B} > 
\label{mean}$$ The effect of the turbulent velocity is to introduce the standard extra terms representing the $\alpha$-effect with $$\alpha = 2C(0) = 
-{1 \over 3} \int <{\bf v}_T({\bf x}, t).{\bf \nabla} \times 
{\bf v}_T({\bf x},s) > ds$$ and an extra turbulent contribution to the diffusion $$\eta_T = T_{LL}(0) = {1 \over 3} \int <{\bf v}_T({\bf x},t).
{\bf v}_T({\bf x},s)> ds .$$

Over and above these terms the effect of ambipolar drift is to introduce an extra EMF represented by the last term in Eq. (\[mean\]) . This extra term involves the third moment of the magnetic field. Similarly as we will see below a consideration of the equation for the magnetic correlation function will introduce the fourth moment of the magnetic field. This will lead to an infinite hierarchy of equations for the moments which can be only truncated by assuming some form of closure. We assume below, for analytic tractability, that the magnetic field fluctuation $\delta {\bf B} =
{\bf B} -{\bf B}_0$ is also a homogeneous, isotropic, Gaussian random field with zero mean. Its equal time two point correlation is given by $$<\delta B^i({\bf x},t) \delta B^j({\bf y},t) > = M^{ij}(r,t) = 
M_N[\delta^{ij} -({r^i r^j \over 