Motivated by new and abundant datasets obtained in the course of Cluster spacecraft traversals of the Earth's magnetotail current sheets, we propose a multi-aspect study, where we plan to systematize and characterize the wealth of in situ observations. The current sheets are a universal phenomenon in astrophysical, solar system and planetary plasmas where they form at the boundaries between plasmas and/or magnetic fields of different origin. They are principal sites of effective conversion of magnetic energy to kinetic energy even in the absence of Coulomb collisions. Spacecraft experiments provide us with the only possibility for detailed direct in situ study of current sheets in the Earth's magnetosphere, where violent plasma processes occur in the magnetotail current sheet, leading to explosive energy dissipation during substorms and magnetic storms. Little is presently known about the internal structure of this current sheet, its temporal changes and stability, because it is very difficult to study it with data from a single spacecraft. Theory research has mostly addressed the simplest configuration, a so-called Harris current sheet. The situation has changed dramatically with the launch and operation closely-spaced four Cluster spacecraft (2000-2005). The Cluster spacecraft provide a unique opportunity to distinguish between spatial and temporal changes in the measured plasma parameters. Our research is primarily based on Cluster measurements and includes: (1) A systematic experimental study of current sheets profiles and characteristics in the Earth's magnetotail using novel multi-point spacecraft measurements. (2) An extension of collisionless kinetic theory to different types of current sheets (other than one-dimensional Harris sheet), providing the theory basis for the classification of observed current sheets. (3) Investigation of evolution and stability of various types of current sheets and their implications for particle energization and large-scale dynamics in substorms. Integrity to this study is provided by the complementary scientific experience of the teams involved. The project will enable the joint coordinated effort of experimentalists and theorists, Cluster scientists and researchers, having rich experience in analysis of data from Interball, Geotail and other preceding missions. Moreover most of the NIS and INTAS teams involved have a very successful record of previous collaboration, which has resulted in dozens of joint publications. Joint efforts should significantly advance our knowledge of current sheets in high-temperature plasmas, a unique and very important phenomenon.
RH6 6NT Dorking