The Magnetic Helicity Driven Solar-Type Dynamo

(1) Theoretical studies have shown that large-scale vorticity generates a divergent-type helicity flux associated with small-scale magnetic fluctuations. Similar to the $\alpha$-effect, this mechanism breaks the equatorial reflection symmetry of magnetic fluctuations in stellar convection zones. This contribution has been termed the new Vishniac flux (hereafter NV flux). (2) Methods: We employ a mean-field dynamo model to investigate the influence of the NV flux on solar-type dynamos. (3) Results: We find that the NV flux leads to an enhancement of the dynamo efficiency for the turbulent generation of the large-scale poloidal magnetic field in the Sun. The dynamical impact of the NV flux on the evolution of the magnetic field results in a concentration of dynamo waves toward the equatorial region. Using numerical simulations of the mean-field dynamo, we compare the helicity production rates arising from different turbulent dynamo mechanisms, namely the $\alpha$-effect and the NV flux. The model demonstrates that the new dynamo source associated with large-scale vorticity and small-scale dynamo action leads to an amplification of poloidal field generation in the polar regions near the top of the dynamo domain. (4) Conclusions: Any fluctuating magnetic activity arising within the differentially rotating stellar convection zone can serve as an additional source for the generation of the large-scale poloidal magnetic field of a star.