Predicting the Solar Cycle

Leif Svalgaard (Stanford)

The Solar Cycle 24 Prediction Panel received and evaluated ~75 prediction papers with predicted sunspot number maxima ranging from 40 to 200 and with a near normal distribution around the climatological mean indicative of the poor State of the Art. Flux Transport Dynamo Models were recently hoped to promise significant progress, but seem to have failed in their current form. In these models, higher meridional flow speed should produce strong polar fields and a short solar cycle, contrary to the observed behavior of increased meridional flow speed, low polar fields, and long-duration cycle 23. Poorly understood Precursor-methods again seem to work as for previous cycles. I review the current status of these methods. Predictions are usually expressed in terms of maximum Sunspot Number or maximum F10.7 radio flux, with the implicit assumption that there is a fixed [and good] relation between these measures of solar activity. If Livingston & Pennís observations of a secular change in sunspot contrast hold up, it becomes an issue which of these two measures of solar activity should be predicted and what it all means. The coming cycle 24 may challenge cherished and long-held beliefs and paradigms.

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