Solar storms hit the Earth every 25 years

Solar storms are caused by disturbances in the Sun that send charged particles into space. It's when those particles hit the Earth’s magnetosphere that the storm hits. The particles can come from coronal mass ejections (CME), co-rotating interaction regions (CIR) and coronal holes that emit a high-speed solar wind current (twice as fast).

Solar storms powerful enough to cause failures in electronic equipment, including aviation and communication equipment, power grids and satellites, is not a rare phenomena: they hit the Earth every 25 years, according to a new study carried out by a team of scientists from the University of Warwick and the British Antarctic Survey and published in the magazine Geophysical Research Letters. Additionally, there are less strong, albeit dangerous, solar events every three years or so.

In summary, scientists have identified two types of powerful magnetic storms:

Great super storms, the most powerful that occur every 25 years on average severe, weaker storms occurring every three years

The analysis, which used historical data from the last 14 solar cycles, to expand scientists' previous estimates of the probability of space-based super storms, showed that “severe” space super storms have occurred 42 times in the last 150 years, and the largest super storms occurred six times within 150 years.

Solar cycles

Scientists have been able to detect super storms dating back 150 years by examining magnetic field records at opposite ends of the Earth (UK and Australia). This result was made possible by a new way of analysing historical data from the last 14 solar cycles, long before the space age began in 1957, rather than using the last five solar cycles commonly used in this type of analysis.

These solar or geomagnetic storms can originate with solar flares, which explode in the Sun during years of high solar activity and can cause blackouts, shutting down satellites, disrupting aviation and causing a temporary loss of GPS signals and radio communications.

"These super storms are rare events, but estimating the likelihood of them occurring is an important part of planning the level of mitigation needed to protect countries' critical infrastructures. This research proposes a new method to approach historical data, to provide a better picture of the possibility of occurrence of super storms and what activity we are likely to see in the future,” explains Sandra Chapman, study leader.

The Carrington event of 1859

The largest super solar storm in recorded history is known as the Carrington event and took place in 1859. This storm shut down some telegraph systems in different parts of the world, started some fires and even affected some telegraph operators. It is estimated that if a storm as powerful as the Carrington event were to occur today, it would cause thousands or even billions of euros in damage. The Carrington event was not part of the study, because the data that the researchers analyzed did not go that far back, but such a storm could be considered as a super solar storm.

Given that technology makes us more dependent on our current lives, understanding and predicting space weather is a priority. Ships like SDO (Solar Dynamics Observatory) or the Parker Solar Probe aim to increase our understanding of the Sun and the ability to predict these dangerous geomagnetic storms.

Reference: S.C. Chapman, R.B. Horne, N.W. Watkins. Using the aa index over the last 14 solar cycles to characterize extreme geomagnetic activity. Geophysical Research Letters, 2020; DOI: 10.1029/2019GL086524