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  • GEOPHYSICS  (914)
  • 2015-2019
  • 1995-1999
  • 1980-1984
  • 1975-1979  (914)
  • 1925-1929
  • 1999
  • 1978  (465)
  • 1976  (449)
Collection
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  • 2015-2019
  • 1995-1999
  • 1980-1984
  • 1975-1979  (914)
  • 1925-1929
Year
  • 1
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    Mathematical modelling of undrained clay behavior (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The proposed general analytical model describes the anisotropic, elastoplastic, path-dependent, stress-strain properties of inviscid saturated clays under undrained conditions. Model parameters are determined by using results from strain-controlled simple shear tests on a saturated clay. The model's accuracy is evaluated by applying it to predict the results of other tests on the same clay, including monotonic and cyclic loading. The model explains the very anisotropic shear strength behavior observed for weak marine clays.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 1; p 95-102
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  • 2
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    The Limb Infrared Monitor of the Stratosphere (LIMS) experiment (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Limb Infrared Monitor of the Stratosphere is used to obtain vertical profiles and maps of temperature and the concentration of ozone, water vapor, nitrogen dioxide, and nitric acid for the region of the stratosphere bounded by the upper troposphere and the lower mesosphere.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center The Nimbus 7 User's Guide; p 71-104
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  • 3
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    Microwave radiometer measurement of water vapor path delay: Data reduction techniques (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Data reduction techniques are developed to compensate for water vapor path delay, a limiting error source in geodetic measurements made with very long baseline interferometry and in radio ranging to spacecraft. It is shown that water vapor path delay is proportional to a linear combination of saturation-corrected sky brightness temperatures, measured on and off the water vapor line. The effects of emission from liquid water droplets in clouds as well as most of the oxygen emission are removed by the off-line channel. Sky brightness temperatures are saturation-corrected or 'linearized' using estimates of effective sky temperatures made from surface temperature. Tipping curves are used to remove instrumental error. Coefficients are found by two methods: from a regression analysis of measured brightness temperatures versus radiosonde measured delay, and from a regression analysis of theoretical brightness temperatures versus radiosonde measured delay. In each case the coefficients are adjusted for differing climatic conditions by measurements of surface temperature, pressure, and relative humidity. Regression solutions are constrained to remove liquid water contributions and to give the correct slope for radiometer versus radiosonde path delay.
    Keywords: GEOPHYSICS
    Type: The Deep Space Network; p 22-30
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  • 4
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    The Stratospheric and Mesospheric Sounder (SAMS) experiment (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Thermal emission and solar resonance fluorescence from the atmospheric limb are reported. Global measurements are made of radiation from the molecular species. The gas correlation spectroscopy technique based on the use of gas cells to select emission from chosen spectral lines or from particular parts of spectral lines is used. The source function and departure from the thermodynamic equilibrium between 80 and 130 kilometers associated with CO2 emission bands were investigated. The zonal wind velocity component along the line of sight is measured.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center The Nimbus 7 User's Guide; p 139-174
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  • 5
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    The Earth Radiation Budget (ERB) experiment (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The radiation budget of the earth on both synoptic and planetary scales by simultaneous measurement of incoming solar radiation and outgoing earth reflected (shortwave) and emitted (longwave) radiation was determined. Both fixed wide angle sampling of terrestrial fluxes at the satellite altitude, and scanned narrow-angle sampling of the radiance components, dependent on angle are used to determine outgoing radiation. Measurements of radiation are obtained in 22 different optical channels.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center The Nimbus 7 User's Guide; p 33-58
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  • 6
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    Geodynamics experiment MA-128 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Apollo Soyuz Test Project Geodynamics Experiment was performed to assess the feasibility of tracking and recovering high frequency components of the earth gravity field by utilizing a synchronous orbiting tracking station such as Applications Technology Satellite 6. Two prime areas of data collection were selected for this experiment. The first area is the center of the African continent, and the second area is the Indian Ocean depression centered at latitude 5 N and longitude 75 E. Preliminary results show that the detectability objective of the experiment has been achieved in both areas as well as in several additional anomalous areas around the globe. Gravity anomalies of the Karakoram and Himalayan mountain ranges of ocean trenches, and of the Diamantina depth are specific examples.
    Keywords: GEOPHYSICS
    Type: Apollo-Soyuz Test Project; 16 p
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  • 7
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    Stratospheric Aerosol Measurement (SAM 2) experiment (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Stratospheric Aerosol Measurement 2 (SAM 2) is used to map the concentration and optical properties of stratospheric aerosols as a function of altitude, latitude, and longitude. The vertical distribution of the stratospheric aerosols in the polar regions of both hemispheres is provided.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center The Nimbus 7 User's Guide; p 105-138
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  • 8
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    Doppler tracking experiment MA-089 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Doppler tracking experiment was designed to test the feasibility of improved mapping of earth gravity field anomalies by means of the low-low satellite-to-satellite tracking method. All prescribed data have been retrieved and are currently being reduced and analyzed. Baseline data taken while the docking module was still attached to the command and service module indicated that the equipment operated satisfactorily. The efficacy of the two frequency ionospheric correction method has been demonstrated, and preliminary reduction of a data sample has successfully removed extraneous signatures down to the 50-millihertz level, where the rotational motion of the docking module is revealed. Photographs of the docking module, taken shortly after jettison, show that its rotation was stable.
    Keywords: GEOPHYSICS
    Type: NASA. Lyndon B. Johnson Space Center Apollo-Soyuz Test Project; 31 p
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  • 9
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    Thermal structure of the primitive ionosphere (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Exospheric neutral and electron temperatures have been estimated for the primitive upper atmosphere and ionosphere with various oxygen content in the scheme of our previous model (Shimizu and Shimazaki, 1976). The exospheric neutral temperature has been shown to be rather insensitive to the change of oxygen content, justifying our previous assumption for the temperature variation, while the exospheric electron temperature has been found to be quite sensitive to the compositional change, mainly owing to the strong dependence of electron density on the oxygen concentration.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Jan. 1
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  • 10
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    The evolution of the atmosphere of the earth (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Computer simulations of the evolution of the earth's atmospheric composition and surface temperature have been carried out. The program took into account changes in the solar luminosity, variations in the earth's albedo, the greenhouse effect, variation in the biomass, and a variety of geochemical processes. Results indicate that prior to two billion years ago the earth had a partially reduced atmosphere, which included N2, CO2, reduced carbon compounds, some NH3, but no free H2. Surface temperatures were higher than now, due to a large greenhouse effect. When free O2 appeared the temperature fell sharply. Had earth been only slightly further from the sun, runaway glaciation would have occurred at that time. Simulations also indicate that a runaway greenhouse would have occurred early in earth's history had earth been only a few percent closer to the sun. It therefore appears that, taking into account the possibilities of either runaway glaciation or a runaway greenhouse effect, the continuously habitable zone about a solar-type star is rather narrow, extending only from roughly 0.95 to 1.01 AU.
    Keywords: GEOPHYSICS
    Type: Icarus; 33; Jan. 197
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  • 11
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    Geographical variations of NO and O3 in the lower stratosphere (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Nitric oxide and ozone concentrations in the lower stratosphere have been measured from a high-altitude research aircraft using in situ measuring techniques. Results of several geographical surveys are presented along with predictions of two two-dimensional stratospheric models. Meridional and zonal data were obtained in June 1974 and in June, July, and August 1975. At longitudes 122-158 deg W the meridional data taken between 5 and 80 deg N latitude show an increasing NO concentration with latitude, by a factor of 4 at 21-km altitude and a less marked increase at 18 km. The minimum NO concentration at 21 km is observed at 5 deg N latitude and is about 6 x 10 to the 8th power/cu cm. Zonal data at latitudes 22-38 deg N taken from 55 to 176 deg N longitude show little variation of the NO and O3 concentrations with longitude.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Apr. 20
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  • 12
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    Earth's bowshock and its vicinity (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Phenomena associated with the bowshock, such as its thickness, velocity, and associated waves are described. There are transverse waves radiating away from the shock and at times stationary waves fixed to it. Reflected protons generate waves far upstream. Electrostatic waves occur in the shock.
    Keywords: GEOPHYSICS
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  • 13
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    Heat budget of ionospheric electrons (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Heat input calculations were detached from solar extreme UV data and monatomic oxygen densities were derived from simultaneously measured data sets (ion composition 146-191 km) in a study of the heat budget of ionosphere electrons. Earlier inferences that cooling predominates over heating are supported. A search for additional heat sources or a revision of the cooling rates is recommended, by way of balancing the heat budget. Importance is attached to electron cooling by fine structure excitation of monatomic oxygen.
    Keywords: GEOPHYSICS
    Type: Annales de Geophysique; 32; Oct
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  • 14
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    The mesosphere (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The mesosphere is an atmospheric region characterized by a negative gradient of solar energy absorption and temperature. Although the distribution of most minor constituents is dominated by photochemistry, vertical transport does have a pronounced effect on many of them. The basic dynamic principles are discussed along with their application to the important mesospheric motions: acoustic-gravity waves, tides, planetary-scale waves, and eddy motions. Oxides of nitrogen and hydrogen are also examined which strongly influence the balance of odd oxygen (O and O3). Brief discussions of the chemistry of carbon compounds and of excited species are also included. The chemistry of ionic species in the mesosphere is very important because it strongly influences the propagation and absorption of radio waves. Because of ion clustering and negative-ion formation, such chemistry is extremely complex. The current state of knowledge is discussed in some detail. The principles involved in constructing models for predicting the distribution of minor constituents, both neutral and ionic, are presented.
    Keywords: GEOPHYSICS
    Type: Geophysical Surveys; 2; 1976
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  • 15
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    Coincident observations of ionospheric troughs and the equatorial plasmapause (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Electron-density observations made in the topside ionosphere by the Ariel 4 and Isis 2 satellites are examined in conjunction with results obtained by Explorer 45 when it traversed the near-equatorial plasmapause with one hour (both UT and MLT) of the Ariel and Isis traversals of the same L coordinate. Both dusk and night observations are analyzed, and an attempt is made to show that depressions in ionospheric electron density occur in the vicinity of the plasmapause field line. It is concluded that the electron distributions observed in the electron-density troughs at 550 km near dusk by Ariel and at 1400 km near midnight by Isis do not always parallel variations in the light-ion distribution inferred from the Explorer plasmapause traversals and that there appears to be no specific feature of the main ionospheric trough which can be used to identify the plasmapause field line except in a statistical sense.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 24; Dec. 197
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  • 16
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    Some aspects of the stratospheric Cl-ClO-Cl cycle - Possible roles of ClO, ClNO3 and HOCl (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The possible inhibitory effect of excited ClO produced during chlorine-sensitized ozone decomposition on the stratospheric Cl-ClO-Cl cycle is investigated. Collisional deactivation of excited ClO is discussed, chemical reactions involving excited ClO are examined, and the possible roles of HO2 and NO2 in weakening the Cl-ClO-Cl cycle are evaluated. It is noted that the formation of HOCl through a reaction between ClO and HO2 implies that the Cl-ClO-Cl cycle has not been completed.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 24; Dec. 197
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  • 17
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    Effects of the atmosphere on remote sensing (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The interaction between electromagnetic radiation and the earth's atmosphere is considered, taking into account windows in the electromagnetic spectrum, solar and terrestrial radiation, physical properties of the atmosphere, and clouds. The characteristics of upwelling radiation in the visible wavelengths are discussed along with infrared radiation and microwaves. Attention is given to radiant emittance, radiance, contrast, effects of atmospheric turbulence, ocean color, and questions concerning the classification of surface features with the aid of computers.
    Keywords: GEOPHYSICS
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  • 18
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    Magnetospheric whistler ducts observed by ISIS satellites (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The latitudinal width of the magnetospheric whistler duct has been estimated by the first and final invariant latitudes of whistler echoes and the conservation of the magnetic flux for the centered dipole field, using 105 whistler echoes in ISIS VLF data received at Kashima, Japan for 1972-1973. The latitudinal distribution of whistler duct occurrence shows a maximum at invariant latitudes of 40-45 degrees near the maximum occurrence latitude of ground whistlers. The radial width of magnetospheric whistler duct in the geomagnetically equatorial plane increases with invariant latitude of the geomagnetic flux tube in which whistlers propagate.
    Keywords: GEOPHYSICS
    Type: Radio Research Laboratories; vol. 23
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  • 19
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    Terrestrial kilometric radiation. I - Spatial structure studies (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of lunar occultations of earth at 250 kHz, obtained with the Radio Astronomy Explorer 2 satellite, have been used to derive two-dimensional maps of the location of the sources of terrestrial kilometric radiation (TKR). By examining the two-dimensional source distributions as a function of the observer's location (lunar orbit) with respect to the magnetosphere, the average three-dimensional location of the emission regions can be estimated. Although TKR events at 250 kHz can often be observed at projected distances corresponding to the 250-kHz electron gyro or plasma level (about 2 earth radii), many events are observed much farther from earth (about 5 to 15 radii). On the dayside, emission was apparently observed in the region of the polar cusp and the magnetosheath at a magnetic latitude of about 70 deg; in the night hemisphere, emission is found to be associated with regions of the magnetotail at latitudes of at least 70 deg. The nightside emission is suggestive of a mechanism involving plasma-sheet electron precipitation in the premidnight sector.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Dec. 1
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  • 20
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    Thermospheric storms and related ionospheric effects (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A comparative study of thermospheric storms for equinox and winter conditions is presented based on neutral-composition measurements from the Aeros-A neutral-atmosphere temperature experiment. The main features of the two storms as inferred from changes in N2, Ar, He, and O are described, and their implications for current theories of thermospheric storms are discussed. On the basis of the study of the F-region critical frequency measured from a chain of ground-based ionospheric stations during the two storm periods, the general characteristics of the ionospheric storms and the traveling ionospheric disturbances are described. It is suggested that the positive and negative phases of ionospheric storms are different manifestations of thermospheric storms.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Oct. 1
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  • 21
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    Mass spectrometric measurements in the lower thermosphere (1978)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Several types of spectrometers are discussed along with their methods of operations. The open source magnetic deflection type mass spectrometer and the quadrupole mass spectrometer are described in detail. The calibration and mounting procedures used for satellite-borne mass spectrometers were reviewed.
    Keywords: GEOPHYSICS
    Type: Alabama Univ. UAH(NASA Workshop on the Use of a Tethered Satellite System; p 120-129
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  • 22
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    In situ measurement of reactive neutral constituents in the thermosphere by atomic and molecular resonance fluorescence (1978)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Tethered Satellite System in combination with in situ atomic and molecular resonance fluorescence techniques can treat the problem of simultaneously determining the absolute density of atomic and molecular species known to control the photochemical structure of the upper atmosphere. Two familities of reactants which can be treated by these techniques are the nitrogen oxygen family and the hydrogen oxygen family.
    Keywords: GEOPHYSICS
    Type: Alabama Univ. UAH(NASA Workshop on the Use of a Tethered Satellite System; p 111-118
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  • 23
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    Reduction and analysis of satellite magnetometer data (1978)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The broad-scale magnetic anomalies that appear in regional complications of aeromagnetic data, and in regional and global maps are discussed. Satellite data can be of value in defining such anomalies and invaluable, especially when utilized with airborne data, in their interpretation. The reduction and interpretation of satellite magnetometer data differ significantly from the standard techniques that are routinely applied to conventional measurements. The reduction of the data is discussed and its morphology is detailed. Interpretational techniques that are applicable are presented.
    Keywords: GEOPHYSICS
    Type: Alabama Univ. UAH(NASA Workshop on the Use of a Tethered Satellite System; p 59-91
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  • 24
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    Chemical releases (1978)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A Chemical Release Module to be carried into orbit by the shuttle is described. The module would release chemicals from orbiting satellites in order understand processes within the Earth's magnetosphere, atmosphere and ionosphere. A large number of potential experiments are identified, ranging from introducing traceable material into the solar wind in order to study its transport to and within the magnetosphere, to injecting material into the outer magnetosphere to simulate the precipitation of trapped charged particles, to the release of material at lower altitudes to create waves both mechanical and electromagnetic.
    Keywords: GEOPHYSICS
    Type: Alabama Univ. UAH(NASA Workshop on the Use of a Tethered Satellite System; p 135-150
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  • 25
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    Interaction of a tethered satellite with the atmosphere and the resultant environment (1978)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The calibration of apparatus like mass spectrometers under free molecular conditions and the design and execution of relevant calibration experiments in the transition regime in low density wind tunnels is addressed. Potential access to the tethered satellite for beam instrumentation is discussed and would involve aerodynamic design input on the satellite, both as to preferred shape for the experiments and aerodynamic control for up-stream pointing. Aerodynamic design for the purpose of stabilization and pointing is also discussed.
    Keywords: GEOPHYSICS
    Type: Alabama Univ. UAH(NASA Workshop on the Use of a Tethered Satellite System; p 106-110
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  • 26
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    Gravity gradient determination with tethered systems (1978)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A detailed investigation of the Earth's gravity field is needed for application to modern solid earth and oceanic investigations. The use of gravity gradiometers presents a technique to measure the intermediate wavelength components of the gravity field. One configuration of a gradiometer involves a tethered pair of masses orbiting the Earth and stabilized by vertical gravity gradient of the earth. A mesurement of the tension in such a system, called the DUMBBELL system is described. It allows the determination of the vertical gradient of the anomalous component of the Earth's gravtiy field. Preliminary analysis of the dynamics, mechanization, expected signal levels and noise environment indicates that the Dumbbell system is feasible.
    Keywords: GEOPHYSICS
    Type: Alabama Univ. UAH(NASA Workshop on the Use of a Tethered Satellite System; p 33-58
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  • 27
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    The Nimbus 4 infrared spectroscopy experiment. III - Observations of the lower stratospheric thermal structure and total ozone (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Dec. 20
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  • 28
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    Field-aligned currents observed by the Ogo 5 and Triad satellites (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Triad (at a height of 800 km) and Ogo 5 (in the high altitude magnetosphere) magnetic field observations have shown the existence of a field-aligned current system consisting of currents flowing in the polar cap boundary layer and those flowing in another layer located equatorward of the former. In the polar cap boundary layer (identified as the high-latitude boundary of the plasma sheet in the nightside magnetosphere), the current flows into the ionosphere on the morning side and away from the ionosphere on the afternoon side. In the lower-latitude layer, the current directions are reversed. The current in the polar cap boundary layer is considered as the primary field-aligned current system.
    Keywords: GEOPHYSICS
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  • 29
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    Geomagnetic storm effects on the thermosphere and the ionosphere revealed by in situ measurements from OGO 6 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The temporal response of the densities of upper-atmospheric ion and neutral constituents to a particular geomagnetic storm is studied using simultaneous ion and neutral-composition data obtained by the OGO 6 satellite during consecutive orbits at altitudes greater than 400 km. The investigated constituents include H(+), O(+), N2, O, He, and H. Derivation of the H density is reviewed, and the main effects of the storm are discussed, particularly temporal and global variations in the densities. It is found that: (1) the H and He densities began to decrease near the time of sudden commencement, with the decrease amounting to more than 40% of the quiet-time densities during the maximum stage at high latitudes; (2) the O and N2 densities exhibited an overall increase which began later than the change in H and He densities; (3) the H(+) density decreased differently in two distinct regions separated near the low-latitude boundary of the light-ion trough; and (4) the O(+) density showed an increase during earlier stages of the storm and decreased only in the Northern Hemisphere during the recovery phase. Certain physical and chemical processes are suggested which play principal roles in the ionospheric response to the storm
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 24; Nov. 197
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  • 30
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    Diffusive isothermal partitioning in a layered medium with geologic applications (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The diffusive isothermal partitioning of solute in a layered two-phase material has been analyzed to help elucidate the phenomenon of solute partitioning in multiphase lunar and terrestrial materials and to estimate the cooling history of samples. After reviewing the physical chemistry of partitioning and the case of an infinite one-dimensional diffusion couple, we solve in analytic form the case of a finite one-dimensional couple. The solution can be used to estimate cooling histories or to interpret laboratory experiments on partitioning. A sample calculation is included.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Nov. 10
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  • 31
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    On the magnetic mirroring as the basic cause of parallel electric fields (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Among the different proposed mechanisms for generating parallel electric fields, magnetic mirroring of charged particles seems to be the most plausible. In the present paper, it is suggested that magnetic mirroring is the basic cause of parallel electric fields in the magnetosphere and that the magnetic mirroring effect may be able to form the basis of an auroral theory that can remove a major portion of the ambiguity of observations. In the model proposed, the parallel electric field is due to a magnetic confinement of a negatively charged hot collision-free plasma. A transfer of electron gyroenergy into wave energy tends to weaken this confinement; if this energy transfer becomes too strong, the parallel potential gradient will break down. Hence, from this model, in contrast to certain other models of parallel electric fields, only a small fraction of the total auroral particle energy may be expected to be transformed into electromagnetic wave energy during the acceleration process.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Nov. 1
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  • 32
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    Energetics of the midlatitude thermosphere (1976)
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    Publication Date: 2011-08-17
    Description: Thermospheric energetics is examined from the point of view of atomic and molecular processes which convert solar EUV radiative energy into kinetic energy of the ambient electron, ion, and neutral gases. The energy flow from photon to photoelectron-ion pair through energy loss and ion-molecule transfer to eventual electron-ion recombination is traced in detail. Upper and lower bounds are placed on the efficiency of conversion of radiative to thermal energy. Implications for the question of consistency of measured solar EUV fluxes and ionospheric models are discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 38; Aug. 197
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    Dynamical effects in the distribution of helium in the thermosphere (1976)
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    Publication Date: 2011-08-17
    Description: The paper discusses some phenomena, mainly observed by satellites, which illustrate the use of helium as a tracer for studying the morphology and history of atmospheric responses to energy inputs of varying amplitudes and durations. The effects observed include (1) the annual north-south excursion of the sub-solar point producing the winter helium bulge, (2) the 24-hour diurnal variation, where the helium density peak is phase-shifted to the morning in the lower thermosphere, (3) high latitude magnetospheric heating of the thermosphere, with helium indicating regions of probable upwelling of the heated gas, and (4) gravity wave formation and propagation, with the attendant implications for transport of energy from one region of the atmosphere to another.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 38; Aug. 197
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  • 34
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    Algorithms for computing the geopotential using a simple density layer (1976)
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    Publication Date: 2011-08-16
    Description: Several algorithms have been developed for computing the potential and attraction of a simple density layer. These are numerical cubature, Taylor series, and a mixed analytic and numerical integration using a singularity-matching technique. A computer program has been written to combine these techniques for computing the disturbing acceleration on an artificial earth satellite. A total of 1640 equal-area, constant surface density blocks on an oblate spheroid are used. The singularity-matching algorithm is used in the subsatellite region, Taylor series in the surrounding zone, and numerical cubature on the rest of the earth.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Sept. 10
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  • 35
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    Molecular oxygen abundances in the thermosphere from atmosphere Explorer-C ion composition measurements (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Sept. 1
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  • 36
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    V.L.F. emission from ring-current electrons (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Characteristics of VLF emissions detected by satellite in association with enhancements of ring-current electrons during magnetic storms and substorms are described along with the associated enhancements in electron intensities and the anisotropies of the ring-current electron distribution. It is shown that the emissions are observed only when the satellite is outside the plasmasphere, that the beginning of the emissions coincides with the satellite's encounter with the large electron fluxes in that region, and that the increase in electron intensities associated with the observed emissions is limited only to low-energy electrons. The frequency distributions of emissions with peak frequencies above and below half the electron gyrofrequency at the equator is analyzed. The bimodal frequency distribution of the equatorial whistler-mode emissions is explained in terms of different production regions for emissions at frequencies above and below half the equatorial electron gyrofrequency.
    Keywords: GEOPHYSICS
    Type: Nature; 263; Sept. 2
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    Lidar measurement of stratospheric dust from St. Augustine Volcano (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The detection of a stratospheric dust layer of probable volcanic origin over Hampton, Va., on the evening of Jan. 28, 1976, with a 20-inch lidar system is reported. A digitized cathode-ray-tube trace of a return signal from altitudes of 12 to 24 km on January 28 is provided, and it is shown that 38% of the return was due to stratospheric aerosol. Noting that measurements on January 22 and February 2 showed no traces of this stratospheric dust layer, trajectories of dust-laden air parcels are followed from initiation at 0000 GMT on January 24 at the St. Augustine Volcano on Augustine Island, Alaska (59 deg N, 153 deg W). Analysis of the trajectories indicates that dust injected into the stratosphere at 59 deg N, 153 deg W could have been transported to Virginia in about 4 days. It is concluded that if the St. Augustine Volcano was the source of the dust, at least 23 deg of meridional transport from polar latitudes was observed.
    Keywords: GEOPHYSICS
    Type: American Meteorological Society; vol. 57
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  • 38
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    Composition effects in thermospheric gravity waves (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Classical linearized gravity wave theory is employed to derive relationships between amplitude ratios and phase angles of atmospheric constituents undergoing acoustic-gravity wave oscillations. These results are compared with recently reported Atmospheric Explorer-C satellite data. Calculated amplitude and phase characteristics, for a large class of pure internal gravity wave oscillations, are in accord with the AE-C satellite measurements.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Dec. 197
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    OH emission intensity measurements during the 1969 NASA Airborne Auroral Expedition (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Absolute intensity measurements of the (8, 6) OH band obtained during 10 flights of the December 1969 NASA Auroral Airborne Expedition are presented. Nightglow intensities higher by a factor of 2 than the usual values are recorded during flights 8, 14, and 15. The OH variations are compared with the evolution of the green line and O2(1 Delta g) emissions measured by other experimenters on board the aircraft. Before sunrise the twilight variations of OH down to a solar depression angle of 5 deg show a rapid decrease. A theoretical prediction of the OH, O I 5577 A, and O2(1 Delta g) emissions is evaluated by means of an extensive time-dependent oxygen-hydrogen model of the 25- to 150-km region. Twilight decrease of the OH emission is interpreted in terms of mesospheric ozone photodissociation. Nighttime variations of the emissions may be reproduced if modifications of the dynamic regime are introduced into the model.
    Keywords: GEOPHYSICS
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  • 40
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    Topside optical view of the dayside cleft aurora (1976)
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    Publication Date: 2011-08-17
    Description: Photometers on the ISIS-II spacecraft provide a view of the atomic oxygen 5577-A and 6300-A emissions and the N2(+) 3914-A emission detected as dayside aurora in the magnetospheric cleft region. The 6300-A emission forms a continuous and permanent band across the noon sector, at about 78 deg invariant latitude, with a defined region of maximum intensity that is never less than 2 kR (uncorrected for albedo) and is centered near magnetic noon. There are significant differences in the intensity patterns on either side of noon and their responses to geomagnetic activity. Discrete 3914-A auroral forms appear within this region at preferred locations that cannot be precisely specified but which tend to the poleward edge of the 6300-A emission in the evening and the equatorward edge in the morning, where the difference between the two emissions is greatest. It is concluded that the discrete auroras observed by all-sky cameras in the day sector follow the 6300-A emission through the cleft region, though a definite cleft boundary is not defined.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 24; Oct. 197
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  • 41
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    Effect of nearby supernova explosions on atmospheric ozone (1976)
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    Publication Date: 2011-08-16
    Description: An investigation has been conducted of the probable effects of a nearby supernova event on the ozone layer of the earth. It is found that the ozone depletion, although smaller than that estimated by Ruderman (1974), is still significant, and could, as a result of cosmic rays, extend over periods of time from 1000 to 10,000 years. However, the probability of the occurrence of such an event within the past 100 million years appears to be low. The calculated ozone depletion seems to be the major effect of a supernova on a earth-like planet at a distance in the range from 5 to 10 pc.
    Keywords: GEOPHYSICS
    Type: Nature; 263; Sept. 30
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  • 42
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    Evolution of the ionosphere (1976)
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    Publication Date: 2011-08-16
    Description: Studies were made of the electron density profiles at various stages of atmospheric evolution, with the assumption that the atmospheric composition has changed due to the gradual increase of oxygen while the nitrogen level has remained constant. The result of model calculations indicates that when the oxygen content is less than about 1% of the present earth's atmosphere level, the major ions in the F2 region will change from O(+) to N(+). The maximum number density of N(+) ions reaches approximately 10 million per cu cm because of the absence of a rapid loss mechanism for N(+). The height of the N(+) ion density peak is much lower than the height of the F2 layer peak of the current ionosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Sept. 1
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  • 43
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    Ion chemistry of N2/+/ and the solar ultraviolet flux in the thermosphere (1976)
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    Publication Date: 2011-08-16
    Description: We have analyzed daytime composition measurements in the thermosphere from Atmosphere Explorer-C by use of a theory of the ion chemistry. Predicted and measured N2(+) densities are compared to infer global variation of the solar ionizing flux. Results indicate that the solar flux of Hinteregger measured on Atmosphere Explorer-C provides an adequate basis for the calculation of solar ultraviolet photoionization rates. The role of metastable species is examined, and theoretical O+(2D) densities are presented.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Aug. 1
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  • 44
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    The interpretation of ionospheric radio drift measurements. IX - Direct comparisons between field-aligned ion drifts by incoherent scatter and Kinesonde measurements (1976)
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    Publication Date: 2011-08-16
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 38; July 197
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  • 45
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    Representation of magnetic fields in space (1976)
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    Publication Date: 2011-08-16
    Description: Several mathematical methods which are available for the description of magnetic fields in space are reviewed. Examples of the application of such methods are given, with particular emphasis on work related to the geomagnetic field, and their individual properties and associated problems are described. The methods are grouped in five main classes: (1) methods based on the current density, (2) methods using the scalar magnetic potential, (3) toroidal and poloidal components of the field and spherical vector harmonics, (4) Euler potentials, and (5) local expansions of the field near a given reference point. Special attention is devoted to models of the magnetosphere, to the uniqueness of the scalar potential as derived from observed data, and to the L parameter.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 14; May 1976
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  • 46
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    Stratospheric ozone as viewed from the Chappuis band (1976)
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    Publication Date: 2011-08-16
    Description: Total stratospheric ozone values above high-altitude stations in southern California from 1912 to 1950 and northern Chile from 1918 to 1948 are determined using data obtained by the Smithsonian Astrophysical Observatory, including transmission measurements made in the Chappuis band (0.5 to 0.7 micron). The results show that at both sites, total ozone amounts commonly exhibit variations of as much as 20% to 30% on time scales ranging from months to decades. Consideration of the amount of incident solar energy absorbed by the Chappuis band suggests that ozone acts as a shutter on the incoming solar radiation and provides a trigger mechanism between solar activity and climatic change.
    Keywords: GEOPHYSICS
    Type: Nature; 261; May 27
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  • 47
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    Effect of temperature coupling on ozone depletion prediction (1978)
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    Publication Date: 2011-08-17
    Description: The effects of chlorine perturbations on both the temperature and the ozone distribution in the stratosphere have been studied using a simplified radiative-photochemical model. The model solves the hydrostatic equation for total density in a self-consistent manner as the temperature is changed. Radiative coupling is found to have a significant effect on both the thermal structure and the ozone distribution, particularly in the 35-50-km region. By increasing the ClX mixing ratio by 5.0 ppbv, the temperature in this region is decreased by 5 to 10 K with a slight increase below 30 km. The local ozone depletion around 40 km due to added ClX is smaller compared with the estimate made by keeping the temperature fixed to the ambient condition. However, the integrated effect of radiative coupling is to increase the calculated column ozone depletion by 15% to 25% in this model.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 5; Mar. 197
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  • 48
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    The signature of H/+/ in the equatorial anomaly - An empirical model (1978)
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    Publication Date: 2011-08-17
    Description: Ion composition data from the OGO-6 satellite are used to develop an empirical model of the H(+) signature in the equatorial anomaly. The empirical model is an attempt to represent the generally repeatable details of the satellite data by a parameterized numerical model accounting for such variables as the altitude, local time and longitude of the observations. Although the resulting model is in general agreement with past findings on the variability of the equatorial anomaly phenomenon, there appears to be a complexity of short-term or narrowly localized variations which cannot be adequately understood on the basis of data from a single satellite.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 16; May 1978
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  • 49
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    Stratospheric nitric oxide and ozone measurements using photoionization mass spectrometry and UV absorption (1978)
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    Publication Date: 2011-08-17
    Description: Nitric oxide has been measured in situ between 38.4 and 29.8 km by a new technique, photoionization mass spectrometry. Data indicate a peak mixing ratio of 5.7 plus or minus 0.35 ppbv at 37.5 km and only 0.2 plus or minus 0.2 ppbv at 32.8 km with a sharp gradient in concentration between 33 and 34 km. Simultaneous in-situ measurements of the ozone concentration show no significant feature at that altitude. The rapid decrease in mixing ratio is not predicted by current theory.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 5; Jan. 197
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  • 50
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    Nitric oxide formation by meteoroids in the upper atmosphere (1976)
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    Publication Date: 2011-08-16
    Description: The process of nitric oxide formation during atmospheric entry of meteoroids is analyzed theoretically. An ablating meteoroid is assumed to be a point source in a uniform flow with a continuum regime evolving in its wake. The amount of nitric oxide produced by high-temperature reactions of air in the continuum regime is calculated by numerical integration of chemical-rate equations. The results, when summed over the observed mass, velocity, and entry-angle distributions of meteoroids, provide annual global production rates of nitric oxide as a function of altitude. The peak production of nitric oxide is found to occur at altitudes between 90 and 100 km, the total annual rate being about 40 million kg. The present results suggest that the large concentration of nitric oxide observed below 95 km could be attributed to meteoroids instead of photodissociation of nitrogen.
    Keywords: GEOPHYSICS
    Type: Atmospheric Environment; 10; 7, 19; 1976
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    Field-aligned fluxes in the geomagnetic equator (1976)
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    Publication Date: 2011-08-16
    Description: During 12 electron injection events observed by Explorer 45 during the December, 1971, and February, 1972, in magnetic storms it was found that the lowest observable pitch angle particles (down to 7 degrees in one case) arrived first. Pitch angle dispersion and shell-splitting effects are shown to be inadequate explanations for most of these pitch angle distributions. It is suggested that parallel electric fields may be supplying 1- to 5-keV electrons to the magnetosphere from the ionosphere. Various models of parallel electric fields are discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Apr. 1
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    Cyclotron side-band emissions from ring-current electrons (1976)
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    Publication Date: 2011-08-16
    Description: The paper examines temporal variations in electron energy spectra and pitch-angle distributions during a VLF-emission event observed by Explorer 45 in the main phase of a magnetic storm. It is noted that the observed event occurred outside the plasmasphere on the night side of the magnetosphere and that the dusk-side plasmapause had a double structure during the event. It is found that the VLF emissions consisted of two frequency bands, corresponding to the whistler and electrostatic modes, and that there was a sharp band of 'missing emissions' along frequencies equal to half the equatorial electron gyrofrequency. A peculiar pitch-angle distribution for high-energy electrons (50 to 350 keV) is noted. It is concluded that the VLF-producing particles were enhanced low-energy (about 5 keV) ring-current electrons which penetrated into the night side of the magnetosphere from the magnetotail plasma sheet and which drifted eastward after encountering the steep gradient of the geomagnetic field.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 24; Apr. 197
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    Deuteron whistler and trans-equatorial propagation of the ion cyclotron whistler (1976)
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    Publication Date: 2011-08-16
    Description: The paper investigates two unusual types of ion cyclotron whistlers that were found in the low-latitude topside ionosphere by analyzing ISIS VLF electric-field data received at Kashima, Japan. One type is characterized by an asymptotic frequency equal to one half the local proton gyrofrequency; the asymptotic frequency of the other type corresponds to the minimum proton gyrofrequency along the geomagnetic field line passing through the satellite. The observations are compared with theoretical spectrograms of the ion cyclotron whistlers computed for appropriate model distributions of electrons and ions in the topside ionosphere. It is found that the whistlers with the asymptotic frequency of one half the local proton gyrofrequency are deuteron whistlers and that the other whistlers are due to the transequatorial propagation of proton or deuteron whistlers originating in the southern hemisphere.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 24; Apr. 197
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    The gravitational wave detection experiment: Description and anticipated requirements (1978)
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    Publication Date: 2011-08-17
    Description: The experiment to detect gravitational waves in ultraprecise two-way Doppler data is described, as are the anticipated requirements for the Deep Space Network, the spacecraft, and the data processing system. The special feature which allows the usage of ultraprecise Doppler data for the possible detection of gravitational waves is a unique three-pulse signature which is a function of the spacecraft, earth, and gravitational wave propagation direction geometry. The pulses (fractional frequency shifts) result from effects which are conveniently described as follows: Clock speed-up (earth only effect) and buffeting (equal earth and spacecraft effect).
    Keywords: GEOPHYSICS
    Type: The Deep Space Network; p 100-108
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    A parameterization for the absorption of solar radiation by water vapor in the earth's atmosphere (1976)
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    Publication Date: 2011-08-16
    Description: A parameterization for the absorption of solar radiation as a function of the amount of water vapor in the earth's atmosphere is obtained. Absorption computations are based on the Goody band model and the near-infrared absorption band data of Ludwig et al. A two-parameter Curtis-Godson approximation is used to treat the inhomogeneous atmosphere. Heating rates based on a frequently used one-parameter pressure-scaling approximation are also discussed and compared with the present parameterization.
    Keywords: GEOPHYSICS
    Type: Journal of Applied Meteorology; 15; Jan. 197
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    Composition waves in the thermosphere (1976)
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    Publication Date: 2011-08-16
    Description: Neutral-composition waves excited by auroral heat sources are investigated. For horizontal wavelengths of the order of 1000 km, it is concluded that diffusion processes (1) play a significant role such that deviations from diffusive equilibrium prevail for He throughout the thermosphere; (2) produce phase differences of about 220 deg (or -140 deg) between He and N2, and (3) account for He amplitudes comparable to those of N2. These results basically explain recent AE-C satellite measurements which have revealed an anticorrelation between the heavier and lighter constituents of the thermosphere. The calculations also indicate that temperature and N2 concentration are generally out of phase by about 100 deg.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Feb. 1
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    Apollo 16 far ultraviolet imagery of the polar auroras, tropical airglow belts, and general airglow (1976)
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    Publication Date: 2011-08-16
    Description: Far-ultraviolet imagery of the earth in the wavelength ranges from 1050 to 1600 A and from 1250 to 1600 A was obtained from the lunar surface during the Apollo 16 mission on Apr. 21, 1972. The images have an angular resolution of about 2 arcmin (230-km linear resolution) and have been quantitatively analyzed to obtain absolute intensities and spatial distributions of the polar auroras (both wavelength ranges), the day and night airglow, and tropical airglow belts (1250-A to 1600-A wavelength range). The observations are consistent with previous results obtained from the OGO-4 spacecraft, but they have also provided details on the spatial distributions of the various emissions over an entire hemisphere at a single time. A general night airglow, at least in the Northern Hemisphere, is indicated.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Feb. 1
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    Perturbation theory in thermosphere dynamics (1976)
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    Publication Date: 2011-08-16
    Description: It is shown that density and pressure throughout the thermosphere can be adequately described in a logarithmic expansion that provides a sound basis for the application of perturbation theory. This expansion eliminates most of the important nonlinearities associated with density variations. On the basis of this expansion, the validity of perturbation theory can be extended to cover a large variety of atmospheric conditions in which the relative temperature amplitude is less than 0.5 and wind velocities are significantly less than the speed of sound.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Mar. 1
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    Wind-enhanced escape with application to terrestrial helium (1976)
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    Publication Date: 2011-08-16
    Description: We derive a simple expression for the escape flux which takes into account horizontal winds at the exobase. The escape flux is shown to increase with the wind velocity and becomes much larger than the Jeans escape flux for velocities approaching the thermal velocity. This model is applied to terrestrial He-4, where we determine the conditions required for wind-enhanced escape to contribute to the overall He-4 budget. For completeness, we also derive an expression for the escape flux when only a vertical wind is present at the exobase.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Mar. 1
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    Magnetic fields of the magnetosheath (1976)
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    Publication Date: 2011-08-16
    Description: The magnetic field of the magnetosheath is most naturally discussed in terms of its steady state and its fluctuating components. The theory of the steady-state field is quite well developed, and its essential features have been confirmed by observations. The interplanetary field is convected through the bow shock, where its magnitude is increased and its direction changed by the minimal amount necessary to preserve the normal component across the shock. Convection within the magnetosheath usually increases the magnitude still further near the subsolar point and further distorts the direction until the field is aligned approximately tangent to the magnetopause. Fluctuations of the magnetosheath field are very complex, variable, and not well understood. Transverse waves are often dominant at frequencies below 0.002 Hz, and compressional waves are often dominant at somewhat higher frequencies. Perturbation vectors of hydromagnetic waves tend to be aligned with the shock and magnetopause surfaces. Magnetosheath waves may be generated upstream, within the magnetosheath, at the bow shock, or at the magnetopause.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 14; Feb. 197
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    A comparison of one-dimensional theoretical models of stratospheric minor constituents (1976)
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    Publication Date: 2011-08-16
    Description: The density profiles of stratospheric minor constituents are compiled from several one-dimensional theoretical models that have appeared in the literature. The models are compared with each other and also with observations if data are available. The similarity and disparity of the models are clarified and discussed. If a large difference exists among the models, attempts are made to interpret it as much as possible in terms of the physical and chemical data employed in each model. The inadequacy of one-dimensional models in calculating the realistic ozone density distributions and the problems related to it are briefly discussed.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 14; Feb. 197
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    Diurnal and seasonal variations in atomic and molecular oxygen inferred from Atmosphere Explorer-C (1976)
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    Publication Date: 2011-08-16
    Description: Mass-spectrometer measurements of O and N2, obtained with the Atmosphere Explorer-C satellite during December 1974 and January 1975, are used to derive the O2 concentration near 250 km from several ionization reactions. In order to separate temperature effects from diffusion effects, the measured O and inferred O2 concentrations are employed to determine, under the assumption of diffusive equilibrium, the O/N2 and O2/N2 ratios at 120 km. It is found that the latitudinal and diurnal variations in the O concentration at 120 km are consistent with previous results obtained with OGO 6 and that the O2 concentration in the Northern (winter) Hemisphere is about twice as high as that in the Southern (summer) Hemisphere. The possible importance of photodissociation in the diurnal O2 variations is discussed.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Feb. 197
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  • 63
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    High-latitude troughs and the polar cap boundary (1976)
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    Publication Date: 2011-08-16
    Description: OGO 6 observations of troughs in the thermal plasma densities in the topside ionosphere are discussed. Ion mass spectrometer measurements were correlated with energetic electron detector and electric field measurements. It is shown that the variation of ion composition at high latitudes is complex and frequently characterized by mid-latitude and high-latitude density depression. Prominent high-latitude troughs in the atomic ion (H, He, O) distributions were seen to lie frequently near the polar cap boundary. This indicates that these troughs are unrelated to the plasmapause which is found on closed magnetic field lines away from the trapping boundary. The production of the high-latitude troughs is shown to be related to enhancements in the soft electron flux and/or to the convection electric field.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Feb. 1
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  • 64
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    Satellite measurements of ion composition and temperatures in the topside ionosphere during medium solar activity (1976)
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    Publication Date: 2011-08-16
    Description: Information on both ion density and temperature is obtained from analysis of Retarding Potential Analyzer data from the OGO-4 and Explorer-31 satellites. Results obtained from data in the altitude range of 700-2000 km during medium solar activity are presented. An attempt is made to describe the major altitude variations of ion densities and temperatures at middle and low latitudes. The transition heights, where the heavier and lighter ions are equal, are found to be about 1600 and 1300 km at middle and low latitudes, respectively, for daytime and 700 km at night for middle latitudes. Based on the observed data and using diffusive equilibrium as a first-order approximation, topside ionospheric composition models are given for medium solar activity.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 38; Apr. 197
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  • 65
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    Rb, Sr and strontium isotopic composition, K/Ar age and large ion lithophile trace element abundances in rocks and glasses from the Wanapitei Lake impact structure (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Shock metamorphosed rocks and shock-produced melt glasses from the Wanapitei Lake impact structure have been examined petrographically and by electron microprobe. Eleven clasts exhibiting varying degrees of shock metamorphism and eight impact-produced glasses have been analyzed for Rb, Sr and Sr isotopic composition. Five clasts and one glass have also been analyzed for large ion lithophile (LIL) trace element abundances including Li, Rb, Sr, and Ba and the REE's. The impact event forming the Wanapitei Lake structure occurred 37 m.y. ago based on K/Ar dating of glass and glassy whole-rock samples. Rb/Sr isotopic dating failed to provide a meaningful whole-rock or internal isochron. The isotopic composition of the glasses can be explained by impact-produced mixing and melting of metasediments.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta; 40; Jan. 197
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  • 66
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    Absorption cross sections of some atmospheric molecules for resonantly scattered O I 1304-A radiation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Absorption cross sections for O2, N2, CO2, CH4, N2O, and CO have been measured at each of the lines of the atomic oxygen triplet at 1302, 1305, and 1306 A. Radiation resonantly scattered from oxygen atoms at a temperature of about 300 K was used for the line source. Absorber temperatures were also near 300 K. Direct application of the Lambert-Beer absorption equation yielded pressure-dependent cross sections for carbon monoxide at each line of the O I triplet. Reasons for this apparent dependence are presented and discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; July 1
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  • 67
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    Tests and comparisons of satellite-derived geoids with Skylab altimeter data (1976)
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    Publication Date: 2011-08-16
    Description: During the Skylab 4 mission, the S-193 radar altimeter was operated nearly continuously for a revolution around the world on Jan. 31, 1974. This direct measurement to the sea surface has provided an independent basis for the evaluation of the precision of global geoids computed from satellite-derived earth gravity models. This paper presents comparisons between the Skylab data and several recent gravity models published by Goddard Space Flight Center, the Smithsonian Astrophysical Observatory, and the National Oceanic and Atmospheric Administration. The differences between the altimeter geoid and the satellite geoids were as large as 20 m, rms values ranging from 8 to 10 m. These differences also indicated a systematic long-wavelength variation (about 100 deg) not related to error in the Skylab orbits. Truncation of the models to degree and order 8 did not eliminate the long-wavelength variation, but in every case the rms agreement between the satellite geoids and the altimeter geoid was slightly improved. Orbits computed with the truncated models were found to be inferior to those computed with the complete models.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; July 10
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  • 68
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    On the origin of ringing irregularities - A meteor hypothesis (1978)
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    Publication Date: 2011-08-17
    Description: Isolated ionospheric irregularities produce oscillating diffraction patterns on the ground. In the present study typical physical properties such as density, size, etc. of these irregularities are estimated on the basis of diffraction pattern characteristics. These properties agree well with those of meteor trail ionization and it has been found that most of these oscillating irregularities occur on meteor shower days. It is therefore suggested that the oscillating irregularities are caused by meteor showers.
    Keywords: GEOPHYSICS
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  • 69
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    Charge exchange lifetimes for ring current ions (1978)
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    Publication Date: 2011-08-17
    Description: In view of the importance of charge exchange decay as a loss mechanism for magnetospheric ions, the paper summarizes the latest and best measurements of the physical quantities involved in the calculation of the charge exchange lifetime of the mirroring ions. The normalized atomic hydrogen distribution is presented as a function of radial distance on the basis of the Chamberlain model for a range of exobase temperatures and for various combinations of satellite particles. Cross section measurements for various ions in the energy range 1 keV to 200 keV are summarized in the form of normalized charge exchange lifetimes. The equatorial lifetimes can be determined for any of these ions at a specific energy and L-value.
    Keywords: GEOPHYSICS
    Type: Space Science Reviews; 22; Aug. 197
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  • 70
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    Faraday rotation measurements at Ootacamund (1978)
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    Publication Date: 2011-08-17
    Description: The results of Faraday rotation measurements made at Ootacamund during ATS-6 phase II are presented. For summer and equinoctial months, even though no clear noon bite-out is observed in the variation of Faraday a decrease is observed in the rate of increase of rotation around 0900-1000 hours LT. This is attributed to the 'fountain effect' which is responsible for the noontime bite-out in F2-region peak electron density.
    Keywords: GEOPHYSICS
    Type: Indian Journal of Radio and Space Physics; 7; June 197
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  • 71
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    A numerical model for low-latitude ionospheric TEC (1978)
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    Publication Date: 2011-08-17
    Description: A numerical model of total electron content (TEC) at low latitudes has been constructed from the Faraday rotation data recorded at a number of locations in India during the period Oct. 1975-July 1976 when the geostationary satellite ATS-6 was located at 35 deg E. In all, 36 coefficients for each season are required to represent the model. The model can be used for satellite tracking systems in estimating quickly the range, range rate and angular refraction errors. The present model is an improvement over the previously constructed model based on orbiting satellite data.
    Keywords: GEOPHYSICS
    Type: Indian Journal of Radio and Space Physics; 7; June 197
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  • 72
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    The viscoelastic stiffness model of seismicity (1978)
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    Publication Date: 2011-08-17
    Description: A viscoelastic stiffness model of seismicity is developed by introducing a viscoelastic element into the stiffness model for fault dynamics. The introduction of this element permits modeling of transient anelastic deformations in response to stress loading and relaxation and provides a mechanism for partial stress recovery following an earthquake. As a consequence, several phenomena not present in elastic stiffness theory emerge. These include postseismic creep, foreshocks, and aftershocks. Numerical simulations of fault motion also reveal episodes of stable sliding, tertiary creep preceeding earthquakes, and long-term aseismic creep.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Nov. 10
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  • 73
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    The high-latitude winter F region at 300 km - Thermal plasma observations from AE-C (1978)
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    Publication Date: 2011-08-17
    Description: Results are presented for a comprehensive survey of thermal ion composition and electron temperature (Te) variations in the southern high-latitude winter F region near 300-km altitude. The data are obtained from the Atmosphere Explorer (AE-C) satellite during a magnetically quiet period centered on the June 1976 solstice. Prominent ionospheric features, including the nightside main trough, a high-latitude ionization hole, and the dayside auroral zone-cusp region, are characterized in terms of composition and Te variations. The structures under study are qualitatively interpreted in terms of known processes.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Oct. 1
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  • 74
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    Fe/+/ ions in the high latitude F-region (1978)
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    Publication Date: 2011-08-17
    Description: Ion mass-spectrometer measurements on Atmosphere Explorer C orbits from December 1974 to December 1976 were surveyed poleward of + or - 30 deg for instances in which the Fe(+) number density exceeded the spectrometer threshold sensitivity of 30/cu cm. The occurrences of Fe(+) within the altitude range covered by the orbit, 220 to 320 km, revealed a distinct pattern apparently associated with regions of upward plasma transport. At night a band of such events occurred between 50 and 60 deg invariant latitude, which typically corresponded to the location of the main ionospheric trough. In this region large upward ion drifts due to the drag of an equatorward-blowing neutral wind are expected. The Fe(+) band extends past 0600 MLT to about 1100 MLT during the summer, but is not observed in the afternoon. The dayside distributions possibly result from the upward drifts of F-region ions detected by backscatter techniques after dawn during summer. At higher latitudes patches of Fe(+) were detected in regions where strong plasma drifts often prevail and hence where poleward E x B drift motions and atmospheric expansion through Joule heating can lift the ions upwards.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 5; Sept
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  • 75
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    The noon and midnight mid-latitude trough as seen by Ariel 4 (1978)
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    Publication Date: 2011-08-17
    Description: The electron density data returned by the polar orbiting satellites Ariel 3 and Ariel 4 revealed that the midlatitude trough is one of the distinct large-scale features of the ionosphere at about 550 km. Recent work (e.g., Tulunay and Grebowsky, 1975) on the data included the investigation of the temporal development of the latitudinal position of the midlatitude electron density trough at dawn and dusk during the large magnetic storms of May 1967 and May 1972. Model calculations which assumed that the equatorial convection E-field varies in step with the Kp index reproduced on the average the observed behavior. In the present paper, trough observations made at noon and midnight during the period, 12-21 December 1971 which encompassed a relatively large magnetic storm are discussed. In this context, model calculations have been employed as a guide of average approximations of the actual situation in predicting the plasmapause location. It is also shown that the trough observed on the noon passes is not generally plasmapause-related as the nightside troughs are expected to be.
    Keywords: GEOPHYSICS
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  • 76
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    The accuracy of geopotential models (1978)
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    Publication Date: 2011-08-17
    Description: The accuracy of two recent geopotential models, GEM 7 and GEM 8, is evaluated and is found to be about 4.3 m with respect to the global geoid surface for GEM 7 and 3.9 m for GEM 8. The accuracies are root mean square values obtained by the use of 400 coefficients for GEM 7 and 706 coefficients for GEM 8. Independent observations used in the evaluation include 159 lumped coefficients from 35 resonant orbits, two sets of fields derived from optical-only and laser-only data, sets of zonal and resonant coefficients, and geoid undulations. The ratio of estimated commission to formal error in GEM 7 and GEM 8 ranges from 2 to 5. Several other recent geopotential models are examined.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 26; Dec. 197
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  • 77
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    Determination of the geocentric gravitational constant from laser ranging on near-earth satellites (1978)
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    Publication Date: 2011-08-17
    Description: Laser range observations taken on the near-earth satellites of Lageos (a = 1.92 e.r.), Starlette (a = 1.15 e.r.), BE-C (a = 1.18 e.r.), and Geos-3 (a = 1.13 e.r.) have been combined to determine an improved value of the geocentric gravitational constant (GM). The value of GM is 398600.61 cu km/sec per sec, based upon a speed of light, c, of 299792.5 km/sec. Using the IAG-adopted value of c equalling 299792.458 km/sec scales GM to 398600.44 cu km/sec per sec. The uncertainty in this value is assessed to be plus or minus 0.02 cu km/sec per sec. Determinations of GM from the data taken on these four satellites individually show variations of only .04 cu km/sec per sec from the combined result. The Lageos information dominated the combined solution, and gave the most consistent results in its data subset solutions. The value obtained for GM from near-earth laser ranging compares quite favorably with the most recent results of the lunar laser and interplanetary experiments.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 5; Dec. 197
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  • 78
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    Performance characteristics of the electrochemical concentration cell ozonesonde (1978)
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    Publication Date: 2011-08-17
    Description: A large number of electrochemical concentration cell (ECC) ozonesondes were calibrated in relation to a UV photometric absorption ozone instrument prior to using the ozonesondes in atmospheric soundings. The two methods of measuring ozone were in reasonable agreement on the average, but there was considerable variation from one ozonesonde to another. Averaging the individual linear regressions gives an ECC ozone concentration equal to 0 + or - 8 nbar plus (0.96 + or - 0.10) times the concentration determined with the UV instrument, where uncertainties represent 90% confidence limits. Applying individual calibration corrections to atmospheric sounding data reduced the mean difference between Dobson spectrophotometric measurements of total ozone overburdens and corresponding values obtained from ozonesonde data from -8.5 + or - 8.2 to -1.4 + or - 7.3% for a series of measurements carried out in 1977. Corresponding uncorrected and corrected differences averaged 3.2 + or - 9.7 and 1.9 + or - 10.6%, respectively, for soundings carried out in 1976.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Nov. 20
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  • 79
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    High correlations between variations in monthly averages of solar activity and total atmospheric ozone (1978)
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    Publication Date: 2011-08-17
    Description: Estimates of the ozone total columnar content, derived from Nimbus IV IRIS data, have been analyzed to estimate monthly averages of the total global atmospheric ozone. Over a 9-month interval, the variation in this monthly average is approximately an order of magnitude greater than its associated uncertainty, and has characteristics in common with variations in the 10.7 cm solar flux, the Zurich sunspot number, and the total solar Lyman alpha flux. The highest correlation, 0.94, exists between the variation in the total Lyman alpha flux and the variation in the estimated total atmospheric ozone.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 5; Nov. 197
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  • 80
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    Some properties of upper atmosphere dynamics (1978)
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    Publication Date: 2011-08-17
    Description: A unifying description is provided of some important dynamic properties of the upper atmosphere in composition and temperature characteristic of a variety of phenomena, including diurnal and seasonal tides, magnetic storms, and momentum coupling with the magnetosphere. A theoretical multiconstituent model is used which can link the large-scale variations of composition and temperature to the dynamics and energetics of the thermosphere. Global mean properties of the thermosphere are reviewed, and an attempt is made to convey some understanding of the dynamic properties of energy and diffusive mass transport in the thermosphere. Attention is given to sources of energy for the thermosphere, the transport processes involved in the solar diurnal tide of the thermosphere, energy and particle sources for the annual tide, feedback from composition changes to wind-field and temperature variations, energy deposition in the thermosphere during magnetic storms and substorms, and momentum source signatures in the thermosphere.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics; 16; Nov. 197
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  • 81
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    Effect of the reaction HO2 + O3 yields OH + 2O2 on stratospheric ozone (1978)
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    Publication Date: 2011-08-17
    Description: It is noted that recent measurements of large values of the rate coefficient for the reaction NO + HO2 yields NO2 + OH lead to model predictions of excessive amounts of stratospheric ozone. This letter shows that a recent measurement of the rate coefficient (k2) for the reaction HO2 + O3 yields OH + 2O2 largely resolves these problems of excessive stratospheric ozone in models. A two-dimensional model of stratospheric trace constituents is used to calculate the concentrations of 35 constituents; the results are compared with experimental measurements of ozone column densities. It is found that the model predictions of excess ozone abundances diminish significantly when the measured value of k2 is employed.
    Keywords: GEOPHYSICS
    Type: Nature; 275; Oct. 12
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  • 82
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    Imp 6 measurements in the distant polar cusp during substorms (1978)
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    Publication Date: 2011-08-17
    Description: High time-resolution data from the magnetic field, plasma, energetic particle, and VLF wave experiments performed aboard Imp 6 in a study of the distant dayside cusp during substorms are described. The cusp was studied when its location was slightly equatorward of its normal location and the geomagnetic dipole was tilted in the appropriate direction. The data support both reconnection and diffusion as methods of particle entry to the magnetosphere. The evidence (1) indicates an acceleration process to explain enhancements of 400 to 600-km/sec protons above their magnetosheath intensities, and (2) suggests convection of field lines over the polar cap as a means of explaining the lack of low-energy protons near the low-latitude boundary of the cusp. Magnetic field fluctuations, a perturbation vector, ion cyclotron waves, and an abrupt change in the intensity of both whistler waves and electrostatic waves are characterized.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Sept. 1
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  • 83
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    Topside sounder observations of equatorial bubbles (1978)
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    Publication Date: 2011-08-17
    Description: Large scale regions of depleted equatorial ionospheric plasma, called equatorial bubbles, are investigated using topside sounder data. The sounder's unique remote measuring capability enables the magnetic field-aligned nature of the bubbles to be investigated. A search of all available Alouette 2 and ISIS 1 ionograms during nighttime perigee passes near the magnetic equator has revealed a variety of echo signatures associated with bubbles. In addition to a sudden drop in electron density, these signatures usually include in situ spread F and ducted traces. The ducted traces have been used to determine the electron density distribution and to infer changes in ion composition along the magnetic field line within the duct associated with the bubble. In some cases it can be determined that the bubble is asymmetric with respect to the magnetic equator. Even though such features require 3 dimensional models for their explanation, the great field-aligned extent of the bubbles (relative to their cross section) suggests that current theories, which ignore variations along the magnetic field, are still applicable.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 5; Sept
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  • 84
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    Some characteristics of electric field momentum coupling with the neutral atmosphere (1978)
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    Publication Date: 2011-08-17
    Description: A three-dimensional model has been developed to describe momentum coupling between high-latitude electric fields, neutral winds, temperature, and composition. The Hall drag is found to be the main source for atmospheric winds and the small divergence component of winds is due to the Pedersen drag and the Hall drag. Adiabatic heat transfer is responsible for the back pressure which damps the divergence field and for the reversal in circulation of the divergence field at higher altitudes. Back pressure causes a decrease in total wind velocity of about 10% at exospheric heights and by a factor of about 2 at 120 km. The wind field with the pressure feedback may be simulated by neglecting pressure variations and the Coriolis force. Density variations of Ar, N2, O, and He, induced by the momentum source, are in phase above 120 km and out of phase with the temperature amplitude above 150 km. The electrostatic field momentum source is ineffective for directly inducing density and temperature variations in the upper thermosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; July 1
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  • 85
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    Direct evidence of transport processes in the thermospheric diurnal tide (1978)
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    Publication Date: 2011-08-17
    Description: Measurements of neutral composition and temperature obtained between December 6, 1975, and September 17, 1976, with instruments aboard the near-equatorial AE-E satellite are analyzed to determine the diurnal variations at altitudes from 145 to 295 km. The general trends, including the shift in oxygen phase from afternoon at high altitudes to morning at low altitudes, are reproduced by circulation theories. The oxygen and helium variations show small departures from diffusive equilibrium below 200 km that are consistent with wind-induced diffusion and provide the first direct evidence of transport processes in the diurnal tide of the thermosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; July 1
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  • 86
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    A comparison of measured and inferred temperatures from AEROS-B (1976)
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    Publication Date: 2011-08-17
    Description: The neutral composition and the temperature data obtained from the AEROS-B Neutral Atmosphere Temperature Experiment (NATE) and the Neutral and Ion Mass Spectrometer (NIMS) are compared, and the general validity of inferring gas temperatures from N2 and Ar density profiles is examined by comparing them with the in situ measured values of the neutral kinetic temperature (NATE). At times serious discrepancies are noted between the inferred and the measured temperature. This is particularly evident during periods of increased magnetic activity when the normally observed latitudinal variations are apparently modulated by waves propagating from the polar region to low latitudes. Under these conditions the N2 and Ar densities and temperature oscillations are usually out of phase, and the temperatures inferred from N2 and Ar at a given point become meaningless.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Dec. 197
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  • 87
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    Quasi-biennial geomagnetic variation caused by the sun (1976)
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    Publication Date: 2011-08-17
    Description: Clear evidence for the existence of a quasi-biennial geomagnetic variation is shown by an analysis of annual averages of the horizontal (H) component of the geomagnetic field observed at five observatories. The analysis uses a numerical filter, which is equivalent to taking the second order time derivative of the time series. The cause for the variation is external to the earth because its amplitude depends on magnetic activity. The second order time derivative of H is well correlated with the corresponding time derivatives of the relative sunspot number and 10.7 cm solar flux. It is suggested that quasi-biennial oscillations observed in the geomagnetic field, cosmic rays, stratospheric zonal wind and temperature, total ozone, and other meteorological parameters could be produced by a common cause on the sun.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Nov. 197
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  • 88
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    Dependence of the charge exchange lifetimes on mirror latitude (1976)
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    Publication Date: 2011-08-17
    Description: The dependence of the charge exchange lifetimes on the mirror latitude for ions mirroring off the geomagnetic equator has been re-computed using improved hydrogen distribution models. The Chamberlain model, with the input parameters determined by recent satellite observations, has been used to define the spatial distribution of the neutral hydrogen environment through which the ring current ions traverse. The resultant dependence of the charge exchange lifetime, tau, on mirror latitude, lambda-m, is best fit by the approximation tau-m = tau-e cos 3.5 lambda-m, where tau-e is the charge exchange lifetime for the equatorial particles.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Nov. 197
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  • 89
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    Solar activity geomagnetic field and terrestrial weather (1976)
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    Publication Date: 2011-08-17
    Description: Spectral analysis is used as an independent test of the reported association between interplanetary-magnetic-field structure and terrestrial weather. Spectra of the Ap geomagnetic activity index and the vorticity area index for the years from 1964 to 1970 are examined for common features that may be associated with solar-related phenomena, specifically for peaks in the power spectra of both time series with periods near 27.1 days. The spectra are compared in three ways, and the largest peak with the smallest probability estimate is found to occur at a period of 27.49 days. This result is considered to be statistically significant at the 98% level. It is concluded that the period derived from the Ap spectrum is related to solar rotation and that the analysis provides supporting evidence for a connection between the vorticity area index and solar activity.
    Keywords: GEOPHYSICS
    Type: Nature; 264; Nov. 18
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  • 90
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    Discrepancy between electron heating and cooling rates derived from Atmosphere Explorer-C measurements (1976)
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    Publication Date: 2011-08-17
    Description: The present theory of electron temperature in the daytime mid-latitude ionosphere is tested by using Atmosphere Explorer-C measurements. In the region below 300 km, where a balance is expected between electron heating by photoelectron impact and electron cooling to ions and neutrals, we find an imbalance in which the cooling rate is consistently higher than the heating rate. The shapes of the altitude profiles also differ substantially. The cooling rate has a sharp peak at about 220 km, while the heating rate exhibits a broad peak about 30 km lower. Improved agreement is achieved at higher altitudes by using an oxygen fine structure loss rate smaller by a factor of 2, based on more recent collision strength calculations. Although this improves the overall agreement of the heating and cooling rates, the shape discrepancy remains, and the new cooling rate falls consistently below the heating rate below 200 km.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Nov. 1
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  • 91
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    Chinese records on the correlation of heliocentric planetary alignments and earthquake activities (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: GEOPHYSICS
    Type: Icarus; 29; Nov. 197
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  • 92
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    New fine structure cooling rate (1976)
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    Publication Date: 2011-08-16
    Description: One of the dominant electron cooling processes in the ionosphere is caused by electron impact induced fine structure transitions among the ground state levels of atomic oxygen. This fine structure cooling rate is based on theoretical cross sections. Recent advances in the numerical cross section determinations to include polarization effects and more accurate representations of the atomic target result in new lower values. These cross sections are employed in this paper to derive a new fine structure cooling rate which is between 40% and 60% of the currently used rate. A new generalized formula is presented for the cooling rate (from which the fine structure cooling rate is derived), valid for arbitrary mass and temperature difference of the colliding particles and arbitrary inelastic energy difference.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Sept
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  • 93
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    A mid-latitude ozone model for the 1976 U.S. standard atmosphere (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A mid-latitude northern hemisphere model of the daytime ozone distribution in the troposphere, stratosphere, and lower mesosphere has been constructed. Data from rocket soundings in the latitude range of 45 deg N + or - 15 deg N, results of balloon soundings at latitudes from 41 to 47 deg N, and latitude gradients from satellite ozone observations have been combined to produce estimates of the annual mean ozone concentration and its variability at heights up to 74 km for an effective latitude of 45 deg N. This model is a revision for heights above 26 km of the tentative mid-latitude ozone model, included in the U.S. Standard Atmosphere Supplements, 1966, and has been adopted for use in the U.S. Standard Atmosphere, 1976.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Aug. 20
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  • 94
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    Injection boundary dynamics during a geomagnetic storm (1976)
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    Publication Date: 2011-08-16
    Description: A series of proton and electron injections were observed by Explorer 45 associated with several substorms during the main phase of the Feb. 24, 1972 geomagnetic storm. The 1- to 290-keV protons and 1- to 560-keV electrons were observed in the evening quadrant up to L of about 5.2. A model distorted dipole magnetic field and McIlwain's E3 convection electric field were used to backtrack the energy-dispersed electron and proton fluxes to their source at the time of injection. The source turns out to be a region extending over several earth radii outside an injection boundary. In the night magnetosphere, the inferred injection boundary is displaced inward with each successive substorm. The energy dispersion plot of the particles injected during orbit 314 indicates that as the energy of the observed particles decreases there is a smooth transition to the position of the plasmapause. This suggests that for that substorm the injection boundary and the plasmapause were one and the same. The proton 'noses' reported by Smith and Hoffman (1974) are discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Aug. 1
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  • 95
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    Comparison of satellite self-contamination experiments and scattering return flux calculations (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Gaseous emissions from a spacecraft modify the orbital environment and degrade the observations of distant radiation sources. These emissions also provide contamination fluxes induced by self-scattering and scattering with ambient particles. Experiments were carried out on the orbiting Atmosphere Explorer D satellite (AE-D) to verify the calculated return fluxes of a neon source. Known rates of neon were emitted in the direction of the velocity vector on command from the MRMU (molecular return measurement unit). At 250 km the neutral mass spectrometer indicated a total neon return flux of 0.0246 times the emitted flux. The calculated fraction was 0.0123, including 0.00914 for the ambient scatter and 0.00354 for the altitude-independent self-scatter. The pressure gages indicated pressures less than 7 microtorr at altitudes from 161 to 210 km. The maximum pressure for the 161-km orbit was calculated as 0.74 microtorr.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 83; Jan. 1
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  • 96
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    Comparison of the San Marco 3 Nace neutral composition data with the extrapolated Ogo 6 empirical model (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An investigation is conducted concerning the feasibility to extrapolate the data of the Ogo 6 empirical composition model to altitudes which are lower than 450 km. Extrapolated Ogo 6 model densities are, therefore, compared with data obtained in the Neutral Atmospheric Composition Experiment (Nace) carried out during the time from April to November 1971. The results of the investigation support the conclusions of an earlier comparison of Ogo 6 and Nace data conducted by Newton et al. (1973).
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Mar. 1
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  • 97
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    Behavior of the sodium and hydroxyl nighttime emissions during a stratospheric warming (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The behavior of the sodium and hydroxyl nighttime emissions during a stratospheric warming has been studied principally by use of data from the airglow photometers on the OGO 4 satellite. During the late stages of a major warming, both emissions increased appreciably, with the sodium emission returning to normal values prior to the decrease in the hydroxyl emission. The emission behaviors are attributed to temperature and density variations from 70 to 94 km, and a one-dimensional hydrostatic model for that altitude range is used to calculate the effects on the emissions and on the mesospheric ozone densities. These results support the existence of a warming in the upper part of the mesosphere that is correlated with a major stratospheric warming.
    Keywords: GEOPHYSICS
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  • 98
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    Measurements of atmospheric ozone made from a GASP-equipped 747 airliner Mid-March, 1975 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: This paper presents data on the ozone mixing ratio, static air temperature, wind speed, and wind direction obtained at altitudes from 8 to 12 km during several flights of a commercial airliner equipped with a fully automated air-sampling system developed for the NASA Global Atmospheric Sampling Program (GASP). The objectives of GASP are reviewed, and the data-gathering techniques are described. Two data sets are discussed which illustrate variations of the upper-tropospheric and lower-stratospheric ozone mixing ratios as a function of geographical location and aircraft altitude. Good agreement is found between the GASP data and the tropopause height obtained from National Meteorological Center gridded data.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 3; Feb. 197
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  • 99
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    Contributions to the National Geodetic Satellite Program by Goddard Space Flight Center (1976)
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    Publication Date: 2011-08-16
    Description: The major scientific contributions of Goddard Space Flight Center to the National Geodetic Satellite Program between 1965 and 1973 are presented and discussed. The primary results described are the determination of the earth's gravitational field from satellite tracking and surface gravimeter data to an accuracy of about 4 mGal for wavelengths of about 1000 km and larger; the construction of a detailed geoid suitable for geodetic, tectonic, and altimetry data analysis accurate to about 2 m over continents and to 2-5 m over the northeast Pacific and Atlantic oceans; and the positioning of globally distributed tracking stations to an accuracy of 5-10 m for the interconnecting of local geodetic datums. In addition, work on the observation of the earth and ocean tidal perturbations of satellites is discussed and reviewed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 81; Feb. 10
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  • 100
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    Observations of magnetospheric ionization enhancements using upper hybrid resonance noise band data from the RAE 1 satellite (1976)
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    Publication Date: 2011-08-16
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research vol. 81; Jan. 1
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