Solar cycle 25: another moderate cycle?

TL;DR

This study uses surface flux transport simulations with random bipolar magnetic region sources to predict that solar cycle 25 will likely be moderate in strength, but with significant uncertainty due to source variability.

Contribution

It introduces a method combining flux transport simulations with empirical scatter to forecast cycle strength and quantifies the prediction uncertainty.

Findings

Predicted axial dipole moment around 2020 is 2.5±1.1 G.

Cycle 25 is expected to be moderate, similar to cycle 23.

Prediction uncertainty is large due to source property scatter.

Abstract

Surface flux transport simulations for the descending phase of cycle 24 using random sources (emerging bipolar magnetic regions) with empirically determined scatter of their properties provide a prediction of the axial dipole moment during the upcoming activity minimum together with a realistic uncertainty range. The expectation value for the dipole moment around 2020 $(2.5\pm1.1\,$G) is comparable to that observed at the end of cycle 23 (about $2\,$G). The empirical correlation between the dipole moment during solar minimum and the strength of the subsequent cycle thus suggests that cycle 25 will be of moderate amplitude, not much higher than that of the current cycle. However, the intrinsic uncertainty of such predictions resulting from the random scatter of the source properties is considerable and fundamentally limits the reliability with which such predictions can be made before activity minimum is reached.