Abstract 9423489 Lyons This is a project to investigate how energy from the solar wind enters Earth's magnetosphere. The rate of energy transfer is controlled by the electric field along the separatrix, which is the boundary between open and closed magnetic field lines at the surface of the magnetosphere. For this study, ground-based observations will be used to measure the rate of reconnection of magnetic field lines across the separatrix. Both the motion of the separatrix and the flow of plasma across it must be measured simultaneously. The investigators will measure these quantities using radar and optical techniques with a time resolution sufficient to resolve changes associated with the growth and expansion phases of auroral substorms. The results will be used to test models of plasma convection in the magnetosphere and to evaluate the accuracy of reconnection theories. The variation in reconnection rate associated with auroral substorms and dayside transient effects will also be studied. ***
