THE MAIN GOAL OF THIS PROPOSAL IS TO QUANTITATIVELY CHARACTERIZE STORM-TIME IONOSPHERIC ELECTRODYNAMICS BASED ON VARIOUS SPACE AND GROUND BASED OBSERVATIONS TOGETHER WITH ADVANCED DATA ASSIMILATION TECHNIQUES AND NUMERICAL SIMULATIONS. THIS INVESTIGATION WILL MAKE EXTENSIVE USE OF DATA FROM BOTH CURRENT AND PAST NASA MISSIONS INCLUDING TIMED IMAGE AND POLAR LEVERAGED BY OTHER SPACE AND GROUND BASED OBSERVATIONS IN ORDER TO OBTAIN THE MOST REALISTIC SPECIFICATION OF GLOBAL IONOSPHERIC ELECTRODYNAMIC FIELDS UNDER DIFFERENT SOLAR WIND AND GEOMAGNETIC CONDITIONS BY APPLYING THE ASSIMILATIVE MAPPING OF IONOSPHERIC ELECTRODYNAMICS (AMIE) PROCEDURE. WE WILL ALSO USE THE THERMOSPHERE-IONOSPHERE- ELECTRODYNAMICS GENERAL CIRCULATION MODEL (TIEGCM) TO DELINEATE THE VARIOUS PHYSICAL PROCESSES AFFECTING THE THERMOSPHERE. NUMERICAL EXPERIMENTS WILL BE CONDUCTED TO DETERMINE HOW THE DIFFERENT SPECIFICATIONS OF IONOSPHERIC ELECTRODYNAMIC FIELDS AFFECT THERMOSPHERIC DYNAMICS GLOBALLY.