On September 21, The Astrophysical Journal published the 3D numerical work on a current sheet (CS) related to the coronal mass ejection (CME), Dr. YE from Yunnan Observatories of Chinese Academy of Sciences and his cooperators investigate the thermodynamics on the confined turbulence within the large-scale CS.

During a solar eruption, a significant amount of magnetic energy, equivalent to billions of giant hydrogen bombs exploding simultaneously, is converted into kinetic and thermal energies of plasma and the kinetic energy of energetic particles via magnetic reconnection. The CS self-consistently generated between the CME and the flare arcade is the core region where magnetic reconnection occurs. Previous study on the magnetic reconnection process within the CME-driven CS has mainly been limited to 2D simulations, but recent observations report that there are many 3D features in the eruption events. Therefore, further study on the 3D turbulent fine structures in CMEs will greatly improve our understanding of the energy conversion process during solar eruptions.

Using the 3D high-resolution Magnetohydrodynamical (MHD) simulations, researchers analyzed in details the complex geometric structures and thermodynamical features of the highly dynamical CME-flare CS based on the Titov & Démoulin model. They found that turbulence induced by plasmoid instabilities can locally give rise to a higher reconnection rate, and the elongated blobs undergo the splitting, merging and kinking processes in a more complex way in 3D. The plasma heating of the CS is mainly dominated by adiabatic and numerical viscous terms, and thermal conduction is the dominating factor that balances the energy within. 

As the CS develops very long, the turbulence anisotropy varies with height, showing a significant variation in the spectra of different characteristic regions of the CS. 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. In other words, various types of magnetic reconnection can occur simultaneously thanks to the local turbulence.

This study also helps to better understand the Extreme Ultra-violet features of the CS in the 3D view and provides important theoretical goals for the solar proximity exploration mission in the future.

Contact:
YE Jing
Yunnan Observatories, CAS
Email:yj@ynao.ac.cn