“…We base the modeling on the well-established von Kármán-Taylor 2,3 approach for energy decay phenomenology in hydrodynamics, that is, on the pair of equations du 2 / dt ϳ −u 2 / sp and dᐉ / dt ϳ ᐉ / sp , with the spectral transfer time sp identified with the global hydrodynamic nonlinear ͑or "eddy turnover"͒ time nl = ᐉ / u. Analogous equations for MHD 12,25,26,6 have been written as direct extensions of this isotropic homogeneous hydrodynamic case, and these have been found to account well for decaying MHD turbulence simulations. 6,27,28 Here, we will adopt a straightforward generalization to account for two evolving MHD components.…”