Three-dimensional Simulation of Thermodynamics on Confined Turbulence in a Large-scale CME-flare Current Sheet

Abstract

Turbulence plays a key role in forming the complex geometry of the large-scale current sheet (CS) and fast energy release in a solar eruption. In this paper, we present full 3D high-resolution simulations for the process of a moderate coronal mass ejection (CME) and the thermodynamical evolution of the highly confined CS. Copious elongated blobs are generated owing to tearing and plasmoid instabilities, giving rise to a higher reconnection rate, and undergo the splitting, merging, and kinking processes in a more complex way in 3D. A detailed thermodynamical analysis shows that the CS is mainly heated by adiabatic and numerical viscous terms, and thermal conduction is the dominant factor that balances the energy inside the CS. Accordingly, the temperature of the CS reaches to a maximum of about 20 MK, and the range of temperatures is relatively narrow. From the face-on view in the synthetic Atmospheric Imaging Assembly 131 Å, the downflowing structures with similar morphology to supra-arcade downflows are mainly located between the post-flare loops and loop top, while moving blobs can extend spikes higher above the loop top. The downward-moving plasmoids can keep the twisted magnetic field configuration until the annihilation at the flare loop top, indicating that plasmoid reconnection dominates in the lower CS. Meanwhile, the upward-moving ones turn into turbulent structures before arriving at the bottom of the CME, implying that turbulent reconnection dominates in the upper CS. The spatial distributions of the turbulent energy and anisotropy are addressed, which show a significant variation in the spectra with height.

A method for determining the locations and configurations of magnetic reconnection within three-dimensional turbulent plasmas

“…The theory of global reconnection is well-defined but is not convenient to directly apply for analyzing discrete magnetic data, especially for cases with strong turbulence. As revealed by various high-resolution simulations, the 3D reconnection regions are composed of multi-scale current sheets that are far more complex than theoretical models (see Dong et al 2022;Wang et al 2023;Ye et al 2023), which significantly enhances the difficulties in selecting appropriate start and end positions for field-line mappings. Complete samplings of field lines within the entire system might produce reliable results, which, however, can hardly be operated as limited by computational resources and numerical integration errors.…”

The Lorentz Force at Work: Multiphase Magnetohydrodynamics throughout a Flare Lifespan

“…This should be contrasted with the simulations (in zero-beta settings, i.e., without thermodynamics) of actual eruptions that have provided insight into the evolving topological evolutions where an initial unstable flux rope is present (Aulanier et al 2012). Such eruptive models, extended to full thermodynamics and concentrating on the current sheet fine-structure (Ye et al 2023), are currently feasible thanks to adaptive mesh refinement strategies provided by our open-source code MPI-AMRVAC (Keppens et al 2023).…”