Abstract
The Hale solar period, τH(1) ≃22 yr, and its second harmonic, τH(2)≃11 yr, which characterize the sunspot index and are thus hydromagnetic, are imprinted in certain varved rocks of Archaean1 to late Precambrian2 age, but the varves record climate and thus are sensitive to solar insolation2,3. We report here apparent collective behaviour of the two kinds of data. The 22-yr/11-yr amplitude spectral density (ASD) ratio, βi (i = 1) of the sunspot index (which is a measure of solar-cycle asymmetry), plotted together with βis from three ancient varve thickness sequences against the age for each βi, results in a remarkably close fit to a decreasing exponential with time constant τ≃2 Gyr. These varves and the sunspot index appear to link solar luminosity and the solar field, implying that a common forcing mechanism affects luminosity and the dynamo periods through the common decay time, τ.
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Sonett, C., Trebisky, T. Secular change in solar activity derived from ancient varves and the sunspot index. Nature 322, 615–617 (1986). https://doi.org/10.1038/322615a0
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DOI: https://doi.org/10.1038/322615a0
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