HR: 1340h
AN: SM13B-1327    [Abstracts]
TI: Variations of Ionospheric Convection Electric Field: Under Steady and Non-steady Conditions
AU: * Sun, W
EM: wsun_1939@yahoo.com
AF: 2Geophysical Institute, University of Alaska, 903 Koyukuk Drive, Fairbanks, AK 99775, United States
AU: Zhou, X
EM: Xiaoyan.Zhou@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AB: It is well known that magnetic reconnections at the dayside magnetopause and in the distant magnetotail drive the polar cap convection that has a two-cell pattern in potential. This pattern is twisted westward due to southward turning of electric field in midnight sector during substorm expansion phases. To quantitatively describe the variations of nightside ionospheric electric fields, the natural orthogonal components (NOC) algorithm is applied to separate convection E field and a southward E field that drives the substorm electrojet. It is found that the convection E field is mainly westward in the midnight sector and is stable when there is a lack of substorm expansion phases. A non-steady convection may be enhanced by ~30% of the steady E field magnitude when substorms occur. In addition, the southward E field is found to vary more dramatically than the convection E field from ~5 to 40 mV/m when substorm expansion phase takes place. We will also discuss the interplanetary drivers of the polar cap convection, such as magnetic clouds and other sudden changes in the solar wind.
DE: 2463 Plasma convection (2760)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting