Effect of plasmoid instability on energy spectra at high magnetic Reynolds number 3D-magnetohydrodynamic turbulence using large eddy simulation*

Plasmoid instability in evolving current sheets has been studied in the past using 2D magnetohydrodynamic (MHD) simulations. The combined effect of reconnection and thin current sheets at the point of maximum current density during the evolution of flow, at large magnetic Reynolds number (Re_m), is favorable for the formation of plasmoid leading to disruption of current sheets. This causes emergence of plasmoid-mediated regime within the inertial sub-range with a slope steeper than -3/2. Previously conducted direct numerical simulations (DNS) show a slope of -2 in the inertial sub-range at small scales for Re_m ≅ 9200. To analyze plasmoid effects on the properties of three-dimensional (3D) flow, simulations at Re_m of Ο(10⁴) or higher need to be performed. Since high-Re_m DNS is limited by computational resources required to carry out the simulation, numerical analysis of incompressible decaying MHD turbulence at high Reynolds number using LES is a feasible alternative. The current study uses LES to analyze 3D high Re_m MHD turbulent flow at Re_m of 10⁴. The grid resolution in LES is such that the inertial subrange is resolved completely, so that the effect of plasmoid instability on the energy cascade and energy spectra at high Reynolds number can be demonstrated.