http://arxiv.org/abs/2305.06516
Sunspot Cycle 25 is now over 3 years past the cycle minimum of December 2019. At this point in the cycle, curve-fitting to the activity becomes reliable and now consistently indicates a maximum sunspot number of 135 +/- 10 – slightly larger than Cycle 24’s maximum of 116.4, but well below the average of 179. A geomagnetic precursor, the minimum in the aa-index, and the Sun’s magnetic precursors, the Sun’s polar field strength and its axial dipole moment at the time of minimum, are often used to predict the amplitude of the cycle at (or before) the onset of the cycle. We examine Cycle 25 predictions produced by these precursors. The geomagnetic precursor indicated a Cycle 25 slightly stronger that Cycle 24, with a maximum of 132 +/- 8. The Sun’s magnetic precursors indicated that Cycle 25 would be more similar to Cycle 24, with a maximum sunspot number of 120 +/- 10 or 114 +/- 15. Combining the curve-fitting results with the precursor predictions, we conclude that Cycle 25 will have a maximum smoothed sunspot number of 134 +/- 8 with maximum occurring late in the fall of 2024. Models for predicting the Sun’s magnetic field ahead of minimum, were generally successful at predicting the polar precursors years in advance. The fact that Sun’s magnetic precursors at cycle minimum were successfully predicted years before minimum and that the precursors are consistent with the size of Cycle 25 suggests that we can now reliably predict the solar cycle.
L. Upton and D. Hathaway
Fri, 12 May 23
8/53
Comments: 14 pages, 5 figures, manuscript submitted to JGR: Space Physics on 5/9/2023