Solar cycle 25
The beginning date of Solar cycle 25 is yet to be determined; when extensive recording of solar sunspot activity began. Its most likely start date is December 2019, but as this is based on a 13-month running mean of sunspot numbers, this cannot be certified until late 2020. It is expected to continue until 2030.
Predictions
The Solar Cycle 25 Prediction Panel predicted in December 2019 that Solar Cycle 25 will be similar to Solar Cycle 24, with the preceding Solar Cycle minimum in April 2020 ; the solar maximum smoothed sunspot number of 115 in July 2025. This prediction is in line with the current general agreement in the scientific literature, which holds that solar cycle 25 will be weaker than average. Upton and Hathaway have predicted that the weakness of cycle 25 would make it part of the Modern Gleissberg Minimum.Several varying predictions have been made regarding the strength of cycle 25, with predictions ranging from very weak with suggestions of slow slide in to a Maunder minimum like state to a weak cycle similar to previous cycle 24 and even a strong cycle. One published solar cycle prediction, which had claimed a very weak cycle with a slide to Maunder-like minimum in activity, was retracted, with the agreement of one of its four authors, by the Editors of Nature due to fundamental errors which overstated Earth-Sun distance variability over a period of centuries.
| Source | Date | Cycle max | Cycle start | Cycle end |
| Thompson, M.J. et al. | August 2014 | Q4 2019 | ||
| Zharkova, V. et al 2014, 2015. | October 2014, | 80% of cycle 24 | ||
| Upton, L.A. and Hathaway, D.H. | December 2018 | 95% of cycle 24 | Late 2020 – Early 2021 | |
| Xu, J.C. et al. | August 2018 | 152.2–184.8 | October 2020 | |
| Bhowmik, P. and Nandy, D. | December 2018 | 109–139 | 2020 | after 2031 |
| Ozguc, A. et al. | December 2018 | 154±12 | ||
| NOAA / SSRC | April 2019 | 95–130 | mid-2019 – late 2020 | |
| NASA | June 2019 | 30–50% lower than Cycle 24 | 2020 | |
| NOAA / SSRC | December 2019 | 105–125 | April 2020 |
Early signs
As at April 2018, the Sun showed signs of a reverse magnetic polarity sunspot appearing and beginning this solar cycle. It is typical during the transition from one cycle to the next to experience a period where sunspots of both polarities exist. The polarward reversed polarity sunspots suggest that a transition to cycle 25 is in process. The first Cycle 25 sunspot may have appeared in early April 2018 or even December 2016.In November 2019, two reversed polarity sunspots appeared, possibly signaling the onset of cycle 25.
Nandy et al. analyzed the polarity orientation of bipolar magnetic regions observed in December 2019 and concluded that magnetic regions with the underlying orientation of solar cycle 25 toroidal field component were brewing in the solar convection zone, representing early signs of the new cycle.