Sunspots are regions of intense magnetic activity on the Sun's surface. The number of sunspots rises and falls over the Sun's approximately 11-year activity cycle and is one of the main ways astronomers track and predict solar activity. (Credit: NASA/SDO License type Attribution (CC BY 4.0))
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.
ENDS
Press Release Details
Media contacts
Sam Tonkin
Royal Astronomical Society
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Dr Robert Massey
Royal Astronomical Society
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Megan Eaves
Royal Astronomical Society
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Science contacts
Sandra Chapman
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Images and captions
Image 1: Sunspots are regions of intense magnetic activity on the Sun’s surface. The number of sunspots rises and falls over the Sun’s approximately 11-year activity cycle and is one of the main ways astronomers track and predict solar activity. Credit: NASA/SDO
Figure 2: The ‘sunclock’ maps the Sun’s irregular activity cycle onto a standard clock. The black spokes show extreme space weather events recorded at Earth. The new research identifies a distinct ‘switch-off’ point, after which the most severe space weather events largely disappear until the next solar cycle begins. Credit: S.C. Chapman
Figure 3: The sunclock (centre) alongside the changing latitudes of sunspot activity (orange). The new study shows that the number of sunspots at the ‘switch-off’ point, when active regions have migrated close to the solar equator, can be used to predict the strength of the next solar cycle. Credit: S.C. Chapman
Further information
The switch-off also coincides with active sunspot regions moving to below about 15 degrees solar latitude. Each cycle, sunspots create a ‘butterfly pattern’ in which they start at high latitudes and then move towards the solar equator. The Sun has differential rotation – rotating at different speeds at different latitudes – but below about 15 degrees latitude, this differential rotation weakens, so that there is a co-rotating band at the solar equator (the solar ‘jet stream’). Professor Chapman believes that the coronal mass ejections that cause the most extreme space weather are powered by differential rotation twisting up the emerging magnetic field. This driver switches off once the sunspot active regions move to within 15 degrees. As a check, she looked at the 27-day (average solar rotation) correlation in the aa index (geomagnetic activity at Earth) and correlated that with space weather events. After the switch-off, the storms were less extreme, and they corresponded to a 27-day correlation, so are likely driven by co-rotating streams, not coronal mass ejections.
The talk ‘A new declining phase precursor to predict the next solar maximum sunspot number’ will take place at NAM2026 at 10:15 BST on Monday 20 July 2026 in room TLC118/119. Find out more at: https://uobevents-national-astronomy-meeting-2026.eventsairsite.com/block-schedule. If you would like a Zoom link to watch it online, please email [email protected]
Notes for editors
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