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The Extended Cycle of Solar Activity and the Sun’s 22-Year Magnetic Cycle

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Abstract

The Sun has two characteristic migrations of surface features—the equatorward movement of sunspots and the poleward movement of high-latitude prominences. The first of these migrations is a defining aspect of the 11-yr Schwabe cycle and the second is a tracer of the process that culminates in solar polarity reversal, signaling the onset of the 22-yr magnetic cycle on the Sun. Zonal flows (torsional oscillations of the Sun’s differential rotation) have been identified for both of these migrations. Helioseismology observations of these zonal flows provide support for the extended (>11-yr cycle) of solar activity and offer promise of a long-term precursor for predicting the amplitude of the Schwabe cycle. We review the growth of observational evidence for the extended and 22-yr magnetic cycles and discuss: (1) the significance of latitude ∼50∘ on the Sun; (2) the “over-extended” cycle; and (3) the outlook for solar cycle 25.

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Acknowledgements

I thank André Balogh, Hugh Hudson, Kristóf Petrovay, and Rudolf von Steiger for organizing a timely and stimulating workshop. I am grateful to: Dick Altrock, Rainer Arlt, Sara Martin, Alexei Pevtsov, and Leif Svalgaard for helpful comments/discussions, Tom Bogdan for providing the text of A. Maunder’s letter, and Rachel Howe for providing updated/modified versions of Figs. 16, 17, and 18.

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    E. W. Cliver

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Cliver, E.W. The Extended Cycle of Solar Activity and the Sun’s 22-Year Magnetic Cycle. Space Sci Rev 186, 169–189 (2014). https://doi.org/10.1007/s11214-014-0093-z

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