Joint Cluster/Ground-Based Studies in the First 20 Years of the Cluster Mission

Ground-based facilities make an important contribution to our understanding of the magnetospheric system. Coordination with ground-based facilities has been embedded within the Cluster mission since before launch, and this has given rise to a large number of studies which have exploited data from both Cluster and one or more of the diverse range of ground-based instrumentation that have been available during the mission timespan. In this paper, we review the advances that have been made to our understanding of the magnetosphere-ionosphere system, in which insight has been enhanced by combining ground-based observations with observations from Cluster. Topics covered span from the bow shock to the magnetotail and down to the aurora.