To understand the solar cycle, notice how the sun sleeps

Images from the Solar Dynamics Observatory highlight the appearance of the Sun at solar minimum (left, Dec. 2019) versus solar maximum (right, May 2024). The sun's activity follows an 11-year cycle, but predicting its exact timing and intensity remains challenging. A new study by Sandra Chapman found that solar maxima have a sharp cutoff point, where the number of sunspots drops significantly, and this correlates with the strength of the next solar maximum. The cutoff point also weakly correlates with the overall strength of a maximum. The sun is currently in Cycle 25, which is past its peak and will continue to decline in activity until around 2030. Based on observations so far, Cycle 26 is expected to be somewhat weaker than Cycle 25. The real test will come when the sun reaches its next switch-off point, which is predicted to occur in 2028.

• The study provides a new method for predicting solar cycle strength, based on the sharp cutoff point of sunspots.
• The cutoff point weakly correlates with the overall strength of a maximum but strongly correlates with the strength of the next maximum.
• Cycle 25 is past its peak and will continue to decline in activity until around 2030.
• The prediction for Cycle 26 is that it will be somewhat weaker than Cycle 25.
• The accuracy of the prediction will be tested when the sun reaches its next switch-off point, expected in 2028.

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