Generation of FTE Signatures by the Kelvin–Helmholtz Instability

Abstract

Magnetic reconnection and the Kelvin–Helmholtz instability (KHI) are the two fundamental processes in planetary magnetospheres that can lead to plasma, momentum, and energy transport across the magnetospheric boundary. Flux Transfer Events (FTEs), being characterized by the bipolar variation of the magnetic normal component, are often considered to be generated by magnetic reconnection. However, several possible mechanisms can also give rise to FTE-like features in the boundary layer and potentially mislead observational analysis; the KHI is one such candidate. Using two-dimensional magnetohydrodynamics (MHD) simulations, we examine and categorize the signatures observed by several virtual satellites as they pass through the Kelvin–Helmholtz waves along different trajectories. We have shown that the bipolar signatures were identified during the satellite's passage across the spine region and the leading/trailing edge of the KH vortex. The duration of bipolar signatures was also shown to vary depending not only on where the satellite trajectory intersects with the vortices, but also on the density asymmetry on both sides of boundary which in turn affects the relative motion between the vortices and satellite. Further, slight adjustments to the projection angle of the magnetic field are also applied in the simulations, as the signatures of the KHI are very sensitive to the in-plane magnetic field component. These results can be used as diagnostics when analyzing spacecraft data to help distinguish KHI-created signatures from FTE.