MHD Turbulence Mediated by the Plasmoid Instability*

Magnetohydrodynamic (MHD) turbulence regulates the transfer of energy from large to small scales in many astrophysical systems, from the solar corona and accretion disks to the interstellar medium and galaxy clusters. An important feature of MHD turbulence is the tendency to develop sheets of strong electric current density. These current sheets are natural sites of magnetic reconnection, leading to the formation of plasmoids that eventually disrupt the sheet-like structures in which they are born. In this presentation, we investigate the role of the plasmoid instability in both 2D and 3D MHD turbulence by means of high-resolution direct numerical simulations at large magnetic Reynolds numbers. By breaking elongated current sheets into chains of small plasmoids, magnetic reconnection leads to a new range of the turbulent energy cascade in the energy spectra, where the rate of energy transfer is controlled by the growth rate of the plasmoids. The omnipresence of plasmoids and their consequences on, e.g., the solar coronal heating can be further explored with current and future satellites/telescopes.