The coupling of the ionosphere to the magnetosphere is a critical component to the understanding of the dynamics of energy flow in these regions. This project will address the coupling that results from the interaction of the polar wind with the field-aligned electric potential drops that produce the so-called "inverted V" signature in ion energy spectrograms. The coupling process takes place on all spatial scales down to the ion gyroradius and this program will address the interaction mechanisms at all these scales. The program will determine the relative importance of a variety of phenomena, including the mirror force, convection, conduction, diffusion, and wave-particle interactions. This work will build on the transport model developed by the PI under prior NSF support.