Recorded 31 January 2025. Frank Stefani of the Helmholtz-Zentrum Dresden-Rossendorf presents "Harmonically forced and synchronized dynamos: theory and experiments" at IPAM's Rotating Turbulence: Interplay and Separability of Bulk and Boundary Dynamics Workshop. Abstract: In the first part of the talk, we examine the influence of tide-like forcings on Rayleigh-Bénard convection. We show how the helicity oscillations, which are typically connected with the sloshing and torsional oscillations of the large scale circulation, are synchronized by the external forcing. Thus motivated, we discuss a model of the solar dynamo that explains its various periodicities on widely different time scales in a self-consistent manner. Starting with Rieger-type periodicities, we show that the two-planet spring tides of Venus, Earth and Jupiter are able to excite magneto-Rossby waves in the solar tachocline with periods between 100 and 300 days and amplitudes of m/s or even more. We show that the quadratic action of these waves contains a beat period of 11.07 years, and argue that the axisymmetric part of the resulting alpha-effect is strong enough to synchronize the entire solar dynamo via parametric resonance. A secondary beat between the arising 22.14-year Hale cycle and the 19.86-year periodic motion of the Sun around the barycentre of the solar system may explain the longer-term Gleissberg and Suess-de Vries cycles. The spectrum emerging from this double-synchronized dynamo model is in remarkable agreement with climate-related data. In the last part of the talk, we review the present status of the DRESDYN precession-driven dynamo experiment. Its motivation stems, first, from the possible influence of the various Milankovic cycles on the geodynamo and, second, from the not yet fully understood spin-orbit coupling effects in our solar dynamo model. We discuss the combined numerical and experimental efforts to identify dynamo-optimizing precession ratios and nutation angles, and present very first results of the water experiments that were carried out at the big machine. Learn more online at: https://www.ipam.ucla.edu/programs/workshops/rotating-turbulence-interplay-and-separability-of-bulk-and-boundary-dynamics/