Historically, solar forecasting requires predicting the strength of an upcoming solar cycle by waiting for the “solar minimum”, the quietest period between cycles.
However, Professor Chapman’s team discovered that severe space weather does not gradually fade away; it terminates abruptly.
The mechanism: Over the course of a cycle, sunspots migrate from high latitudes down toward the solar equator.
Next steps for Cycle 26 and solar forecastingWhile early projections indicate a moderate Cycle 26, researchers emphasise that an exact, observation-based forecast will be finalised in approximately two years when Solar Cycle 25 officially hits its switch-off point.
“At the moment, we have to estimate where that point will be, but once we reach it, we can use observations alone to make a much more precise prediction for Solar Cycle 26.
Astrophysicists have developed a novel forecasting technique that can predict the peak strength of the Sun’s activity cycle up to seven years in advance
To be presented at the Royal Astronomical Society’s National Astronomy Meeting in Birmingham, the method relies on measuring sunspots at a newly identified “switch-off” point—the exact moment in a solar cycle when the most severe space weather abruptly ends.
Led by Professor Sandra Chapman, Director of the Centre for Fusion, Space and Astrophysics at the University of Warwick, the team used the model to offer an early forecast for Solar Cycle 26, predicting a moderate cycle with a peak sunspot count between 100 and 120 (similar to or slightly weaker than the current Cycle 25).
The discovery of the “switch-off” point
The Sun operates on an approximately 11-year cycle marked by reversing magnetic fields and fluctuating sunspot numbers. These intense magnetic regions generate solar flares and coronal mass ejections (CMEs) that can disrupt satellites, power grids, and communications on Earth.
Historically, solar forecasting requires predicting the strength of an upcoming solar cycle by waiting for the “solar minimum”, the quietest period between cycles. However, Professor Chapman’s team discovered that severe space weather does not gradually fade away; it terminates abruptly.
The mechanism: Over the course of a cycle, sunspots migrate from high latitudes down toward the solar equator. When these active regions move below roughly 15 degrees solar latitude, the differential rotation that twists up magnetic fields and fuels extreme CMEs weakens into a co-rotating band.
The transition: At this exact latitude, extreme space storm activity “switches off,” transitioning the Sun into a calmer state driven by weaker, predictable solar winds rather than violent plasma bursts.
Longer lead times for Earth’s infrastructure
By demonstrating that the number of sunspots remaining at this “switch-off” moment directly correlates with the peak intensity of the next cycle, researchers can now forecast space weather 6 to 7 years before its maximum, providing significantly more lead time than legacy models.
The methodology previously proved its accuracy by correctly predicting that the current Solar Cycle 25 would be stronger than mainstream consensus models suggested, a prediction validated by the extreme geomagnetic storms and widespread auroras observed across the globe in May 2024.
Next steps for Cycle 26 and solar forecasting
While early projections indicate a moderate Cycle 26, researchers emphasise that an exact, observation-based forecast will be finalised in approximately two years when Solar Cycle 25 officially hits its switch-off point.
“The Sun doesn’t gently go to sleep and then gently wake up again,” said Professor Chapman. “At the moment, we have to estimate where that point will be, but once we reach it, we can use observations alone to make a much more precise prediction for Solar Cycle 26. That will still give us around seven years’ warning of how strong the cycle is likely to be.”
