Haruhisa Iijima (Nagoya University)
The predicting the 11-year sunspot cycle is an important task for the long-term prediction of the space weather.
One successful method to predict the next solar cycle is the precursor method, which uses the high correlation between the polar field strength at the solar cycle minimum and the maximum sunspot number in the next cycle.
We extend the precursor method by predicting the polar field formation using the Surface Flux Transport model (SFT model). In this study, we carefully compare the prediction by the SFT model and the solar surface magnetic field observed by Wilcox Solar Observatory, Solar and Heliospheric Observatory, and Solar Dynamic Observatory.
We find that the new sunspot emergence rarely contributes to the polar field formation near the end of each solar sunspot cycle minimum. This observational characteristics allows us to predict the polar field strength without the detailed modeling of the new sunspot emergence in the model. According to our prediction scheme, the maximum sunspot number in the next solar cycle will be 10–20 % smaller than that in the current cycle.
Iijima, H., Hotta, H., Imada, S., Kusano, K., and Shiota, D. (2017), Improvement of solar-cycle prediction: Plateau of solar axial dipole moment, Astronomy & Astrophysics, 607, L2
DOI: 10.1051/0004-6361/201731813
https://www.aanda.org/articles/aa/abs/2017/11/aa31813-17/aa31813-17.html
Fig. 1 : Time evolution of the observed polar field indicator (axial dipole moment; thick lines)
Fig. 2 : Prediction of the maximum sunspot number in the Cycle N compared with the strength of the polar field indicator at the activity minimum in the Cycle N-1.