Tidal triggers and the predictability of solar activity

Magneto-Rossby waves in the solar tachocline are currently considered to be one of the main determinants of solar activity. In particular, they can give rise to the quasi-biennial oscillation (QBO). The latter was recently shown to be dominated by a phase-stable period of around 1.7 years. By analyzing 72 ground-level enhancement (GLE) events and 37 S-flares, we determine that this period is close to 1.723 years. This, in turn, is the dominant beat between the periods of the spring tides of the tidally dominant planets Venus, Earth, and Jupiter, which are suspected to synchronize not only the QBO, but also the 11.07-year Schwabe cycle. We demonstrate that recent events, such as the solar storm of 2024 May 10 and the strong X-flare of 2026 February 1, align well with maxima of the tidal forcing. By contrast, the Carrington event (1959 September 1) does not fit this pattern.

💡 Research Summary

The paper proposes that planetary tidal forces, specifically the spring tides of Venus‑Jupiter (≈118 days), Earth‑Jupiter (≈199 days) and Venus‑Earth (≈292 days), act as a periodic driver for magneto‑Rossby waves in the solar tachocline. These waves are suggested to generate a quasi‑biennial oscillation (QBO) with a dominant period of about 1.7 years, which the authors identify as a beat frequency of the three tidal components. To test this hypothesis, the authors compile two independent solar‑activity data sets: 72 ground‑level enhancement (GLE) events from 1956–2025 and 37 S‑class solar flares (≥X10) from 1978 onward.

For each event time t_i they compute a correlation measure Corr = Σ cos(2π t_i/T₀ + φ) / √