{\bf \nabla } \times ( {\bf v}_T({\bf x},s)\times {\bf B}({\bf x},0))] $ and ${\bf V}={\bf v}_n +{\bf v}_D$. We have also retained only terms which are potentially of order $\delta t$, and so will survive in the limit $\delta t \to 0$. Note that the last term in the above equation is potentially first order in $\delta t$, because of the presence of the stocahstic turbulent velocity field ${\bf v}_T$.

The time evolution of the mean magnetic field ${\bf B}_0=<{\bf B}>$ can be deduced by taking the ensemble average of Eq. (\[sol\]) . As before $<>$ denotes averaging over an ensemble of the stochastic velocity field ${\bf v}_T$. On using the fact that ${\bf v}_T$ at time $t$ is not correlated with either the initial magnetic field ${\bf B}({\bf x},0)$ or the initial perturbed field $\delta {\bf B}({\bf x},0) = {\bf B} - <{\bf B} >$ and taking the limit $\delta t \to 0$ we get after some straight forward algebra $${\partial {\bf B}_0\over \partial t} =
{\bf \nabla } \times [ {\bf v}_0 \times {\bf B}_0 + 2C(0) {\bf B}_0
 -(\eta  +T_{LL}(0) )
 {\bf \nabla } \times {\bf B}_0 ]  +
< {\bf \nabla} \times 
{\bf v}_D \times {\bf 