Researchers from the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGGCAS), the University of Science and Technology of China and the Austrian Academy of Sciences have confirmed that interaction between magnetic flux ropes within the diffusion region of magnetic reconnection play a key role in the dynamics of magnetic reconnection and lead to turbulence. The work was published online in Nature Physics on December 7. 

Magnetic reconnection is a fundamental plasma process by which magnetic free energy can be released explosively to heat and accelerate plasma. Simultaneously, the magnetic topologic structure will be rearranged and matter can be transferred in different regimes. In 1946, the Australian scientist Ronald Giovanelli first proposed the conception of magnetic reconnection to explain the explosive energy release event in the solar atmosphere, called solar flare.  

After more than half a century, research has shown that magnetic reconnection is not only the main reason for solar flare but also can be the reason for a number of other explosive phenomena in nature, such as color mass emissions (CME), planetary storms and substorms, jets in accretion disks, sawtooth instability in Tokamaks, etc. However, how magnetic free energy is released and what the dynamic processes are in reconnection are still unclear and there is no extensively accepted theory so far. 

In order to reveal the dynamic process in the reconnection diffusion region and energy release mechanisms, the most effective and direct method is to analyze spacecraft data collected in that region. Using the highest time resolution data from the Cluster mission obtained in the magnetotail, researchers from IGGCAS and USTC demonstrated that the reconnection diffusion region is filled with magnetic flux ropes and the coalescence of these flux ropes can heat and accelerate plasma. Geophys. Res. Lett. reported the finding of thin current layers along the reconnection separatrices by these researchers in 2013 and 2014. 

Based on this previous work, researchers hypothesized that magnetic flux ropes are created by the breakup of the thin current layers. Furthermore, magnetic reconnection will evolve into turbulence due to the repeated formation and interaction of the flux ropes, as shown in the schematic. 

This work was sponsored by the National Science Foundation of China (NSFC), the National Basic Research Program of China and the Austrian Science Fund (FWF). 

A schematic for reconnection diffusion region (Image by IGG)