The first GEM (Geospace Environment Modelling) theory- observing campaign addresses problems of the magnetopause, boundary layers, and their signatures in the cusp of the ionosphere. Participants in the observing workshop held last October 1989 at the University of Maryland determined that the first task of the campaign should be the confident identification of cusp signatures in ground-based and airborne data by intercalibrating with spacecraft particle data on direct overflights of the ground-based and airborne facilities. The relatively easily recognized cusp particle signatures from the spacecraft instruments would serve as a Rosetta stone for deciphering signatures below. To this end, a pilot data- gathering program took place in the vicinity of the dark cusp on January 16, 1990, and many groups are gathering archival data for intercalibration. This grant is for a workshop to bring these data together for analysis and theoretical interpretation.
