Solar Cycle Prediction

Abstract

A review of solar cycle prediction methods and their performance is given, including forecasts for cycle 24. The review focuses on those aspects of the solar cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming solar maximum no later than right after the start of the given cycle.Prediction methods form three main groups. Precursor methods rely on the value of some measure of solar activity or magnetism at a specified time to predict the amplitude of the following solar maximum. Their implicit assumption is that each numbered solar cycle is a consistent unit in itself, while solar activity seems to consist of a series of much less tightly intercorrelated individual cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variations are the same at any point of time and, therefore, it lends itself to analysis and forecasting by time series methods. Finally, instead of an analysis of observational data alone, model based predictions use physically (more or less) consistent dynamo models in their attempts to predict solar activity.In their overall performance during the course of the last few solar cycles, precursor methods have clearly been superior to extrapolation methods. Nevertheless, most precursor methods overpredicted cycle 23, while some extrapolation methods may still be worth further study. Model based forecasts have not yet had a chance to prove their skills. One method that has yielded predictions consistently in the right range during the past few solar cycles is that of K. Schatten et al., whose approach is mainly based on the polar field precursor.The incipient cycle 24 will probably mark the end of the Modern Maximum, with the Sun switching to a state of less strong activity. It will therefore be an important testbed for cycle prediction methods and, by inference, for our understanding of the solar dynamo.

Horizontal flow fields observed in Hinode G-band images

“…The present study can consequently be considered as an extension of these studies that focuses on a much quieter magnetic field topology, which might be representative of the lower solar activity during cycle No. 24 (Petrovay 2010;Nielsen & Kjeldsen 2011).…”

Solar forcing for CMIP6 (v3.2)

“…The solar-cycle averaged modulation potential (and the sunspot number) cannot be meaningfully predicted more than a few solar cycles ahead (e.g., Kremliovsky, 1995;Petrovay, 2010). Thus, whatever is discussed further is only a plausible scenario that is not pretending to be a prediction with any degree of confidence.…”

“…Ever since the solar cycle was first observed, people have been trying to predict what future cycles may look like. Prediction methods were empirical, and at best could give some clue of what the amplitude of the next cycle could be (Petrovay, 2010). This situation prevailed until the early 21st century, when physical models of the magnetic dynamo that drives solar activity started unveiling a more realistic picture (Charbonneau, 2010).…”

Does Correction Factor Vary with Solar Cycle?

“…This is why the international scientific community has continuously renewed its interest in the sunspot number. Many scientific investigations, including cycle analysis and forecast, solar North-South asymmetry analysis, coherence analysis of the solar magnetic field, mid-term studies of solar activity, are based on the Solar Influences Data Analysis Center (SIDC) sunspot data (Pulkkinen et al 1999, Lockwood 2003, Solanki et al 2004, Wang 2004, Chang 2007, Usoskin 2008, Petrovay 2010, Ternullo 2010, Kim & Chang 2011.…”