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  • Other Sources  (8)
  • 1980-1984  (8)
  • 1975-1979
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  • 1
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    Observations of the dynamics of the polar thermosphere (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The dynamics of the polar thermosphere are examined by using observations made from the Dynamics Explorer 2 satellite. The results used in this study were obtained primarily from the Fabry-Perot interferometer (FPI) and the wind and temperature spectrometer (WATS) during the time period from September 1981 through January 1982. Two primary geophysical conditions were examined: these were the southern summer and the northern winter polar regions. The results support the conclusion that above 60 degrees of latitude the neutral winds are strongly controlled by ion/neutral frictional momentum transfer resulting from magnetospheric convection. This implies that the natural coordinate system within which to display the neutral winds in the high polar thermosphere is magnetic. The collected observations of this study were used to assess the validity of two of the large thermospheric general circulation models. The result of this assessment was that the models reasonably represent the vector winds at high altitudes but do not, at present, accurately simulate the thermodynamics of that regime.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 5597-561
    Format: text
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  • 2
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    Midlatitude measurements of the ionospheric electric field during the ALADDIN programme (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Three measurements of ionospheric electric field were made during the 24-h ALADDIN rocket program at Wallops Island on June 29-30, 1974. The first of these used a double probe instrument, flown at 1500 Local Solar Time, and the second and third measurements were made by barium cloud releases at evening and morning twilight. These three electric field vectors have been compared with the predictions of a number of models of electric field due to the dynamo effects of various atmospheric tides, and also of a possible magnetospheric origin. On the assumption that the measurements were made at a location equatorward of the afternoon convergence and poleward of the morning divergence in the electric field patterns related to the Sq current system, Stening's (1973) model of the diurnal variation of the electric field induced by the (1, -2) tidal model at the time of the summer solstice correctly predicts the directions of the observed electric field. Forbes and Lindzen's (1976, 1977) model, incorporating the three major propagating tidal modes as well as the evanescent (1, -2) mode, also bears an acceptable relationship to the ALADDIN electric field directions. The ALADDIN E-field magnitudes are comparable with those obtained by ground-based observations from Millstone Hill and from Saint Santin but are about half of Stening's model values, and three times those of Forbes and Lindzen. Saint Santin E-field directions, at the same latitude but 75 deg difference in longitude, are distinctly different from ALADDIN, implying that longitudinal differences are significant.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 42; June 198
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  • 3
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    A comparison of wind observations of the upper thermosphere from the Dynamics Explorer satellite with the predictions of a global time-dependent model (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Experimental and theoretical investigations of high-latitude circulation in the upper thermosphere are reported. Vector-wind plots constructed by combining remotely sensed meridional-wind and in situ zonal-wind data obtained during four south-polar and three north-polar passes of the NASA Dynamics Explorer satellite in October and December, 1981, are presented and analyzed, taking the geomagnetic activity level and local solar time into account. The results are then compared with the predictions of 3D time-dependent global models of thermospheric neutral winds (Fuller-Rowell and Rees, 1980, 1981, 1983) adjusted to account for both solar-UV/EUV heating and ionization effects and quiet (Kp from 1 to 2) or moderately disturbed (Kp from 3 to 4) geomagnetic conditions (models Q and MD). An MD model incorporating a self-consistent description of the high-latitude ionosphere and a Q model excluding high-latitude effects are found to give the most accurate predictions for the respective geomagnetic conditions.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science (ISSN 0032-0633); 31; 1299-131
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  • 4
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    Wind structure and small-scale wind variability in the stratosphere and mesosphere during the November 1980 Energy Budget Campaign (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Rocket observations made from two sites in northern Scandinavia between November 6 and December 1, 1980, as part of the Energy Budget Campaign are discussed. It was found that significant vertical and temporal changes in the wind structure were present and that they coincided with different geomagnetic conditions, that is, quiet and enhanced. Before November 16, the meridional wind component above 60 km was found to be positive (southerly), whereas the magnitude of the zonal wind component increased with altitude. After November 16 the meridional component became negative (northerly), and the magnitude of the zonal wind component was observed to decrease with altitude. Time sections of the perturbations of the zonal wind reveal the presence of vertically propagating waves, suggesting gravity wave activity. The waves are found to increase in wavelength from 3-4 km near 40 km to more than 12 km near 80 km. The observational techniques made use of chaff foil, chemical trails, inflatable spheres, and parachutes.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: (ISSN 0273-1177)
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  • 5
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    Observations of neutral wind profiles between 115- and 175-km altitude in the dayside auroral oval (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Lithium trail neutral wind measurements have been made in the morning dayside auroral oval as a function of altitude. During all four experiments the winds displayed a large altitude shear. In the most extreme case the wind at 135-km altitude was toward the south at 210 m/s, and at 185-km altitude toward the northwest at 170 m/s. A one-dimensional numerical solution to the Navier Stokes equation including an initial steady-state wind profile, viscosity, pressure gradient, Lorenz force and the Coriolis force was made in order to study the effect of auroral processes on the neutral atmosphere. Since electric fields and plasma density were measured, the Lorenz force could be modeled with reasonable accuracy. The pressure gradient was determined in an iterative way as a best fit to the observations. Within the limitations of a one-dimensional model the numerical solution is in reasonable agreement with one of the observations, which is applicable to such a modeling, and indicates that both Lorenz forces and pressure gradients due to auroral processes are required to explain the observation.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 85; June 1
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  • 6
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    The effect of realistic conductivities on the high-latitude neutral thermospheric circulation (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The dynamics of the high latitude thermosphere are dominated by the ion circulation pattern driven by magnetospheric convection. The reaction of the neutral thermosphere is influenced by both the magnitude of the ion convection velocity and by the conductivity of the thermosphere. Using a three-dimensional, time-dependent, thermospheric, neutral model together with different ionospheric models, the effect of changes in conductivity can be assessed. The ion density is described by two models: the first is the empirical model of Chiu (1975) appropriate for very quiet geomagnetic conditions, and the second is a modified version of the theoretical model of Quegan et al. (1982). The differences in the neutral circulation resulting from the use of these two ionospheric models emphasizes the need for realistic high latitude conductivities when attempting to model average or disturbed geomagnetic conditions, and a requirement that models should couple realistically the ionosphere and the neutral thermosphere. An attempt is made to qualitatively interpret some of the features of the neutral circulation produced at high latitudes by magnetospheric processes.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science (ISSN 0032-0633); 32; 469-480
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  • 7
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    Stable and rugged etalon for the Dynamics Explorer Fabry-Perot interferometer. II - Performance (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The etalon is shown to remain stable to less than 5-m/sec equivalent wind over one orbit and less than 100 m/sec over several months in orbit. The thermal stability considerations for the highly stable etalon are discussed, including the passive thermal control used in flight. The various physical processes which give rise to drifts in the peak transmission wavelength are quantified, and the kinematic mount used to isolate the etalon from large incremental forces caused by changes in the thermal environment is presented. The performance of the etalon in its flight configuration is evaluated.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Applied Optics; 21; Nov. 1
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  • 8
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    A theoretical study of the distribution of ionization in the high-latitude ionosphere and the plasmasphere - First results on the mid-latitude trough and the light-ion trough (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics; 44; July 198
    Format: text
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