This grant is to continue a coordinated program of theoretical modeling and analysis of existing satellite data directed toward an improved understanding of the interaction of the solar wind with the terrestrial magnetosphere-ionosphere system. Key elements of the work include: (A) quantitative time-dependent modeling of the open magnetospheric field configuration and the resultant mapping of the solar-wind electric field to the polar caps; (B) empirical study of polar- cap convection patterns and of the polar-cap potential drop under time-variable solar-wind/IMF conditions; and (C) empirical study of thermal and suprathermal electron populations above auroral acceleration regions and their mapping to the magnetotail plasma sheet. The modeling efforts combine the flexibility and physical clarity of analytical formulations with the computational power of modern supercomputers. The data analysis efforts combine multiple spacecraft datasets to address specific questions posed by theory. The close coordination of modeling and data-analysis activities has a synergistic effect on understanding the complex solar-terrestrial system.
