Guervilly C. auteur aut IRD Cardin Philippe auteur aut IRD Schaeffer N. auteur aut IRD text journalArticle eng We present a dynamo mechanism arising from the presence of barotropically unstable zonal jet currents in a rotating spherical shell. The shear instability of the zonal flow develops in the form of a global Rossby mode, whose azimuthal wavenumber depends on the width of the zonal jets. We obtain self-sustained magnetic fields at magnetic Reynolds numbers greater than 10(3). We show that the propagation of the Rossby waves is crucial for dynamo action. The amplitude of the axisymmetric poloidal magnetic field depends on the wavenumber of the Rossby mode, and hence on the width of the zonal jets. We discuss the plausibility of this dynamo mechanism for generating the magnetic field of the giant planets. Our results suggest a possible link between the topology of the magnetic field and the profile of the zonal winds observed at the surface of the giant planets. For narrow Jupiter-like jets, the poloidal magnetic field is dominated by an axial dipole whereas for wide Neptune-like jets, the axisymmetric poloidal field is weak. specialized Magnetic fields Jupiter, Interior Neptune, Interior Rotational dynamics 020 060 218 1 100-114 2012 0019-1035 https://www.documentation.ird.fr/hor/PAR00008692 10.1016/j.icarus.2011.11.014 0019-1035 https://www.documentation.ird.fr/hor/PAR00008692 IRD - Base Horizon / Pleins textes 2012-05-04 2017-08-23 PAR00008692 fre