  We consider dynamo action under the combined influence of turbulence and
large-scale shear in sheared jets. Shear can stretch turbulent magnetic field
lines in such a way that even turbulent motions showing mirror symmetry become
suitable for generation of a large-scale magnetic field. We derive the integral
induction equation governing the behaviour of the mean field in jets. The main
result is that sheared jets may generate a large-scale magnetic field if shear
is sufficiently strong. The generated mean field is mainly concentrated in a
magnetic sheath surrounding the central region of a jet, and it exhibits sign
reversals in the direction of the jet axis. Typically, the magnetic field in a
sheath is dominated by the component along the jet that can reach equipartition
with the kinetic energy of particles, The field in the central region of jets
has a more disordered structure.
