Evolution of anisotropic turbulence in nonlinear magnetic reconnection

Abstract

The anisotropy properties of magnetohydrodynamic turbulence in a sheared magnetic field are analyzed through a three-dimensional numerical simulation that reproduces the linear and nonlinear stage of a tearing instability. Far from the current sheet, the energy spectrum develops perpendicularly to the local magnetic field, as in homogeneous configurations. Within the current sheet, the spectrum anisotropy is also affected by the structure of unstable modes. With increasing time, the configuration becomes more turbulent, the former effect disappears, and the energy cascade takes place perpendicularly to the local magnetic field. The local spectrum becomes increasingly anisotropic while the spatially integrated spectrum tends to isotropize. There is the possibility that these properties could be used to identify the nonlinear stage of magnetic reconnection in space and laboratory plasmas, as well as to identify the particle transport regime in the considered magnetic configuration.