Investigating the role of magnetic reconnection in helical and non-helical MHD decaying turbulence*

Magnetically dominated decaying turbulence occurs in various astrophysical systems on scales from cosmological to stellar. It gains importance because such a decaying system leads to inverse transfer of magnetic energy. Recently, it was found that the physical mechanism for the inverse energy transfer is magnetic reconnection. Previously, Bhat et al.¹ have shown that decay laws are the same in 2D and 3D for nonhelical turbulent system. Through this project, we showed that helical decaying turbulence also follows the same 2D (or 2.5D)-3D correspondence. We also showed, this type of correspondence in the nonhelical case likely rules out the possibility of Saffman helicity invariant being the constraining quantity (contradicting Hosking and Schekochihin²). We find anastrophy conservation has close links with magnetic reconnection in nonhelical 2D, and this carries over to 3D as well, due to a quasi-two-dimensionalization, which is typical of magnetically dominated systems. We used Minkowski functionals to characterize the anisotropy of the 3D decaying turbulent system.

 

¹https://academic.oup.com/mnras/article-abstract/501/2/3074/6039338?redirectedFrom=fulltext

² https://journals.aps.org/prx/pdf/10.1103/PhysRevX.11.041005