Self-organization of Local Streamline Structures and Energy Transfer Rate in Compressible Plasma Turbulence

Compressible fluctuations represent a key element of turbulence in astrophysical plasmas, where the compression and expansion of turbulent flows play a critical role in regulating energy transfer and dissipation. In this work, we examine how local streamline topology and energy cascade rate self-organize in plasma turbulence at a fixed scale. Using a fully compressible Hall-magnetohydrodynamic simulation, we quantify the subgrid-scale energy transfer and analyze its relationship to streamline structures by means of gradient-tensor geometric invariants of the velocity field. Our results highlight how streamline topology is crucial for diagnosing turbulence, since the direction of the energy transfer rate is found to be shaped by the local streamline topology. Compressible fluctuations, on the contrary, do not show a clear topological selection in the energy transfer since the overall direction of the local cascade rate is found to be determined by the sign of −∇ · u (plasma volumetric compression or expansion).