Speaker
Description
We present a solar dynamo model that appears capable of explaining various periodicities across a wide range of timescales in a self-consistent manner [1]. Starting with Rieger-type periodicities, we demonstrate that the two-planet spring tides of Venus, Earth, and Jupiter can excite magneto-Rossby waves in the solar tachocline. These waves have typical periods ranging from 100 to 300 days, and can reach amplitudes of metres per second or greater [2,3].
The first beat period, derived from the three tidally-excited waves, is 1.723 years. This aligns remarkably well with the observed period of the quasi-biennial oscillation (QBO) [1, 4]. The QBO could also help explain the astonishing regularity and calmness of the solar dynamo, a long-standing mystery.
The second beat period of 11.07 years, which arises from these three waves, corresponds to the long-term mean value of the Schwabe cycle. We hypothesise that the axisymmetric component of the α-effect, caused by these waves, is strong enough to synchronise the entire solar dynamo via parametric resonance [5].
Finally, we demonstrate that another beat, occurring between the 22.14-year Hale cycle and the Sun's 19.86-year periodic motion around the solar system's barycentre, could account for the Suess-de Vries cycle, which has a period of 193 years. The resulting spectrum of this double-synchronised dynamo model is found to be in very good agreement with climate-related data obtained from varved sediments in the Lake Lisan region [3, 6].
References
[1] Stefani, F. et al., Solar Phys. 300, 110 2025.
[2] Horstmann, G.M. et al., Astrophys. J. 944, 48 (2023)
[3] Stefani, F. et al., Solar Phys. 299, 51 (2024)
[4] Stefani, F. et al., https://arxiv.org/abs/2602.11227 (2026)
[5] Klevs M. et al. Solar Phys. 298, 90 (2023)
[6] Prasad, S. et al., Geology 32, 581 (2004)