dynamics of atoms or clocks used as measuring apparatus is given a priori. Connection with gauge fields and broken symmetries is made through the cosmological constant.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 39; Aug. 22
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  • 90
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    Solar proton event - Influence on stratospheric ozone (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Large-scale reductions in the ozone content of the middle and upper stratosphere over the polar cap regions were associated with the major solar proton event of 4 August 1972. This reduction, which was determined from measurements with the backscattered ultraviolet experiment on the Nimbus 4 satellite, is interpreted as being due to the catalytic destruction of ozone by odd-nitrogen compounds (NOx) produced by the event.
    Keywords: GEOPHYSICS
    Type: Science; 197; Aug. 26
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  • 91
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    What is a cometary nucleus (1977)
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    Publication Date: 2011-08-17
    Description: The meaning of the term 'cometary nucleus' is discussed, taking into account observations of comets with different characteristics. It is pointed out that for some comets, there may be no nucleus to be seen at any time, while in others as the comet brightens or undergoes changes, a nucleus may develop to be seen for a time or even intermittently, while occasionally more than one nucleus may be seen to be present. On the basis of a study of observational reports it emerges that no more than about 30 per cent of comets exhibit anything resembling a starlike nucleus.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 18
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  • 92
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    Statistical equilibrium in cometary C2. I (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Swan-band emission from the C2 molecule provides important information for a study of the physical processes occurring in comets. It is, therefore, a disturbing factor that many quantitative Swan-band observations are in clear contradiction of predictions of resonance fluorescence excitation of the Swan bands. A description is presented of an investigation involving an application of resonance fluorescence theory to C2. The investigation takes into account all important electronic transitions which determine the population distribution of the lowest energy states. It is found that the previous discrepancy for the brighter band sequences disappears.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 216
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  • 93
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    Evolution of helium stars (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The evolution of helium stars in the mass range from 4 to 15 solar masses has been followed from the initial helium main sequence to the end of carbon burning in the core, with the use of Carson's (1976) radiative opacities. As compared with earlier work based on smaller opacities, the main-sequence band in the H-R diagram is now both wider and cooler than before. If neutrino losses are neglected in the stellar models, the phase of carbon burning in the core occurs in the red-supergiant region; otherwise, it occurs, as it does in the earlier models with or without neutrino emission, close to the helium main sequence. Observational data for Wolf-Rayet stars and R Coronae Borealis variables are found to lend some support to the present models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 216
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  • 94
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    Optical, infrared and radio studies of compact H II regions. II - The H alpha knot S88B (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 59; 2, Ju; July 197
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  • 95
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    Model of climate evolution based on continental drift and polar wandering (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The thermodynamic meteorologic model of Adem is used to trace the evolution of climate from Triassic to present time by applying it to changing geography as described by continental drift and polar wandering. Results show that the gross changes of climate in the Northern Hemisphere can be fully explained by the strong cooling in high latitudes as continents moved poleward. High-latitude mean temperatures in the Northern Hemisphere dropped below the freezing point 10 to 15 m.y. ago, thereby accounting for the late Cenozoic glacial age. Computed meridional temperature gradients for the Northern Hemisphere steepened from 20 to 40 C over the 200-m.y. period, an effect caused primarily by the high-latitude temperature decrease. The primary result of the work is that the cooling that has occurred since the warm Mesozoic period and has culminated in glaciation is explainable wholly by terrestrial processes.
    Keywords: GEOPHYSICS
    Type: Geological Society of America; vol. 88
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  • 96
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    Lyman-alpha observations of Comet West /1975n/ (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The rate of hydrogen production of Comet West is studied through rocket observation of solar Lyman-alpha radiation resonantly scattered by the escaping hydrogen atoms. Two sets of Lyman-alpha exposure sequences are used to obtain computer-smoothed brightness contour (isophote) maps covering a density range of 100:1. A simple radial outflow model is applied to the contour maps to determine the rate of hydrogen production (3.2 by 10 to the 30th power atoms/sec.) Discrepancies between the observed shape of the outer isophotes and predicted models may be explained by optical depth effects, or by the presence of small pieces of the comet's nucleus distributed along the orbit. Hydrogen, carbon, and oxygen production for Comet West and Comet Kohoutek are compared; differences may be accounted for by variations in the composition or evolution of the two comets.
    Keywords: ASTROPHYSICS
    Type: Icarus; 31; Aug. 197
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  • 97
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    Interstellar clouds and molecular hydrogen (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Data obtained from the Copernicus Orbiting Astronomical Observatory, launched in 1972 and still obtaining information, are used in a discussion of the interstellar medium. The Copernicus instruments have facilitated direct estimates for the density and temperature of individual interstellar clouds, and improved the ability to determine where along the line of sight a cloud lies with respect to background stars. The physical characteristics of hydrogen molecules are considered, with attention to the formation and destruction of interstellar hydrogen. The differences between 'thin' clouds, in which molecular hydrogen is optically thin, and 'thick' clouds are examined. Several features of the interstellar medium are described.
    Keywords: ASTROPHYSICS
    Type: American Scientist; 65; July-Aug
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  • 98
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    Positions of X-ray sources near the galactic center measured by the Ariel-5 RMC experiment (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
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  • 99
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    Spectroscopic studies of very old hot stars. III - Atmospheric properties of seven planetary nuclei (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The atmospheric properties of seven planetary nuclei which have O or Of-type spectra were determined by use of the Zanstra method and by analysis of the visual line spectra. One finding is that the O-type spectral sequence may extend to effective temperatures of 90,000 kelvins or more, if the results of the Zanstra method are to be believed. However, there are some indications of internal inconsistency in the Zanstra method and some outstanding discrepancies between the effective temperatures indicated by the Zanstra method and those indicated from analysis of the visual line spectra. Two ways to resolve these discrepancies are to postulate an excess of extreme-UV stellar flux or to postulate a hot binary companion for some central stars. In either case the validity of the Harmon-Seaton evolutionary sequence for central stars becomes questionable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
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  • 100
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    The relationship between the galactic matter distribution, cosmic-ray dynamics, and gamma-ray production (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The concept that cosmic-ray density is related to the matter to which cosmic rays are dynamically coupled through magnetic fields on the scale of galactic arm segments is considered with specific reference to gamma-ray astronomy. A model of the galactic-matter and cosmic-ray distributions is developed on the basis of 21-cm radio surveys and recent observations of the 2.6-mm CO emission line by assuming that cosmic rays are galactic in origin, their column density is proportional to the total interstellar-gas column density, their scale height is considerably larger than that of the matter, and the Galaxy is a spiral with an arm/interarm density ratio of about 3 to 1. It is found that there is a good correlation between the observed gamma-ray intensity and that predicted on the basis of essentially complete coupling of cosmic rays to the best estimate of atomic and molecular hydrogen in the Galaxy. Individual maxima observed in gamma-radiation from the central region of the Galaxy are shown to be well correlated with those predicted to result from certain spiral-arm tangents if all the matter is assumed to be modulated in a particular spiral-arm segment pattern.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
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