By Andy May
Dr. Frank Stefani and colleagues from Helmholtz-Zentrum Dresden – Rossendorf and the Institute for Numerical Modelling, University of Latvia, have proposed a new physically consistent model of solar variability. It proposes that the known solar cycles, from the eleven-year Schwabe cycle to the 193-year De Vries cycle are related to planetary orbits and the 19.86-year solar oscillation around the solar system barycenter.
The paper, “Rieger, Schwabe, Suess-de Vries: The Sunny Beats of Resonance,” explains the details of the concept. The press release, which is easier to read, explains the implications.
Astronomers and physicists have long been writing about the possible solar tidal effects of the planets, see Scafetta and Bianchini’s review paper here. The planetary orbits must affect the solar plasma in some fashion and the orbital patterns do correlate to proposed solar and climate cycles. While the statistical correlation was good, the underlying physics of why it all worked remained elusive.
Stefani and his colleagues have created a physically consistent model of the 193-year De Vries solar and climate cycle, the longest solar cycle physically modeled to date. There are longer solar cycles, such as the famous ~2450-year Bray cycle and the ~1,000-year Eddy Cycle, that have been observed but not modeled as precisely yet. This is an important start.
Stefani, F., Horstmann, G.M., Klevs, M. et al. Rieger, Schwabe, Suess-de Vries: The Sunny Beats of Resonance. Sol Phys 299, 51 (2024). https://doi.org/10.1007/s11207-024-02295-x (link)
Stefani et al have the right period, which they found from Ian Wilson. The 193-year period is the solar magnetic cycle, but it’s not the de Vries cycle. Ian Wilson’s paper: http://www.pattern-recogn-phys.net/1/147/2013/prp-1-147-2013.pdf (See Fig.12). He also discusses ‘the 208 yr de Vries cycle’ in section 4.3
The climate de Vries cycle is an average of poorly observed climatic effects. The de Vries solar cycle is the presumed cause of it. The difference in their periods is probably accounted for by varying delays in the impact of the solar cause.
The climate state varies according to multiple oscillations (see Wyatt and Curry, 2013, “Role for Eurasian…”). Overall they form a 67-year climate oscillation. What point in that oscillation the solar cycle occurs matters, so the 208-average and the 193-year solar cycle are close enough because they remain in phase. I argue that the 208 average is just slightly off.