Princeton University Astroplasmas Seminar

The origin of cosmic magnetic fields remains an open problem in astrophysics.  In 1955, Eugene Parker proposed a mean-field dynamo theory by parameterizing the effects of small-scale turbulence.  Although this framework successfully reproduces observed large-scale magnetic fields, it relies on parameters that are difficult to constrain from first principles.  Here, by analyzing an unstable, driven shear flow, we develop analytic theory and perform three-dimensional simulations of turbulence with up to 4,096 × 4,096 × 8,192 grid points.  The simulations demonstrate ab initio generation of quasi-periodic, large-scale magnetic fields.  The generation operates via the mean-vorticity effect—an additional mean-field dynamo process postulated in 1990—and is driven by robust, large-scale, three-dimensional, nonlinear jets.  Predictions from the jet-driven dynamo are confirmed using data from a shear-driven laboratory dynamo experiment.  This dynamo mechanism applies to a variety of astrophysical systems, including binary neutron star mergers, where it can produce some of the strongest magnetic fields in the Universe, providing signals for multi-messenger astronomy.