  The mean electromotive force (MEMF) in a rotating stratified
magnetohydrodynamical turbulence is studied.Our study rests on the mean-field
magnetohydrodynamics framework and $\tau$ approximation. We compute the effects
of the large-scale magnetic fields (LSMF), global rotation and large-scale
shear flow on the different parts of the MEMF (such as $\alpha$ - effect,
turbulent diffusion, turbulent transport, etc.) in an explicit form. The
influence of the helical magnetic fluctuations which stem from the small-scale
dynamo is taken into account, as well. In the paper, we derive the equation
governing the current helicity evolution. It is shown that the joint effect of
the differential rotation and magnetic fluctuations in the stratified media can
be responsible for the generation, maintenance and redistribution of the
current helicity. The implication of the obtained results to astrophysical
dynamos is considered as well.

Astrophysics