HR: 13:40h
AN: SA32A-01 INVITED     [PDF]
TI: Some Aspects of the Momentum Balance in Thermospheric Dynamics
AU: * Fuller-Rowell, T
EM: tim.fuller-rowell@noaa.gov
AF: NOAA Space Environment Center and CIRES University of Colorado, 325 Broadway, Boulder, CO 80305 United States
AB: In the absence of drag, zonally averaged meridional pressure gradients drive purely zonal winds. However, the ions present in a weakly ionized thermosphere are constrained by electromagnetic forces and introduce a drag on the fluid. Zonal winds are slowed, and a global meridional circulation develops that introduces neutral composition changes and a feedback on the ionosphere. At high latitudes, where the magnetospheric convection electric fields force plasma to high velocities, collisions with the neutral atmosphere imparts a momentum source driving winds of many hundreds of meters per second. In addition, inertial forces introduce large asymmetries in the wind magnitudes expected in the dawn and dusk sector of the auroral oval. Sudden changes in high latitude forcing drive global-scale gravity wave surges. These surges propagate towards the equator, transmit new pressure fields, and impact the global wind field. At low latitudes, the Coriolis force tends to zero, leading to possibility of unforced zonal winds. Equatorial electrodynamics can move plasma and produce regions where ion drag is virtually zero, allowing large zonal winds to emerge.
DE: 0358 Thermosphere--energy deposition
DE: 2415 Equatorial ionosphere
DE: 2427 Ionosphere/atmosphere interactions (0335)
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting