Cycle 24

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Nugget
Number:	91
1st Author:	Hugh Hudson
2nd Author:	Steven Christe
Published:	22 December 2008
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Introduction

This Nugget picks up the discussion of the somewhat tardy Solar Cycle with the (arbitrary) identification number 24. The increase of sunspots into the next cycle maximum should be starting shortly - but hasn't yet. Here we discuss how perplexing this is, considering some of the options, and then briefly review our workshop devoted to planning for the new cycle. We also discuss an innovation - the reporting of the workshop activities in this Wiki.

Solar Cycles

As is well known, sunspot numbers go up and down with an 11-year period, which turns out to be half of the 22-year "Hale cycle" (George Ellery Hale discovered solar magnetism, and it turns out that alternate 11-year cycles have mirror-image latitude distributions of magnetic polarity. Richard Carrington, a 19th-century solar astronomer who made many discoveries, started the counts of 11-year "Carrington cycles." We find ourselves just finished with the 23rd Carrington cycle, and hoping for a 24th to happen. New sunspots have always before emerged roughly on schedule, except for the interesting period of the Maunder Minimum, a period in the late 17th century when sunspots almost disappeared. This had many interesting implications, including those related to tree rings.

There is currently a slow buzz of excitement regarding the lack of new Cycle-24 sunspots. Could this solar minimum turn into another extended solar minimum, with possible consequences for the terrestrial climate? Or is it too early to be sure? Our workshop dealt with this question in some detail. The consensus opinion (opinions count here, since there is no workable theory of the solar cycle) holds that it is too soon to panic. We illustrate this with Figure 1, which uses