Quantitative Analysis of Energy Conversion and Anomalous Transport in Kelvin-Helmholtz Instabilities at the Magnetopause

The magnetopause is the boundary where the solar wind interacts with the Earth's magnetosphere, playing a crucial role in the transfer and exchange of mass, momentum, and energy. The Kelvin-Helmholtz instability (KHI) is widely recognized as a key mechanism facilitating plasma transport across the magnetopause. However, direct observational evidence remains lacking. Using high-resolution data from the Magnetospheric Multiscale (MMS) mission, we investigated a KHI event by quantitatively analyzing the energy conversion rate, anomalous flow velocity, and anomalous diffusion coefficient associated with electromagnetic perturbations across various frequency ranges. Our results demonstrate that both the primary KHI and its internal small-scale structures contribute significantly to energy conversion, with the primary KHI producing larger anomalous flows and diffusion coefficients than its internal structures. The peak anomalous diffusion coefficient driven by the KHI (~2 × 10¹⁰ m²/s) is an order of magnitude greater than that induced by lower-hybrid drift waves in the magnetopause reconnection boundary layers. These findings provide quantitative evidence of the critical role played by the KHI and its internal small-scale structures in plasma transport and energy conversion at the flank region of magnetopause.