Interaction between reconnection and Kelvin–Helmholtz at the high-latitude magnetopause

On March 23, 2002, Cluster satellites recorded an event, which has been interpreted as reconnection, during an outward crossing near the dawn side cusp region in the Northern Hemisphere. The event showed a large perturbation in the magnetic normal component, inconsistent with a one-dimensional reconnection layer configuration, and causing a poor result in a minimum magnetic variance analysis. The utilization of the plasma velocity or electric field data significantly improves the boundary normal analyses. Through the comparison between observational data and local three-dimensional MHD simulations, it is demonstrated that this perturbation is likely an indication of a strong boundary modulation by a KH wave. The event is used to examine several established and new boundary normal analysis methods.