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  • 1
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    Scattering by nonspherical particles of size comparable to wavelength - A new semi-empirical theory and its application to tropospheric aerosols (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A semiempirical theory is developed which is based on simple physical principles and comparisons with laboratory measurements. The ultimate utility of this approach rests on its ability to successfully reproduce the observed single-scattering phase function for a wide variety of particle shapes, sizes and refractive indices. This approximate theory is developed for evaluating the interaction of randomly oriented, nonspherical particles with the total intensity component of electromagnetic radiation. Mie theory is used when the particle size parameter x (ratio of particle circumference to wavelength) is less than some upper bound x sub zero (about 5). For x greater than x sub zero, the interaction is divided into three components: diffraction, external reflection and transmission. The application of the theory is illustrated by considering the influence of the shape of tropospheric aerosols on their contribution to the earth's global albedo.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences; 37; Apr. 198
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  • 2
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    The use of hydroxyacids as geochemical indicators (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The distributions of hydroxyacids in a variety of recent and ancient sediments have been determined by gas chromatography-mass spectrometry. A lacustrine sediment (Rostherne Mere, U.K.) and two marine situations (Cariaco Trench, Black Sea) were analyzed as examples of recent depositional environments. Beta-hydroxyacids occurred in all of the recent sediments, consistent with their presumed microbial origin, whereas di- and trihydroxyacids were present in the sediments with a significant higher plant input (Black Sea and Rostherne Mere sediments). The two ancient (Eocene) sediments examined, viz, the Greene River (U.S.) and Messel (Germany) oil shales, contained only trace amounts of hydroxyacids. These results provide evidence that hydroxyacids are in general not well preserved over geological time.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 47; April 19
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  • 3
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    A seasonal change in the effect of field-aligned currents at synchronous orbit (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The expected signature of substorm field-aligned currents is described for synchronous satellites near 10 deg magnetic latitude. The main effect is a positive D perturbation premidnight and a negative D perturbation postmidnight. This behavior is illustrated for two substorms near the fall equinox. A second pair of substorms taken from winter solstice do not show the expected behavior. The absence of this effect in winter observations is verified statistically by superposed epoch analysis. A simple explanation of this behavior based on the geometry of the plane of magnetic symmetry is presented. During disturbed times at winter solstice a synchronous satellite nominally at 10 deg magnetic latitude is effectively at the magnetic equator. This distortion of the magnetic equator must be considered in future models of the disturbed magnetospheric magnetic field.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 85; Dec. 1
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  • 4
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    Global simulations of the three-dimensional magnetosphere (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Global three-dimensional computer simulations of the magnetosphere using a particle MHD code, reproduce the steady-state Dungey magnetospheric topology in three dimensions. The formation of a compression zone downstream of the tail neutral line that is probably bounded by wake shocks is observed. This compression zone changes its cross-section with distance downstream.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 8; Mar. 198
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  • 5
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    DE 1 observations of type 1 counterstreaming electrons and field-aligned currents (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Dynamics Explorer 1 satellite observations of plasma and magnetic fields during type one counterstreaming electron events are presented. Counterstreaming electrons are observed at high altitudes in the region of field-aligned current. The total current density computed from the plasma data in the 18-10,000 eV energy range is generally about 1-2 micro-A/sq m. For the downward current, low-energy electrons contribute more than 40 percent of the total plasma current density integrated above 18 eV. For the upward current, such electrons contribute less than 50 percent of that current density. Electron beams in the field-aligned direction are occasionally detected. The pitch angle distributions of counterstreaming electrons are generally enhanced at both small and large pitch angles. STARE simultaneous observations for one DE 1 pass indicated that the field-aligned current was closed through Pedersen currents in the ionosphere. The directions of the ionospheric current systems are consistent with the DE 1 observations at high altitudes.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 8907-891
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  • 6
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    A simulation study of cold electron heating by loss cone instabilities (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Results are presented of a computer simulation study of electron cyclotron harmonic waves; an electrostatic finite size particle simulation code is used. The initial electron velocity distribution function is modeled as a hot ring perpendicular to the ambient magnetic field and a cold Maxwellian component. Nonlinear cyclotron resonance is found to be the saturation mechanism of the unstable waves and the heating mechanism of the cold electrons. The results can be related to certain ionospheric phenomena.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 7; Nov. 198
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  • 7
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    Plasma injection and transport in the mid-altitude polar cusp (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: DE-1 hot plasma observations in the mid-altitude polar cusp have shown evidence of a significant velocity filtering phenomenon which is consistent with a latitudinally narrow region of plasma injection located at a geocentric distance of about eight earth radii (in a dipole approximation). Plasma convection from the injection region into the polar cap results in a V-shaped log E vs. observed pitch angle relation at geocentric distances near 4 earth radii. This velocity filtering effect allows the measurement of much smaller flow velocities (about 10 km/sec) than have heretofore been possible with hot plasma measurements. The flows thus determined are consistent with ionospheric flows measured nearly simultaneously by the DE-2 spacecraft, although the magnitudes of the higher altitude flows are higher by a factor of 2 or more than an approximately r to the 3/2 power dipole-field mapping would predict.
    Keywords: GEOPHYSICS
    Type: AD-A121705 , AFGL-TR-82-0336 , Geophysical Research Letters; 9; Sept
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  • 8
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    The seismotectonics of plate boundaries (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.
    Keywords: GEOPHYSICS
    Type: NASA-CR-165050
    Format: application/pdf
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  • 9
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    Calculated stormtime variations in plasmaspheric thermal ion composition (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Model calculations describing stormtime variations in the earth's dayside plasmasphere are used to examine variations in ion composition. The model storm is initiated by high-latitude thermospheric heating that generates meridional winds that carry neutral species, momentum, and energy equatorward. The thermosphere acts on the plasmasphere through collisional transfer of momentum and through chemical reactions between neutral species and ions. Over latitudes near the region of thermospheric heating, the thermosphere-plasmasphere coupling processes cause enhancement in the density of oxygen ions while protons are being lost. Meanwhile, densities of oxygen ions and protons near the equator are increasing together, almost in phase. The largest enhancements in ion density develop at latitudes near 45 deg invariant for both oxygen and hydrogen.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 10233-10
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  • 10
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    A magnetospheric signature of some F layer positive storms (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Calculations of electron density distributions in the global thermosphere-ionosphere system perturbed by high-latitude thermospheric heating are presented which indicate a link between the heating and magnetospheric plasma disturbances near the equator. The calculations were made using a self-consistent model of the global sunlit thermosphere-ionosphere system describing the evolution of equatorial plasma disturbances. The heat input is found to cause electron density enhancements that propagate along magnetic field lines from the F2 maximum over mid-latitudes to the equator in the magnetosphere and which correspond to the positive phase of an F layer storm. The positive phase is shown to be generated by the induction of equatorward winds that raise the mid-latitude F layer through momentum transfer from neutral atoms to ionospheric ions, which ions pull electrons with them. Model results are used to identify plasma signatures of equatorward winds and an intensified magnetospheric electric field in Explorer 45 and Arial 4 measurements taken during the positive phase of an F layer storm.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; May 1
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