Speaker
Description
Turbulence and energy dissipation in space plasmas remain major open
questions, especially in weakly collisional environments such as the Earth’s magnetosheath. While turbulence is known to cascade energy across scales, the mechanisms by which this energy is concentrated into localized dissipation are still not well understood. One theory suggests that turbulence drives energy dissipation through coherent structures. These are small-scale regions of intense turbulent activity that may serve as preferential sites for energy conversion. Previous studies reported only weak to moderate correlations between turbulent structures and sites of enhanced dissipation. This may be due to the observed spatial displacement between these structures and the locations where their energy is ultimately dissipated.
In this study, we identify coherent structures using the Local Energy Transfer (LET), derived from the Politano–Pouquet law of 1998 (PP98). This proxy is then statistically correlated with several kinetic dissipation measures, each providing a unique insight into the dissipation mechanisms. These include the Zenitani parameter, pressure–strain interaction, pressure agyrotropy, velocity-space non-Maxwellianity, and kinetic-entropy non-Maxwellianity.
The analysis is done using the 2023 Magnetospheric Multiscale Mission
(MMS) unbiased campaign to ensure a representative sample of turbulence.
To account for possible displacement between turbulent structures and sites of dissipation, we also apply a procedure that adjusts for temporal misalignment between the proxies.
Our results show that, when accounting for the displacement, turbulent
structures are moderately to strongly correlated with enhanced kinetic dissipation. Furthermore, the measured displacement between the two sites is on the order of a few ion scales. Finally, by using an unbiased dataset, these findings provide new robust evidence that support the view that coherent structures play a significant role in mediating plasma heating.
