Neutral wind vortices in the high-latitude thermosphere.
An investigation into the neutral dynamics of the high-latitude thermosphere has been carried out using measurements obtained from the Dynamics Explorer-2 spacecraft and ground-based Fabry-Perot interferometers located in Greenland, and numerical simulations from the National Center for Atmospheric...
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| Format: | Thesis |
| Language: | English |
| Published: |
1990
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| Online Access: | https://hdl.handle.net/2027.42/128602 http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:9034528 |
| Summary: | An investigation into the neutral dynamics of the high-latitude thermosphere has been carried out using measurements obtained from the Dynamics Explorer-2 spacecraft and ground-based Fabry-Perot interferometers located in Greenland, and numerical simulations from the National Center for Atmospheric Research - Thermosphere/Ionosphere General Circulation Model (NCAR-TIGCM). In this thesis, large-scale mean neutral wind patterns under various geophysical conditions have been determined through extensive analysis of the neutral wind observations made by the DE-2 spacecraft. The mean neutral wind observations demonstrate the existence of coherent, large-scale neutral wind vortices in the high-latitude thermosphere and show that these vortices are persistent features in the mean neutral wind circulation. The mean neutral wind vortices in the high-latitude thermosphere are shown to vary spatially depending on the orientation of the interplanetary magnetic field (IMF) and the level of geomagnetic activity. In this work, the NCAR-TIGCM has been used to provide numerical simulations of the high-latitude neutral circulation corresponding to the geophysical conditions under which the averaged neutral wind patterns from DE-2 observations were organized. The high-latitude neutral wind vortices determined from the DE-2 observations and simulated by the NCAR-TIGCM have been analyzed in detail in this thesis by determining the kinematic properties of the wind fields. This analysis has shown that the dynamics of the high-latitude neutral thermosphere is dominated by rotational motion, imparted primarily through the ion-drag force, rather than by divergent motion, imparted primarily through the pressure gradient force set up by Joule and solar heating. The numerical simulations of the NCAR-TIGCM provide information on the forces which generate the neutral wind forces in the high-latitude thermosphere. The force analysis illustrates that the ion-drag force contributes significantly to the local time rate of change of the ... |
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