The interactions between the solar wind and the Earth's magnetosphere are responsible for the complex dissipative processes which control the dynamics of the near earth environment. The study of these processes is the basic theme of solar-terrestrial research. The plasma sheet, its boundary layer, and the high latitude auroral region are of central importance in the understanding of these processes. The existence of the plasma sheet in the geomagnetic tail and the dawn-to-dusk electric field across the tail implies there is a significant energization of the particles carrying the crosstail current. This energization of particles in the tail represents ~2% of the total energy carried by the solar wind over an area equal to the cross section of the dayside magnetosphere, and thus this energization is an important, and perhaps the dominant means by which solar wind energy is transferred to magnetospheric particles. Current sheet acceleration of ions is responsible for the unstable ion beams found in the plasma sheet boundary layer (PSBL). The resulting motion of both ion and electron particle populations are the likely cause not only of the formation of the isotropic plasma sheet, but of the high latitude potential structure responsible for discrete arcs in the auroral region. Discrete auroral arcs are associated with regions of upward current carried by downward precipitating electrons which have been accelerated through a field-aligned potential difference of 10,000votts. Cold ionospheric ions are accelerated upward by the same potential drop. This grant is composed of three projects: A) magnetotail particle dynamics, B) broadband turbulence and particle diffusion in the plasma sheet, and C) instabilities in the auroral acceleration region. Both the magnetotail and the auroral region are dynamically active and of central importance in the mechanics of the magnetosphere. They are also intimately coupled to each other. Better understanding of the current and particle self- consistencies, acceleration mechanisms, and particle diffusion in the magnetotail and interactions of beams in the auroral zone will lead to an improved global picture of the dynamics of the magnetosphere.
