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