Predicting Solar Cycle 25 with an Ap/F10.7 Geomagnetic Precursor Pair

Abstract:

Long-term predictions of solar activity indices are used in orbital prediction and mission planning. We describe using an Ap/F10.7 geomagnetic precursor pair to predict the amplitude of the just-started Solar Cycle 25. The method is an evolution of an earlier algorithm that now removes the baseline solar activity cycle-by-cycle. A recurrence index is used to determine the timing of the precursor peak used in the prediction. Unlike previous times, when the recurrence index showed well-defined peaks during the decline from solar maxima, the recurrence index in the decline of Solar Cycle 24 increases rapidly after solar maximum in 2014 and remains at a large value until 2020. The effect of this on the timing of the precursor value will be examined. We conclude that Solar Cycle 25 will be no stronger than average and could be much weaker than average.