HR: 16:15h
AN: SA24A-02    [Abstracts]
TI: Active Roles of the Ionosphere in the Electrodynamic M-I Coupling
AU: * Zhu, L
EM: zhu@cc.usu.edu
AF: Center for Atmospheric and Space Sciences, Utah State University, 4405 Old Main Hill, Logan, UT 84322-4405 United States
AU: Schunk, R W
EM: schunk@cc.usu.edu
AF: Center for Atmospheric and Space Sciences, Utah State University, 4405 Old Main Hill, Logan, UT 84322-4405 United States
AU: Sojka, J J
EM: fasoka@sojka.cass.usu.edu
AF: Center for Atmospheric and Space Sciences, Utah State University, 4405 Old Main Hill, Logan, UT 84322-4405 United States
AB: Magnetosphere-ionosphere (M-I) coupling is a key element in the Sun-Earth connection and is of fundamental importance to understanding the basic properties of the ionosphere and magnetosphere and how the solar variations affect the near-Earth space environment. One of the most important couplings between the magnetosphere and the ionosphere is the electrodynamic coupling represented by the convection electric field, field-aligned currents, and conductivity. In the recent years, it has been increasingly realized that in the electrodynamics of the M-I coupling the ionosphere is not a passive medium with the magnetosphere acting as a driver, instead, the ionosphere can play very active roles. These active ionospheric roles not only exist in the M-I electrodynamic processes initiated in the ionosphere (terminator effect, solar eclipse, etc.), but also have been manifested in the M-I processes initiated or driven by the magnetosphere, for example, substorms. In this presentation, we will use quantitative results from a time-dependent electrodynamic model of M-I coupling to demonstrate and discuss various aspects of the active ionospheric roles in the electrodynamic M-I coupling, including 1) how the ionospheric conditions determine the loading of the magnetospheric convection on the ionosphere and how these convection patterns are distorted at the ionospheric altitude; 2) under what conditions, the ionosphere can generate its own field-aligned currents and small-scale electric field structures that are not in the magnetospheric driver; 3) how the ionosphere launches its own Alfven waves, thus modifying the ionospheric convection field and sending the information of the ionospheric dynamic changes back to magnetosphere; 4) properties of the M-I processes without the magnetospheric driver. It is clear from our modeling results that the ionosphere plays important role in generating small-scale plasma and electrodynamic structures and these small-scale structures are essential for us to understand the physics of the M-I system and to specify the near-Earth space weather.
DE: 2411 Electric fields (2712)
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2435 Ionospheric disturbances
DE: 2447 Modeling and forecasting
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005