Kelvin-Helmholtz Waves/Vortices and Magnetic Flux Ropes at Earth's Magnetopause

Abstract:

Kelvin-Helmholtz (KH) waves/vortices and magnetic flux ropes at Earth's magnetopause are important ingredients in the solar wind-magnetosphere interaction. KH instabilities are excited in a velocity shear layer, leading to an undulation of the magnetopause or inner edge of its boundary layer and eventually to the formation of flow vortices, while flux ropes are generated in a current sheet through a time-dependent form of magnetic reconnection, which interconnect the field lines on both sides of the magnetopause. Because of their two- or three-dimensional nature, in-depth observational studies have become possible only with the advent of multi-spacecraft missions such as Cluster and THEMIS. We discuss similarities/differences of these two phenomena and the roles of these processes in the transfer of mass, momentum, and energy across the magnetopause, in particular with regard to the formation of the low-latitude boundary layer. Recent advances in studies of three-dimensional effects on these phenomena, effects of nonlinear evolution of the KH instability on magnetic reconnection and flux rope generation, and dawn-dusk symmetry/asymmetry in and IMF dependence of the occurrence of nonlinear (overturned) KH waves are also presented.