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

• Published in: Geophysical research letters 2018-08, Vol.45 (16), p.8091-8095
• Main Authors: Upton, Lisa A., Hathaway, David H.
• Format: Article
• Language: English
• Subjects: advective flux transport; Amplitude; Amplitudes; Cycle 25; Fluctuations; Flux; Gleissberg; Magnetic field; Magnetic field configurations; Magnetic fields; Maunder Minimum; Predictions; Solar cycle; Solar magnetic field; Solar minimum; Solar observations; Southern Hemisphere; Strength; Sun; Transport; Uncertainty
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2018GL078387

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 two 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 2 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 that includes solar observations through January of 2018. Plain Language Summary After the exceptionally weak Solar Cycle 24 (SC24), there is considerable interest in accurately predicting the amplitude of the coming Solar Cycle 25 (SC25). In 2016, the Advective Flux Transport (AFT) Model was used to make such a prediction. We now have two additional years of solar data. Here we compare the results of the previous prediction to the observations that have since occurred. We then use the additional two years of data to create an updated prediction, with a much smaller uncertainty. We predict that SC25 will be about slightly smaller (∼95%) the strength of SC24, making it the weakest solar cycle in the last hundred years. We also predict that,like SC24, SC25 will be preceded by a long extended solar minimum. Finally, these results indicate that we are now in the midst of a Modern Gleissberg Minimum. Key Points Cycle 25 will be slightly weaker than Cycle 24, making it the weakest cycle in the last hundred years Weak cycles are preceded by long extended minima; we may not reach the Cycle 24/25 minimum until 2021 We are currently (beginning with Cy