Energy conversion inside Kelvin-Helmholtz Vortices

The Kelvin–Helmholtz instability (KHI) is a shear-driven phenomenon that generates a chain of vortices, located along the shear layer. As these vortices grow, they interact and fragment, eventually leading to turbulence and the dissipation of kinetic energy. The exact pathway through which KHI moves and converts energy across scales still remains elusive. Using Magnetospheric Multiscale (MMS) spacecraft data, we explore energy conversion pathways during KHI events at Earth's magnetopause.

We quantify, for the first time, KHI energy conversion channels via pressure–strain and J·E′ diagnostics. Enhanced energy conversion between flow and thermal energy is observed inside vortices, associated with both local non-thermal features and perpendicular temperature anisotropies. Conversely, at the boundaries, enhanced magnetic fluctuations are associated with peaks in the ion agyrotropy. Finally, we investigate how reconnecting current sheets, observed at the vortex boundaries, affect energy conversion terms.