Scientists have developed a new way to predict the strength of the Sun's next activity cycle up to seven years before it reaches its peak.
The new method uses the number of sunspots at a newly-identified 'switch-off' point in the solar cycle, when the Sun's most extreme space weather suddenly comes to an end. Using this approach, researchers have made an early prediction for the strength of Solar Cycle 26.
A very early prediction shows a moderate Cycle 26 with a sunspot number of around 100-120, similar to or weaker than the current Cycle 25. However, exact predictions won't be possible for another two years, and a weaker or stronger cycle are both still theoretically possible.
The research is being presented this week at the Royal Astronomical Society's National Astronomy Meeting in Birmingham .
Sandra Chapman, Professor of Physics and Director of the Centre for Fusion, Space and Astrophysics at the University of Warwick, said: "The Sun doesn't gently go to sleep and then gently wake up again.
"Instead, we've discovered that the most extreme space weather switches off quite suddenly at a specific point in every solar cycle. By identifying that point, we've found a new way to predict how active the next solar cycle is likely to be."
Professor Chapman expects to refine the prediction in around two years, once Solar Cycle 25 reaches the newly-identified 'switch-off' point and the forecast can be based on observations rather than projections.
The Sun follows an approximately 11-year cycle during which its magnetic field reverses polarity, and the number of sunspots rises and falls. Sunspots are regions of intense magnetic activity that can produce powerful solar flares and coronal mass ejections, creating space weather that can affect satellites, communications, navigation systems and power grids on Earth.
Although astronomers have monitored sunspots for centuries, no two solar cycles are exactly the same. They vary in both length and intensity, making it difficult to predict how active the next cycle will be.
The new prediction method builds on Professor Chapman's previously developed 'sunclock', which maps the Sun's irregular cycles onto a standard clock. This revealed that the most extreme space weather does not gradually fade away but instead switches off at a distinct point in each solar cycle.
Professor Chapman's team has found that the number of sunspots present at this switch-off point is closely linked to the peak number of sunspots in the following solar cycle. This provides a new forecasting method that can predict the strength of the next solar cycle around six to seven years before it reaches its maximum, giving a longer lead time than current methods, which rely on waiting until the solar minimum.
The new method also identifies a specific stage in the solar cycle when the magnetic field that drives the next cycle should become established. The research team hopes this will help improve understanding of the solar dynamo, the process that generates the Sun's magnetic field.
Professor Chapman said: "We're about two years away from the switch-off point for the current Solar Cycle 25. 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."
The method successfully predicted that Solar Cycle 25 would be stronger than many previous forecasts suggested, resulting in the stunning displays of aurora in recent years.
The UK experienced several historic solar storms in 2024 as Cycle 25 reached its 'solar maximum', most notably a series of extreme geomagnetic events from 10 to 13 May.
Triggered by a cluster of massive sunspots approaching solar maximum, these events produced the most powerful geomagnetic storms to impact Earth in over two decades. These resulted in widespread, vivid auroral displays across the UK, with northern lights seen as far south as Devon and Cornwall.
In 2022, Professor Chapman was awarded the Royal Astronomical Society's Chapman Medal for pioneering research that transformed astronomers' understanding of how planetary magnetic fields behave and produce space weather.
