Propagation of Alfvén Waves at the Plasma Sheet Boundary Layer

Recently, observations from the Polar and Cluster satellites have indicated that largeamplitude kinetic Alfvén waves are observed throughout the plasma sheet, particularly at the plasma sheet boundary layers, during substorms. These waves may be directly produced by reconnection processes in the tail, or indirectly through linear or nonlinear mode conversion or by localized plasma flows in the tail. The generation and propagation of these waves is studied through a consideration of the twofluid and kinetic linear dispersion relations as well as through nonlinear MHD simulations of wave propagation at the boundary layer.