The polar precursor method for solar cycle prediction: comparison of predictors and their temporal range

Abstract

The polar precursor method is widely considered to be the most robust physically motivated method to predict the amplitude of an upcoming solar cycle.It uses indicators of the magnetic field concentrated near the poles around sunspot minimum. Here, we present an extensive performance analysis of various such predictors, based on both observational data (WSO magnetograms, MWO polar faculae counts and Pulkovo $A(t)$ index) and outputs (polar cap magnetic flux and global dipole moment) of various existing flux transport dynamo models.We calculate Pearson correlation coefficients ($r$) of the predictors with the next cycle amplitude as a function of time measured from several solar cycle landmarks: setting $r=0.8$ as a lower limit for acceptable predictions, we find that observations and models alike indicate that the earliest time when the polar predictor can be safely used is 4 years after polar field reversal. This is typically 2--3 years before solar minimum and about 7~years before the predicted maximum, considerably extending the {usual} temporal scope of the polar precursor method. Re-evaluating the predictors another 3 years later, at the time of solar minimum, further increases the correlation level to $r\ga 0.9$. As an illustration of the result, we determine the predicted amplitude of Cycle 25 based on the value of the WSO polar field at the now official minimum date of December 2019 as $126\pm 3$. A forecast based on the value in early 2017, 4~years after polar reversal would have only differed from this final prediction by $3.1\pm 14.7$\%.

Accepted in ApJ; 13 pages,7 figures

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Cited by in corpus (14)

• Models for the long-term variations of solar activity
• Physical link of the polar field build-up with the Waldmeier effect broadens the scope of early solar cycle prediction: Cycle 25 is likely to be slightly stronger than Cycle 24
• Long-term Variations in Solar Activity: Predictions for Amplitude and North--South Asymmetry of Solar Cycle 25
• Role of observable nonlinearities in solar cycle modulation
• Dynamo Model for North-South Asymmetry of Solar Activity
• Supercriticality of the dynamo limits the memory of the polar field to one cycle
• Discovery of a relation between the decay rate of the Sun's magnetic dipole and the growth rate of the following sunspot cycle: a new precursor for solar cycle prediction
• Effects of Emerging Bipolar Magnetic Regions in Mean-field Dynamo Model of Solar Cycles 23 and 24
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• Maximal growth rate of the ascending phase of a sunspot cycle for predicting its amplitude
• Probing the variations in the timing of the Sun's polar magnetic field reversals through observations and surface flux transport simulations
• Role of sunspot latitude versus tilt in determining the polar field and amplitude of the next cycle: Cause of the weak Solar Cycle 20
• Solar Cycle Prediction: Challenges, Progress, and Future Perspectives
• Evolution of the Sun's activity and the poleward transport of remnant magnetic flux in Cycles 21--24