Abstract
Fossil records of presumed solar activity1,2 in 680-Myr-old varves reveal two periods, ∼314 and 350 varve years respectively, which also appear in recent sunspot records. These periodicities, combined with a nonlinear feature of sunspot number and a theory of the asymmetry of the solar cycle, enable the sunspot record to be extrapolated back to 1800 so well that the next magnetic cycle may be predicted. Fossil records offer the hope of going beyond numerical analysis into physics; one result is the demonstration that part of the 8–15 yr spread of the 11-yr cycle is due to shifts in the year of sunspot minimum caused by the 350-yr cycle. The annual sunspot number can be represented by3:
Rsim(t)=∣ℋ[Re{E(t)exp{i[ω0t+φ(t)]}}+U(t)]∣ (1)
where ω0 is the angular frequency corresponding to the magnetic period (∼22 yr), E(t) is an instantaneous envelope amplitude, φ(t) is the associated instantaneous phase, U(t) is an additive undulation of low amplitude, ℋ is a nonlinear function, and Rsim(t) is the estimated annual mean sunspot number. Here I consider these parameters, in turn, to derive an evaluation of equation (1) from AD 1800 to 2000.
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Bracewell, R. Simulating the sunspot cycle. Nature 323, 516–519 (1986). https://doi.org/10.1038/323516a0
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DOI: https://doi.org/10.1038/323516a0
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