The strongest geomagnetic storm from the sun in two decades left the electricity grid unaffected, but disrupted Ordnance Survey (OS) monitors used to provide accurate data about the location of Great Britain (GB).
Space weather “is caused by disturbances from active regions of The Sun”.
It is a normal part of activity within the solar system, and the most visible daily impacts on Earth are the aurora borealis around the North Pole and the aurora australis around the south pole.
Extreme space weather expected to peak in 2025
Severe space weather, however according to a report published earlier this year, “poses a hazard to critical national infrastructure including space-based services such as global navigation satellite systems (GNSS) and satellite communications”.
It can also impact systems in the atmosphere like aircraft electronics, and ground-based systems like power grids and mobile cellular networks”.
NCE revealed earlier in August 2025 that 2025 is expected to see the most notifications issued ever by the Met Office Space Weather Operations Centre (Moswoc) to critical national infrastructure managers, according to data released via the Freedom of Information Act.
National Grid unaffected by worst geomagnetic storm of two decades
It can also now be reported that when the country was hit by “notable period of space weather” in May 2024, the geomagnetic storm which was caused by the interaction of the space weather with the Earth’s atmosphere “was declared by the Met Office as the strongest of its type in two decades,” according to OS, GB’s national mapping service.
The storm “caused temporary disruption to satellite communications, GPS signals and radio communications, but stopped short of affecting the National Grid,” OS said.
“OS Net base stations were affected – they were unable to provide centimetre-level positioning for one hour. Lower levels of disruption were also observed throughout the remainder of the weekend.
“These impacts have been fed back to national and international forums to help deepen understanding of what impacts more severe space weather events could bring.”
Ground-based positioning monitors supporting Met Office forecasting
OS shared the revelations as it highlighted its work with the Met Office.
It said it had been sharing the outputs of its network of ground-based global navigation satellite systems (GNSS), known as OS Net, to support the Met Office’s space weather forecasting.
The most high-profile GNSS system in the UK is the Global Positioning System (GPS), which is space-based and owned by the US Department of Defense. GNSS are a type of positioning, navigation and timing (PNT) service.
Unusually, OS’s GNSS system is based on Earth and is able to identify changes to each units locations to the nearest 1cm. Movements of the surface are possible due to tectonic movements and isostatic shift, where land moves as it settles on the softer magma below the crust.
OS explained that PNT services “which are used to facilitate many core functions across our society – can be affected by space weather, from operating our phones, satnavs and online maps, to the navigation systems relied upon by airplanes, ships and trains.
“Disruption could also include impacts to some ground-based infrastructure, including power grids and utilities.
“Therefore Critical National infrastructure (CNI) providers – which are dependent upon GNSS for timing services – need to understand the impact and mitigate the effect that space weather has upon GNSS based systems.
“The cost to the UK economy of just a few days of disruption could be billions of pounds – one reason why space weather is recognised on the National Risk Register.”
It went on to say that OS Net has “defined Great Britain’s coordinate reference system (including its position on Earth) and provides GNSS corrections, enabling access to 1cm real time positioning for OS surveyors and partners.”
The data from the OS Net is “constantly monitored and analysed for disruption, such as from solar storms,” OS said.
“This information is invaluable and is used to help validate and drive Met Office space weather forecasts, along with data from other partners such as British Geological Survey – with these forecasts helping organisations mitigate potential disruption.”
OS lead scientist (PNT) Steve Hancock said: “Ordnance Survey has been defining position within Great Britain for over 230 years, and is now providing highly accurate measurements using our nationwide network of high performance GNSS receivers.
“As technology evolves, so do the demands placed upon all of us and for OS this means that we continue to explore the development of PNT technologies, systems and services.
“Today, the demand for resilient PNT has never been more important, and we must work together to provide a whole system approach to PNT to preserve national security and public safety.”
Met Office space weather manager Krista Hammond said: “Space weather forecasting is reliant on observations to help inform future forecasts.
“With sparse data availability when compared to meteorology, every bit of information that can be gathered is useful in not only informing the current space weather forecast, but also for developing our understanding of what to expect in severe space weather events.
“Data from Ordnance Survey, and that from other partners, is a vital part of the forecasting chain and helps inform the long-term resilience of the UK to severe space weather events.”
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