A dynamo driven by zonal jets at the upper surface: Applications to giant planets

► We model dynamo action driven by unstable zonal jet currents in a rotating sphere. ► Rapid zonal jets are unstable to inviscid barotropic instability (Rossby waves). ► The Rossby wave lengthscale controls the generation of axisymmetric magnetic field. ► This dynamo model may be relevant for the giant planets.