Speaker
Description
The predominant magnetic backreaction channel through which the growth of solar/stellar dynamos is stabilized has not yet been identified with confidence. In this work, we investigate the dynamical feedback on differential rotation directly driven by the Lorentz force associated with the cycling large-scale magnetic field, in an otherwise kinematic dynamo model where the Babcock-Leighton mechanism is used to regenerate the large-scale dipole. We explore the dynamical regimes in which this saturation occurs efficiently and find that a very weak reduction of the average differential rotation, and even weaker torsional oscillation patterns, are sufficient to stabilize the dynamo, from weakly to highly supercritical dynamo solutions, as well as for Prandtl numbers approaching unity. Acting jointly with the time-delay dynamics that characterize flux- transport dynamos operating in or close to the advection-dominated regime, the dynamical feedback produces a variety of deterministic long-timescale modulations that are strongly enhanced by stochastic forcing. As such, an accurate characterization of long- timescale solar activity modulations, as obtained from cosmogenic isotopes, can provide useful constraints on the saturation mechanism(s) of solar and stellar dynamos.