The Cluster set of spacecraft in combination with other operating satellites are well-suited for the study of plasma sheet thinning and expansion associated with magnetospheric substorm dynamics in the Earth’s magnetotail. The Cluster orbital apogee of r=19 RE often places the spacecraft set in a very good location to be close to the substorm neutral line (reconnection) position. Starting with energetic particle data from the Cluster spacecraft, we have identified numerous clear substorm events in the last decade of tail passage seasons. We have also examined corresponding information in POLAR, geostationary orbit, and solar wind spacecraft data sets. We find that thinning/expansion sequences are observable quite broadly over large radial and azimuthal distances in most events. However, details of particle burst phenomena differ markedly with radial distance. We use global MHD magnetospheric modeling with realistic solar wind driving conditions to study substorm expansion phase features. We also devote special attention to the study of the substorm recovery phase: This is an aspect that has been much neglected both observationally and theoretically. In this presentation I will focus on the implications of these new observations and model results for substorm models.