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  • 1
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    Inference of high-latitude ionization and conductivity from AE-C measurements of auroral electron fluxes (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Electron fluxes in the kilovolt energy range measured by the AE-C satellite have been used to infer the latitudinal distribution of ionization at high latitudes in the altitude range 90 to 200 km. These distributions are compared with simultaneous measurements of electron density by the Chatanika incoherent scatter radar. The study was based on more than 120 electron density profiles obtained on three different nights at magnetic local times between 0200 and 0400. The calculated distributions agree very well with the altitude and latitude distributions measured by the radar. The only obvious difference was the presence in the radar data of additional ionization produced by solar illumination. A comparison was also conducted of the height-integrated electrical conductivities computed from the measured profiles and those inferred from the satellite measurements. For Hall and Pedersen conductances greater than 5 mhos, the agreement is within 25 percent. The data were also used to deduce the altitude profile of the effective recombination coefficient. This profile agrees well with the results of previous studies.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 7505-751
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  • 2
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    Radar and photometric measurements of an intense type A red aurora (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: On the evening of March 5, 1981, an intense, type A red aurora appeared over southern Alaska. Radar and photometric measurements were made of the aurora from the Chatanika radar site. The line of sight intensity of the 630.0-nm emissions exceeded 150 kR and was accompanied by enhanced emissions at 486.1 and 427.8 nm. The Chatanika radar measured electron densities of 10 to the 6th per cu cm and electron temperatures of 6000 K at an altitude of 400 km and an invariant latitude of 59 deg in association with the aurora. Comparison of optical and radar measurements indicated that the 630.0-nm emissions were produced to a large degree by thermal excitation of O(1D) in the region of high electron temperatures and densities. Model calculations indicate that the observed density and temperature enhancements and the related optical emissions were the results of a relatively short duration (5-10 min) pulse of precipitating, low-energy (about 30 eV) electrons. Whereas conventional stable auroral red arcs are associated with a gradual decrease in ring current energy density during the recovery phase of a magnetic storm, the type A red aurora may be produced by impulsive ring current energy loss during the main phase.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 457-466
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  • 3
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    A comparison of ionospheric conductances and auroral luminosities observed simultaneously with the Chatanika radar and the DE 1 auroral imagers (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Auroral luminosities at vacuum ultraviolet (VUV) wavelengths are combined with simultaneous and coincident ionospheric electron density measurements made by the Chatanika radar to relate ionospheric conductances to optical emissions. The auroral luminosities are obtained along the magnetic meridian through Chatanika with the auroral imaging photometers on the Dynamics Explorer 1 satellite as the radar scans in the magnetic meridian to measure electron density and conductivity as a function of altitude and latitude. The observations are used to determine an empirical relationship between the luminosities measured at VUV wavelengths and the Hall and Pedersen conductances.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 5382-539
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  • 4
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    Plasma and field properties of suprathermal electron bursts (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Plasma and field observations obtained by the Dynamics Explorer satellites during a suprathermal burst event on October 8, 1981, are presented. Because of a correlation between the bursts and low-frequency (less than 1 kHz) electric field wave power, it is suggested that the electrons in the bursts are produced by interaction with the waves. It is found that the waves may be generated in regions of strong upward current and may be propagated perpendicular to the field line to produce accelerated electrons outside the region of wave generation.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 12031-12
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  • 5
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    Stress Measurement by Geometrical Optics (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Fast, simple technique measures stresses in thin films. Sample disk bowed by stress into approximately spherical shape. Reflected image of disk magnified by amount related to curvature and, therefore, stress. Method requires sample substrate, such as cheap microscope cover slide, two mirrors, laser light beam, and screen.
    Keywords: MECHANICS
    Type: LEW-14169 , NASA Tech Briefs (ISSN 0145-319X); 10; 2; P. 114
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  • 6
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    On calculating ionospheric conductances from the flux and energy of precipitating electrons (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Auroral zone conductances can be estimated from the energy flux and average energy of precipitating electrons. Revised expressions are presented that relate height-integrated Hall and Pedersen conductance to the flux and average energy of a Maxwellian. It is shown that the accuracy of this method depends on the minimum and maximum energy within which the distribution is integrated to get the energy flux and average energy. It is also confirmed that the conductances produced by some of the more common auroral spectral distributions are similar to those produced by a Maxwellian with the same average energy and energy flux. The application of these results is demonstrated using precipitating electron measurements made by the Hilat satellite during a pass over Greenland.
    Keywords: GEOPHYSICS
    Type: AD-A180362 , AFGL-TR-87-0152 , Journal of Geophysical Research (ISSN 0148-0227); 92; 2565-256
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