Solar cycle 25

Solar cycle 25 is the current, and 25th solar cycle since 1755, when extensive recording of solar sunspot activity began.[1][2] 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.[3][4]

Predictions

The Solar Cycle 25 Prediction Panel predicted in December 2019[5] that Solar Cycle 25 will be similar to Solar Cycle 24, with the preceding Solar Cycle minimum in April 2020 (plus/minus six months); the solar maximum smoothed sunspot number of 115 in July 2025 (plus/minus 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).[6] Upton and Hathaway have predicted that the weakness of cycle 25 would make it part of the Modern Gleissberg Minimum.[7]

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[8][7][9] to a weak cycle similar to previous cycle 24[6] and even a strong cycle.[10][11] 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published solar cycle prediction, which had claimed a very weak cycle with a slide to Maunder-like minimum in activity, was retracted, with the agreement of one of its four authors, by the Editors of Nature due to fundamental errors which overstated Earth-Sun distance variability over a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.[8]

Cycle 25 predictions
Source Date Cycle max Cycle start Cycle end
Thompson, M.J. et al.[4] 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.[7] (Solar Observatories Group, Stanford University) December 2018 95% of cycle 24 Late 2020 – Early 2021
Xu, J.C. et al.[10] (Chinese Academy of Sciences) August 2018 152.2–184.8 (2024) October 2020
Bhowmik, P. and Nandy, D.[6] (IISER Kolkata) December 2018 109–139 (2023–2025) 2020 after 2031
Ozguc, A. et al.[11] (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)

Early signs

As at April 2018, the Sun showed signs of a reverse magnetic polarity sunspot appearing and beginning this solar cycle.[16] 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.[17] The first Cycle 25 sunspot may have appeared in early April 2018[18][19] or even December 2016.[17]

In November 2019, two reversed polarity sunspots appeared, possibly signaling the onset of cycle 25.[20][21]

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.[22]

References
  1. Kane, R.P. (2002). "Some implications using the Group Sunspot Number reconstruction". Solar Physics. 205 (2): 383–401. Bibcode:2002SoPh..205..383K. doi:10.1023/A:1014296529097.
  2. "The Sun: Did you say the Sun has spots?". Space Today Online. Retrieved 12 August 2010.
  3. Odenwald, Sten (2 September 2016). "Waiting for the next sunspot cycle: 2019-2030". The Huffington Post. Retrieved 22 November 2017.
  4. 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.
  5. "Solar Cycle 25 Forecast Update | NOAA / NWS Space Weather Prediction Center".
  6. 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.
  7. 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. doi:10.1029/2018GL078387.
  8. 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.
  9. Kitiashvili et al.
  10. 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.
  11. 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.
  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. "Coronal hole faces Earth". Space Weather Live. Retrieved 24 April 2018.
  17. Phillips, Tony (20 November 2018). "A sunspot from the next solar cycle". SpaceWeather.com. Retrieved 13 December 2018.
  18. "Cycle 25 observations in SDO HMI imagery". Retrieved 2018-05-04.
  19. Hudson, Hugh (10 April 2018). "A sunspot from cycle 25 for sure". RHESSI project. Retrieved 22 November 2018.
  20. "www.nso.edu Do we see a dawn of solar cycle 25?". www.nso.edu/blog. 25 November 2019. Retrieved 2019-11-26.
  21. "Spaceweather.com Time Machine". spaceweather.com. Retrieved 2019-12-26.
  22. 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.
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