Scientists have discovered a new way to predict how active the sun’s next solar cycle will be years before it reaches its peak.
The research suggests that the sun has a surprisingly sudden “switch-off” point, when its most intense space weather rapidly comes to an end instead of fading away gradually.
The findings, presented at the Royal Astronomical Society’s National Astronomy Meeting in Birmingham, could give scientists up to seven years of advance warning about future solar activity.
Such long-term forecasts are important because powerful solar storms can disrupt satellites, GPS systems, radio communications, and even electricity grids on Earth.
The sun follows a cycle that lasts about 11 years. During each cycle, the sun’s magnetic field flips, and the number of sunspots rises and falls. Sunspots are dark regions on the sun’s surface where magnetic activity is especially strong.
They can produce massive solar flares and coronal mass ejections, sending huge amounts of energy and charged particles into space.
When these particles reach Earth, they create space weather that can interfere with modern technology but also produce spectacular displays of the Northern and Southern Lights.
Although scientists have observed sunspots for hundreds of years, predicting the strength of each new solar cycle has remained difficult because every cycle behaves differently. Some are much more active than others, and their timing also varies.
Professor Sandra Chapman, a physicist at the University of Warwick, believes her team has found an important clue. Instead of the sun slowly becoming quiet, they found that the most extreme space weather suddenly stops at a specific point during every solar cycle.
Her team identified this point using a model called the “sunclock,” which maps the sun’s irregular activity onto a standard clock. By studying past cycles, they discovered that the number of sunspots present at this switch-off point closely matches the strength of the following solar cycle.
This means scientists can estimate how active the next cycle will be six to seven years before it reaches its maximum. Existing forecasting methods usually require waiting until the sun reaches its quietest period, known as the solar minimum, which provides much less warning.
Using the new method, the researchers have already made an early estimate for Solar Cycle 26. Based on current information, they expect it to be moderate, with a peak sunspot number of around 100 to 120.
That would make it similar to or slightly weaker than the current Solar Cycle 25. However, Chapman says this prediction is still preliminary because the current cycle has not yet reached its switch-off point. More accurate forecasts should become possible in about two years, once scientists can rely on direct observations instead of estimates.
The method has already shown promise. It successfully predicted that Solar Cycle 25 would be stronger than many earlier forecasts suggested.
As a result, the world experienced impressive auroras and several powerful geomagnetic storms, including the historic solar storms of May 2024, when the Northern Lights became visible much farther south than usual in the United Kingdom.
Beyond improving space weather forecasts, the discovery may also help scientists better understand the solar dynamo, the process inside the sun that generates its magnetic field. A clearer picture of this hidden mechanism could lead to more reliable predictions of solar activity for many years to come.
