Speaker
Description
This study leverages a fully compressible 3D Hall-MHD numerical simulation of space plasma turbulence to explore multiscale coupling between streamlines and magnetic field line topologies, turbulent cascade rate, and energy dissipation. Through gradient tensor geometric invariants, we investigate the interplay between large-scale fluid dynamics and small-scale dissipative phenomena. From an intuitive standpoint, the second geometric invariant represents the balance between rotation and strain rates, whereas the third geometric invariant is associated with the interplay between vortex stretching and strain self-amplification, so they contain important information about the local field line configuration. The different terms contributing to the energy transfer rate (namely, Reynolds-Maxwell stress tensor, MHD and Hall terms) are estimated through the subgrid-scale terms arising from the coarse-graining of the Hall-MHD equations. We show how the direct cascade locally develops in where plasma is characterized by strain-dominated streamline structures and unstable stretching vortices, whereas stable vortices tend to back-transfer the turbulent energy towards larger scales. The viscous and ohmic dissipation estimated on the finer grid scale of the simulation organizes streamline and magnetic field line structures in a clear pattern. The correlation is then investigated by coarse-graining the fields to get insight on the self-organization between inertial- and ion-scale structures and the dissipation field. We highlight important clues about energy dissipation by analyzing inertial- and ion-scale field line structures. Finally, we simulate virtual multi-spacecraft measurements through the simulation mimicking a two nested-tetrahedra constellation, and we implement multipoint gradient estimations with the aim of highlighting the importance of this science for the ESA Phase A Plasma Observatory mission.
