A Study of Localized Momentum Forcing in the Thermospheres
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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The response of the neutral atmosphere to momentum forcing at F-region heights about 400 km is investigated. The appropriate form of the momentum equations as it pertains to the observed local acceleration of the wind at a specified location is developed. Experiments were performed using data generated by a thermospheric general circulation model TGCM. The acceleration of the neutral wind at several locations and times were compared with the sum of the forcing terms of the momentum equation. The appropriate forms of the equation for stationary as well as moving observers were used, the latter being applied to satellites orbiting at thermospheric altitudes. The momentum equation was analyzed to determine which forces could be calculated solely from the data typically gathered by the Dynamics Explorer DE-2 satellite Both synthesized and actual satellite data were used in the various experiments. Techniques and software were developed to assist in the data handling and subsequent analysis. The results ranged from excellent agreement between the observed acceleration and total forcing for the case of a fixed observer when archived TGCM data was used, to virtually no correlation between measured momentum forcing and observed acceleration in the case of the satellite-borne measurements. It was found that the best results were obtained when the effect of ion drag on the neutral wind was at a minimum. This occurred during the evening hours when ion densities were lowest and at low latitudes away from polar electric fields. A detailed analysis on measurement uncertainty and its potential effect on the results is also presented.
- Atmospheric Physics