Structuring of space plasma

Space plasma is very inhomogeneous and intrinsically subjected to fragmentation as indicated by many plasma and field structures repeatedly observed in the Earth's environment. For example, velocity dispersed ion structures with stratification of the ions energy as well as recurrent time of flight dispersed ion structures signal the local "fragmentation" of the magnetotail. This fragmentation is also revealed by the formation of closed structures like plasmoids ejected anti-earthward and of elongated thin structures, like beamlets ejecting matter towards the Earth. As evidenced by many satellite measurements, bursty bulk flows transport plasma and magnetic field more efficiently than steaty state convection. At the interface between the solar and planetary plasma, flux transfer events could be the main mechanism allowing the solar plasma to enter inside the magnetosphere, ultimately forming the polar cusp. All these entities represent structures in space, time and often in velocity space as well. To catch their spatio-temporal patterns we need advanced, high resolution multi-point measurements. In this respect, the analysis of Cluster results is timely and important for future space plasma physics like THEMIS, MMS and for future satellite constellations. Taking advantage of the Cluster data and considering the various scales involved in plasma fragmentation and their coupling, we discuss what could be the necessary measurements in order to made further progresses.