Solar cycle 25

Widely varying predictions regarding the strength of cycle 25 ranged from very weak with suggestions of slow slide in to a Maunder minimum like state[5][6] to a weak cycle similar to previous cycle 24[7] and even a strong cycle.[8][9][10] Upton and Hathaway predicted that the weakness of cycle 25 would make it part of the Modern Gleissberg Minimum.[5]

The Solar Cycle 25 Prediction Panel predicted in December 2019[11] that solar cycle 25 will be similar to solar cycle 24, with the preceding solar cycle minimum in April 2020 (± 6 months), and the number of sunspots reaching a (smoothed) maximum of 115 in July 2025 (± 8 months). 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 (i.e. weaker than during the exceptionally strong Modern Maximum).[7] However, observations from 2020 to 2022, the first three years of the cycle, significantly exceed predicted values.[12]

Time vs. solar latitude diagram of the radial component of the solar magnetic field (supersynoptic map or “butterfly” diagram) for cycle 24 based on the (zero-point corrected) integer rotation synoptic maps from GONG. Blue/red show negative/positive polarity fields scaled between ±5 Gauss. Two black arrows mark approximate location of two latitudinal bands of cycle 25. Data are acquired by GONG instruments operated by NISP/NSO/AURA/NSF.

As of April 2018, the Sun showed signs of a reverse magnetic polarity sunspot appearing and beginning this solar cycle.[20] It is typical during the transition from one cycle to the next to experience a period where sunspots of both polarities exist (during the solar minimum). The polarward reversed polarity sunspots suggested that a transition to cycle 25 was in process.[21] The first cycle 25 sunspot may have appeared in early April 2018[22][23] or even December 2016.[21]

In November 2019, two reversed polarity sunspots appeared, possibly signaling the onset of cycle 25.[24][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.[26]

Supersynoptic (time vs. solar latitude) map of the radial component of the solar magnetic field for cycles 24-25 based on observations from the Global Oscillations Network Group (GONG) shows magnetic activity of cycle 25 beginning November 2019 at about 30 degree latitudes in both solar hemispheres.[27] A more recent supersynoptic map is available.[28]

The following table gives the number of days so far in cycle 25 against the number up to the same point in cycle 24, and also up to the end of 2012 in cycle 24, which have passed various thresholds for the numbers of sunspots.

As at Sep 22 2023, solar cycle 25 is averaging 25% more spots per day than solar cycle 24 at the same point in the cycle (Sep 22 2012).
Year 4 of solar cycle 25 (Dec 1 2022 to Sep 22 2023) is averaging 45% more spots per day than the corresponding period in solar cycle 24.

• Active region

• "Solar Cycle Prediction". NASA Marshall Space Flight Center.
• "Solar Cycle Progression". NOAA Space Weather Prediction Center.
• "Solar Cycle Prediction". Solar Cycle Science.