A space weather super-storm big enough to significantly disrupt electronic systems has occurred on average once in every 25 years, according to a new study.
By analysing magnetic field records at opposite ends of the Earth – in the UK and Australia – scientists have been able to detect super-storms going back over the last 150 years.
The findings come as the result of a new method of analysing historical data from the last 14 solar cycles, instead of the last five solar cycles currently used.
In a joint study by the University of Warwick and the British Antarctic Survey, scientists found that severe magnetic storms occurred in 42 out of the last 150 years.
Great super-storms occurred in six years out of the last 150.
While a storm may only last a few days, it can be hugely disruptive to modern technology.
Super-storms can cause power blackouts, take out satellites, disrupt aviation and cause temporary loss of GPS signals and radio communications.
Lead author Professor Sandra Chapman, from the University of Warwick’s Centre for Fusion, Space and Astrophysics, said: “These super-storms are rare events but estimating their chance of occurrence is an important part of planning the level of mitigation needed to protect critical national infrastructure.
“This research proposes a new method to approach historical data, to provide a better picture of the chance of occurrence of super-storms and what super-storm activity we are likely to see in the future.”
The Carrington storm of 1859 is widely recognised as the largest super-storm on record, but predates even the data used in this study.
The analysis led by Prof Chapman estimates what amplitude it would need to have been in order to be in the same class as the other super-storms.
Professor Richard Horne, who leads Space Weather at the British Antarctic Survey, said: “Our research shows that a super-storm can happen more often than we thought.
“Don’t be misled by the stats, it can happen any time, we simply don’t know when and right now we can’t predict when.”
Activity from the sun drives space weather. While smaller scale storms are common, occasionally larger storms occur that can have a significant impact.
One way to monitor this space weather is by observing changes in the magnetic field at the Earth’s surface.
High quality observations at multiple stations have been available since the beginning of the space age in 1957.
The sun has around an 11-year cycle of activity which varies in intensity and this data covers only five cycles of solar activity.
Scientists say that if a better estimate of the chance of occurrence of the largest space storms over many solar cycles is wanted, they need to look back further in time.
In 2012 the Earth narrowly avoided trouble when a coronal mass ejection from the sun missed the Earth and went off in another direction.