The phenomenon of plasmasphere refilling, and general considerations of plasmasphere structure and plasmasphere-ionosphere coupling, have received increased attention in recent years in terms of both observational considerations and modeling investigations. New ideas arising from both observations and modeling efforts are revealing the refilling region to be rich in intriguing physical processes, including hot-cold plasma interactions through wave-particle effects and Coulomb collisions, electrostatic shocks, and differences in light and heavy ion behavior during refilling. ''Global'' observational and modeling studies of the plasmasphere structure are in the process of demonstrating the complex manner in which refilling and the spatial and temporal variations of convection interplay to produce complex structure in the plasmasphere; these studies are particularly timely as they could be extremely helpful or interpreting results from proposed imaging of plasmaspheric He+. This review will serve to highlight the observational and theoretical/modeling progress during the past few years as well as to introduce and place in context the particular contributions contained in this special section. ¿ American Geophysical Union 1992