Magnetic helicity and the evolution of decaying magnetohydrodynamic
  turbulence
  Ensemble averaged high resolution direct numerical simulations of reverse
spectral transfer are presented, extending on the many single realization
numerical studies done up to now. This identifies this type of spectral
transfer as a statistical property of magnetohydrodynamic turbulence and thus
permits reliable numerical exploration of its dynamics. The magnetic energy
decay exponent from these ensemble runs has been determined to be $n_E = (0.47
\pm 0.03) + (13.9 \pm 0.8)/R_{\lambda}$ for initially helical magnetic fields.
We show for the first time that even after removing the Lorentz force term in
the momentum equation, thus decoupling it from the induction equation, reverse
spectral transfer still persists. The induction equation is now linear with an
externally imposed velocity field, thus amenable to numerous analysis
techniques. A new door has opened for analyzing reverse spectral transfer, with
various ideas discussed.
