Plasma Physics Seminar ( Phys 769)

Jonathan Eastwood, GSFC

Cluster Observations of Magnetotail Dynamics: Using Multi-point Observations to Establish Plasma Dynamics

The Cluster mission, launched in 2000, consists of four identical spacecraft in polar orbits around the Earth. The spacecraft fly in formation, and the orbits have thus far been designed so that the spacecraft form a regular tetrahedron in regions of scientific interest. The tetrahedron scale size has been varied periodically throughout the mission from scales of a few hundred kilometers to >1Re (Earth radius). The design and the operational history of the mission are reviewed, and plans for extension of the mission to 2009 are discussed. Different multipoint measurement techniques are also described. In particular, we review those techniques relevant to magnetic field analysis: the 'curlometer', the wave telescope/ k-filtering and discontinuity analysis. Emphasis will be placed on the usefulness of these techniques, and on the ways in which they render multi-point observations more versatile than those derived from single spacecraft. In the second part of the talk, we will discuss the use of these techniques to search for and study slow shocks in the magnetotail. Collisionless slow shocks are important plasma pheomena in their own right, as well as being important to theories of magnetic reconnection. We will discuss how techniques applied to observations of the bow shock can be adapted and used to study the morphology of slow shocks, and present candidate observations from the Cluster dataset. In the third part of the talk, we will discuss some recent observations of the magnetotail plasma sheet, which illustrate how single and multi-spacecraft observations can lead to very different conclusions concerning magnetotail dynamics. The implications for the re-interpretation of single spacecraft observations are considered.