Severe space weather

Impact 5
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upper likelihood error bar
risk indicator
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Impact & Likelihood
Impact key
5 Catastrophic
4 Significant
3 Moderate
2 Limited
1 Minor
Likelihood key
5 >25%
4 5-25%
3 1-5%
2 0.2-1%
1 <0.2%


The term ‘space weather’ describes a series of phenomena originating from the sun, which include solar flares, solar energetic particles and coronal mass ejections. Day-to-day space weather causes little more than the Aurora Borealis in polar regions, but strong space weather events can bring disruption to many vital technologies. Orbiting satellites are particularly vulnerable to space weather effects, and can be damaged or temporarily disabled.


The reasonable worst-case scenario for this risk is based on a severe space weather event, approximately the same scale and magnitude as the Carrington Storm of 1859, lasting for 1-2 weeks. It includes a number of different solar phenomena including coronal mass ejections, solar flares, solar radiation storms and solar radio bursts. Each phenomenon would likely occur several times during a 2-week period, with each varying in magnitude, temporal and spatial extent. Impacts may include regional power disruptions, loss or disruption of Global Navigation Satellite Systems (for example Global Positioning System - (GPS)) and some telecommunications (for example satellite communications and high-frequency radio), disruption to aviation, an increase in background radiation doses at high altitudes and in space, and possible disruption to ground-based digital components. The catalogue of tracked objects on-orbit would be significantly impacted, raising the risk of on-orbit collisions. There may also be second order impacts such as fatalities and casualties (for example, in the event of power disruptions).

Key assumptions

The impacts of severe space weather would be global, although the magnitude would vary, with the key dependencies being latitude, reliance on access to space for the operation of key services and the resilience of engineered and digital infrastructure.


Notable variations are possible in the timescale, type and magnitude of driving solar activity. Therefore, significant events with lesser or greater overall and/or differential impact spectra should be anticipated. This could lead to greater disruption in some sectors, such as aviation and the emergency services.

Response capability requirements

Mobile back-up power generation would be required in some areas for a sustained period, while damaged electricity transformers are replaced, which could take several months. Additionally, resilient communications systems and support for local emergency services and vulnerable members of these populations will be needed.


Loss of power due to safety system trips in urban areas could be recovered in a matter of hours. In the event of electricity transformers needing to be replaced in remote coastal areas, recovery could take several months based upon current replacement transformer availability. Loss of, or disruption to, satellite based services and Global Navigation Satellite Systems (for example GPS) has a recovery time of several days, with a small number of satellites non- recoverable. It could take weeks for flight schedules (especially long- haul carriers) to fully return to normal. The catalogue of tracked objects on-orbit (satellites and debris) could similarly take weeks to re-establish, with this temporarily raising the risk of collisions.