James L. Burch.C. Philippe Escoubet Originally published in the journal Space Science Reviews, Volume 145, Nos 1-2, 1-2. DOI: 10. 1007/s11214-009-9532-7 (c) Springer Science+Business Media B. V. 2009 The IMAGE and CLUSTER spacecraft have revolutionized our understanding of the inner magnetosphere and in particular the plasmasphere. Before launch, the plasmasphere was not a prime objective of the CLUSTER mission. In fact, CLUSTER might not have ever observed this region because a few years before the CLUSTER launch (at the beginning of the 1990s), it was proposed to raise the perigee of the...