  In the presence of large-scale vortical motions and/or magnetic-field
strains, the turbulent cross helicity (velocity--magnetic-field correlation in
fluctuations) may contribute to the turbulent electromotive force and the
Reynolds stress. These effects of cross helicity are considered to balance the
primary effects of turbulence such as the turbulent magnetic diffusivity in
magnetic-field evolution and the eddy viscosity in the momentum transport. The
cross-helicity effects may suppress the enhanced transports due to turbulence.
Physical interpretation of the effects is presented with special emphasis on
the difference between the cross-helicity effect and the usual $\alpha$ or
helicity effect in the dynamo action. The relative importance of the
cross-helicity effect in dynamo action is validated with the aid of a direct
numerical simulation (DNS) of the Kolmogorov flow with an imposed magnetic
field. Several mechanisms that provide turbulence with the cross helicity are
also discussed.

Solar and Stellar Astrophysics;Fluid Dynamics;Plasma Physics