On the Strength and Duration of Solar Cycle 25: A Novel Quantile-Based Superposed-Epoch Analysis

Abstract

The sunspot number (SSN) is an important – albeit nuanced – parameter that can be used as an indirect measure of solar activity. Predictions of upcoming active intervals, including the peak and timing of solar maximum, can have important implications for space weather planning. Forecasts for the strength of Solar Cycle 25 have varied considerably, from being very weak to one of the strongest cycles in recorded history. In this study, we develop a novel quantile-based superposed-epoch analysis that currently predicts that Solar Cycle 25 will be very modest (within the lowest 25th percentile of all numbered cycles), with a monthly-averaged (13-month average) peak of ≈ 130 (110) likely occurring in December 2024. We validate the model by performing retrospective forecasts (hindcasts) for the previous 24 cycles, finding that it outperforms the baseline (reference) model (the “average cycle”) 75% of the time.