title: Nonhelical inverse transfer of a decaying turbulent magnetic field.
abstract: In the presence of magnetic helicity, inverse transfer from small to large scales is well known in magnetohydrodynamic (MHD) turbulence and has applications in astrophysics, cosmology, and fusion plasmas. Using high resolution direct numerical simulations of magnetically dominated self-similarly decaying MHD turbulence, we report a similar inverse transfer even in the absence of magnetic helicity. We compute for the first time spectral energy transfer rates to show that this inverse transfer is about half as strong as with helicity, but in both cases the magnetic gain at large scales results from velocity at similar scales interacting with smaller-scale magnetic fields. This suggests that both inverse transfers are a consequence of universal mechanisms for magnetically dominated turbulence. Possible explanations include inverse cascading of the mean squared vector potential associated with local near two dimensionality and the shallower k^{2} subinertial range spectrum of kinetic energy forcing the magnetic field with a k^{4} subinertial range to attain larger-scale coherence. The inertial range shows a clear k^{-2} spectrum and is the first example of fully isotropic magnetically dominated MHD turbulence exhibiting weak turbulence scaling.
authors.affiliation: Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden.|Department of Astronomy, AlbaNova University Center, Stockholm University, 10691 Stockholm, Sweden.
authors.forename: Axel
authors.initials: A
authors.lastname: Brandenburg
authors.affiliation: The McWilliams Center for Cosmology and the Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA.|Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, Ontario P3E 2C, Canada.|Abastumani Astrophysical Observatory, Ilia State University, 3-5 Cholokashvili Avenue, Tbilisi GE-0194, Georgia.
authors.forename: Tina
authors.initials: T
authors.lastname: Kahniashvili
authors.affiliation: Faculty of Exact and Natural Sciences, Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128, Georgia.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Tevzadze