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Larsen & Walterscheid 1995
Larsen, M.F. and Walterscheid, R.L. (1995). Modified geostrophy in the thermosphere. Journal of Geophysical Research 100: doi: 10.1029/95JA00137. issn: 0148-0227.

A number of modeling studies, as well as analyses of satellite data, have shown that the neutral winds in the F region are characterized by an approximate balance between the pressure gradient, the Coriolis and curvature acceleration, and viscous and ion drag in the direction perpendicular to the electric field momentum source. The ion drag in the F region is associated with the Pedersen conductivity terms and is often called the Pedersen drag. The dynamics associated with such a balanced flow are reasonably well understood. In the lower thermosphere, the balance of forces becomes more complicated and leads to interesting new flow configurations as the effect of the Hall drag becomes increasingly important. Specifically, the Hall drag coefficient has the effect of decreasing the magnitude of the effective Coriolis parameter, since the Coriolis parameter always appears in combination with the Hall drag term. We examine the balance of forces in the lower E region across the range of heights where the Hall drag terms dominate at the lower altitudes and the Pedersen drag terms dominate at the higher altitudes. The balanced flow solutions predict distinctly different flows in the regions in which the plasma accelerates the neutrals and in the regions in which the plasma induces a drag. The analogs of the thermal wind equations are also presented. The results show that the flow in the lower E region is enhanced and will be in a direction that is antiparallel to the F region plasma flow direction and that the largest shears should occur on the bottomside of the wind maximum. Large convergent/divergent flows are expected on the equatorward side of the auroral oval, and the maximum convergence/divergence is expected near a height of ~110--120 km. ¿ American Geophysical Union 1995

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Abstract

Keywords
Ionosphere, Ionosphere/atmosphere interactions, Meteorology and Atmospheric Dynamics, Thermospheric dynamics, Ionosphere, Auroral ionosphere
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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