An Updated Solar Cycle 25 Prediction with AFT: The Modern Minimum

TL;DR

This paper evaluates and updates the Solar Cycle 25 prediction made by the AFT model, confirming its accuracy over two years and refining the forecast with new observational data.

Contribution

The study assesses the 2016 AFT model prediction using two additional years of data and provides an updated forecast for Solar Cycle 25.

Findings

AFT prediction closely matched observed magnetic field evolution

Southern hemisphere magnetic field weakening and recovery occurred as predicted

Updated forecast indicates similar cycle strength to Cycle 24

Abstract

Over the last decade there has been mounting evidence that the strength of the Sun's polar magnetic fields during a solar cycle minimum is the best predictor of the amplitude of the next solar cycle. Surface flux transport models can be used to extend these predictions by evolving the Sun's surface magnetic field to obtain an earlier prediction for the strength of the polar fields, and thus the amplitude of the next cycle. In 2016, our Advective Flux Transport (AFT) model was used to do this, producing an early prediction for Solar Cycle 25. At that time, AFT predicted that Cycle 25 will be similar in strength to the Cycle 24, with an uncertainty of about 15% . AFT also predicted that the polar fields in the southern hemisphere would weaken in late 2016 and into 2017 before recovering. That AFT prediction was based on the magnetic field configuration at the end of January 2016. We now have 2 more years of observations. We examine the accuracy of the 2016 AFT prediction and find that the new observations track well with AFT's predictions for the last two years. We show that the southern relapse did in fact occur, though the timing was off by several months. We propose a possible cause for the southern relapse and discuss the reason for the offset in timing. Finally, we provide an updated AFT prediction for Solar Cycle 25 which includes solar observations through January of 2018.