Comparison of Kelvin-Helmholtz Instability in the Two- and Three-Dimensional Configurations

The Kelvin–Helmholtz (KH) instability is often regarded as one of the most important mechanisms for viscous interaction between the shocked solar wind and the Earth's magnetosphere. It has been observed that KH instability can operate under varies interplanetary magnetic field (IMF) orientations (i.e., north-/southward, dawn-/duskward, Parker spiral and ortho-Parker spiral orientations). Nonlinear KH waves can form thin current layers by dramatically twisting the magnetic field, and consequently triggers magnetic reconnection, which was first illustrated by local two-dimensional (2-D) MHD simulations and was later confirmed by several in-situ observational events. Recently, local three-dimensional (3-D) simulations showed that nonlinear KH instability in the 3-D geometry is fundamentally different from 2-D geometry. Note that most of the KH in-situ observational events are localized at low latitudes and are compared with 2-D scenarios. It is of interest to ask the question what can be misinterpreted if the third dimension is ignored for the nonlinear KH mode. This presentation will provide a systematic comparison between 2-D and 3-D nonlinear KH mode under different IMF orientations, and discuss the potential influence of the interpretation of observational signatures.