Solar cycle 25

Solar cycle 25 is the current solar cycle pattern of sunspot activity. It began in December 2019, with a smoothed minimum sunspot number of 1.8.[1] It is expected to continue until about 2030.[2][3]

Predictions

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[4][5][6] to a weak cycle similar to previous cycle 24[7] and even a strong cycle.[8][9][10] 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published solar cycle prediction, which had claimed a very weak cycle with a slide to Maunder-like minimum in activity, was retracted, with the agreement of one of its four authors, by the Editors of Nature due to fundamental errors which overstated Earth-Sun distance variability over a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.[4] Upton and Hathaway have 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]

Cycle 25 predictions
Source Date Cycle max Cycle start Cycle end
Thompson, M.J. et al.[3] August 2014 Q4 2019
Zharkova, V. et al 2014, 2015.[12] (Northumbria U.) October 2014, 80% of cycle 24
Upton, L.A. and Hathaway, D.H.[5] (Solar Observatories Group, Stanford University) December 2018 95% of cycle 24 Late 2020 – Early 2021
Xu, J.C. et al.[8] (Chinese Academy of Sciences) August 2018 152.2–184.8 (2024) October 2020
Bhowmik, P. and Nandy, D.[7] (IISER Kolkata) December 2018 109–139 (2023–2025) 2020 after 2031
Ozguc, A. et al.[9] (Harvard U-ty) December 2018 154±12 (2023.2±1.1)
NOAA / SSRC[13] April 2019 95–130 (2023–2026) mid-2019 – late 2020
NASA[14] June 2019 30–50% lower than Cycle 24 (2025) 2020
NOAA / SSRC (update)[15] December 2019 105–125 (July 2025) April 2020 (+/- 6 months)
National Center for Atmospheric Research[16] December 2020 233

Early signs
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.[17] 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 suggest that a transition to cycle 25 is in process.[18] The first Cycle 25 sunspot may have appeared in early April 2018[19][20] or even December 2016.[18]

In November 2019, two reversed polarity sunspots appeared, possibly signaling the onset of cycle 25.[21][22]

Nandy et al. (2020, Res. Notes of the AAS) 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.[23]

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.[24]

As at January 1, 2021, solar cycle 25 is showing early signs of being somewhat stronger than solar cycle 24.
• The 13-month average sunspot count for June 2020 was 7.8 spots per day, compared to 4.1 for the corresponding month in the previous cycle.
• November 2020 averaged 34 spots per day, 10 months earlier than the first month to average 30 or more in cycle 24.
• The first single day to have 90 spots has occurred in month 12 of this cycle, compared with month 27 in cycle 24.
• Since June 1, 2020, there have been 80 spotless days, compared to 139 in the corresponding period of cycle 24.[25]
• 2020 had 80% more sunspots than for the corresponding period in SC24. These figures are in early agreement with a new paper (October 2020) by McIntosh et. al.[26] which projects that solar cycle 25 will almost certainly be stronger than SC24 (ISN max 116), and most likely stronger than SC23 (ISN max 180).

Events

2020
Solar flares in 2020[27]
10
20
30
40
50
60
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
  •   C
  •   M
  •   X

On 29 May, the first C-class solar flares of Solar Cycle 25 took place, including the first M-class flare. Solar activity continued to increase in the following months, especially abruptly in October, with flares taking place on a near-daily basis by November. On November 29, an M4.4 flare, the strongest of the cycle to date, took place, possibly indicating the Solar Cycle would be more active than initially thought.[28]

On 8 December, a small coronal mass ejection was found heading directly towards Earth shortly after a strong C-class solar flare, hitting the planet on 9/10 December and causing bright aurorae at high latitudes.[29][30]

References
  1. National Weather Service. "Hello Solar Cycle 25". Retrieved 15 September 2020.
  2. Odenwald, Sten (2 September 2016). "Waiting for the next sunspot cycle: 2019-2030". The Huffington Post. Retrieved 22 November 2017.
  3. McIntosh, Scott W.; Wang, Xin; Leamon, Robert J.; Davey, Alisdair R.; Howe, Rachel; Krista, Larisza D.; Malanushenko, Anna V.; Markel, Robert S.; Cirtain, Jonathan W.; Gurman, Joseph B.; Pesnell, William D.; Thompson, Michael J. (8 August 2014). "Deciphering Solar magnetic activity: On the relationship between the sunspot cycle and the evolution of small magnetic features". The Astrophysical Journal. 792 (1): 12. arXiv:1403.3071. Bibcode:2014ApJ...792...12M. doi:10.1088/0004-637X/792/1/12. S2CID 118418019.
  4. Zharkova, V. V.; Shepherd, S. J.; Zharkov, S. I.; Popova, E. (4 March 2020). "Retraction Note: Oscillations of the baseline of solar magnetic field and solar irradiance on a millennial timescale". Scientific Reports. 10 (1): 4336. Bibcode:2020NatSR..10.4336Z. doi:10.1038/s41598-020-61020-3. PMC 7055216. PMID 32132618.
  5. Upton, Lisa A.; Hathaway, David H. (28 August 2018). "An updated solar cycle 25 prediction with AFT: The modern minimum". Geophysical Research Letters. 45 (16): 8091–8095. arXiv:1808.04868. Bibcode:2018GeoRL..45.8091U. doi:10.1029/2018GL078387. S2CID 118913702.
  6. Kitiashvili et al.
  7. Bhowmik, Prantika; Nandy, Dibyendu (6 December 2018). "Prediction of the strength and timing of sunspot cycle 25 reveal decadal-scale space environmental conditions". Nature Communications. 9 (1): 5209. arXiv:1909.04537. Bibcode:2018NatCo...9.5209B. doi:10.1038/s41467-018-07690-0. PMC 6283837. PMID 30523260.
  8. Li, F.Y.; Kong, D.F.; Xie, J.L.; Xiang, N.B.; Xu, J.C. (December 2018). "Solar cycle characteristics and their application in the prediction of cycle 25". Journal of Atmospheric and Solar-Terrestrial Physics. 181: 110–115. Bibcode:2018JASTP.181..110L. doi:10.1016/j.jastp.2018.10.014.
  9. Sarp, V; Kilcik, A; Yurchyshyn, V; Rozelot, J P; Ozguc, A (December 2018). "Prediction of solar cycle 25: a non-linear approach". Monthly Notices of the Royal Astronomical Society. 481 (3): 2981–2985. Bibcode:2018MNRAS.481.2981S. doi:10.1093/mnras/sty2470.
  10. McIntosh, Scott W.; Chapman, Sandra C.; Leamon, Robert J.; Egeland, Ricky; Watkins, Nicholas W. (2020-06-26). "Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude". Solar Physics. 295 (12): 163. arXiv:2006.15263. Bibcode:2020SoPh..295..163M. doi:10.1007/s11207-020-01723-y. S2CID 220250556.
  11. "Solar Cycle 25 Forecast Update | NOAA / NWS Space Weather Prediction Center".
  12. Shepherd, Simon J.; Zharkov, Sergei I.; Zharkova, Valentina V. (13 October 2014). "Prediction of solar activity from solar background magnetic field variations in cycles 21–23". The Astrophysical Journal. 795 (1): 46. Bibcode:2014ApJ...795...46S. doi:10.1088/0004-637X/795/1/46. hdl:10454/10790.
  13. "Scientists predict a new solar cycle is about to begin and that it might be stronger than the last one". Washington Post. 11 April 2019.
  14. "Solar activity forecast for next decade favorable for exploration". NASA Ames. 12 June 2019.
  15. "SOLAR CYCLE 25 FORECAST UPDATE". SPACE WEATHER PREDICTION CENTER - NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION. 9 December 2019.
  16. "Maverick astrophysicist calls for unusually intense solar cycle, straying from consensus view". The Washington Post. 19 December 2020.
  17. "Coronal hole faces Earth". Space Weather Live. Retrieved 24 April 2018.
  18. Phillips, Tony (20 November 2018). "A sunspot from the next solar cycle". SpaceWeather.com. Retrieved 13 December 2018.
  19. "Cycle 25 observations in SDO HMI imagery". Retrieved 2018-05-04.
  20. Hudson, Hugh (10 April 2018). "A sunspot from cycle 25 for sure". RHESSI project. Retrieved 22 November 2018.
  21. "www.nso.edu Do we see a dawn of solar cycle 25?". www.nso.edu/blog. 25 November 2019. Retrieved 2019-11-26.
  22. "Spaceweather.com Time Machine". spaceweather.com. Retrieved 2019-12-26.
  23. Nandy, Dibyendu; Bhatnagar, Aditi; Pal, Sanchita (2 March 2020). "Sunspot Cycle 25 is Brewing: Early Signs Herald its Onset". Research Notes of the AAS. 4 (2): 30. Bibcode:2020RNAAS...4...30N. doi:10.3847/2515-5172/ab79a1.
  24. Pevtsov, Alexei (17 October 2020). "Time vs. solar latitude diagram of the radial component of the solar magnetic field (supersynoptic map of "butterfly" diagram". Retrieved 2020-10-17.
  25. http://www.sidc.be/silso/datafiles
  26. McIntosh, Scott W.; Chapman, Sandra; Leamon, Robert J.; Egeland, Ricky; Watkins, Nicholas W. (2020). "Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude" (PDF). Solar Physics. 295 (12): 163. arXiv:2006.15263. Bibcode:2020SoPh..295..163M. doi:10.1007/s11207-020-01723-y. S2CID 220250556.
  27. "Aurora and solar activity archive". spaceweatherlive. Retrieved 10 December 2020.
  28. "M4.44 solar flare". www.spaceweatherlive.com. spaceweatherlive. 29 November 2020. Retrieved 10 December 2020.
  29. "Earth-directed coronal mass ejection". www.spaceweatherlive.com. spaceweatherlive. Retrieved 10 December 2020.
  30. Meteorologist, Derek Van Dam, CNN (9 December 2020). "Sun launches explosion of electromagnetic energy towards Earth: Geomagnetic Storm Watch issued". CNN. CNN. Retrieved 10 December 2020.
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