### abstract

- 正The nonlinear mean-field dynamo due to a shear-current effect in a nonhelical homo- geneous turbulence with a mean velocity shear is discussed. The transport of magnetic helicity as a dynamical nonlinearity is taken into account. The shear-current effect is associated with the W× J term in the mean electromotive force, where W is the mean vorticity due to the large-scale shear motions and J is the mean electric current. This effect causes the generation of large-scale magnetic field in a turbulence with large hy-drodynamic and magnetic Reynolds numbers. The shear-current dynamo requires 3D random velocity field and is determined by the second-order moment of the velocity field. These shear dynamos with a zero net helicity are studied for small and large magnetic and hydrodynamic Reynolds numbers, and small shear using different approaches. The magnetic helicity ux strongly …