Generation of the magnetic field in jets
Departament de Física Aplicada, Universitat d'Alacant, Ap. Correus 99, 03080 Alacant, Spain e-mail: email@example.com
2 A.F. Ioffe Institute of Physics and Technology and Isaak Newton Institute of Chili, Branch in St. Petersburg, 194021 St. Petersburg, Russia
Accepted: 17 April 2006
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.
Key words: magnetohydrodynamics (MHD) / ISM: jets and outflows / galaxies: jets / ISM: magnetic fields / gravitational lensing / magnetic fields
© ESO, 2006