The Carrington Event: History's biggest solar storm
The Carrington Event of 1859 packed a bigger punch than any other recorded geomagnetic storm. How did it cause chaos, and could history repeat itself?
Image: stock.adobe.com
When Richard Carrington peered through his telescope on 1st September 1859, it was supposed to be just another normal morning. This British astronomer had plans to observe the Sun and sketch sunspots. As he studied the celestial body’s surface, he found the sunspots he was looking for, but also something unfamiliar to his trained eyes.
He was witnessing a peculiar kind of phenomenon completely unknown to scientists of his day: a solar flare. It wasn’t just any solar flare, either. It would kickstart what remains, to this day, the most intense geomagnetic storm on record. Aurora lights, usually only visible near the poles, could now be seen much further afield. Meanwhile, telegraph systems malfunctioned as they absorbed excessive electrical current.
This history-making geomagnetic storm came to be known as ‘the Carrington Event’, named after the astronomer who witnessed the flare that caused it. What impact did it have on the UK, and how does it compare to other, similar storms from history? We at Sky HISTORY also dare to ask: How much worse could the effects be were a repeat of the Carrington Event to happen today?
It was just another quiet morning…
It’s easy to imagine Richard Carrington’s nonchalance as he opened the shutter of his private observatory on 1st September 1859. From his vantage point near London, the blue morning sky would give him a clear view of the Sun. So, what were those ‘two patches of intensely bright and white light’ he saw emanating from it? He couldn’t be certain at the time, but the following night would give him a clue. Quite a few, rather chaotic clues, in fact…
Here in the UK, we’re accustomed to seeing the Northern Lights, but usually have to travel to Scotland or northern England to see them. However, in the (very) early hours of 2nd September 1859, auroras could be seen dancing in the sky much further south as well. Even in the dead of night, the light was bright enough to wake up some people who mistook it for the morning sun.
Around the same time, telegraph operators noticed their equipment faltering. As telegraph wires became overloaded with electrical charge, sparks literally flew in telegraph stations, on some occasions starting fires. What was happening? The pieces of the puzzle would soon start to come together. Unbeknownst to Carrington, one of his countrymen, fellow astronomer Richard Hodgson, had spied the same suspicious solar flare through his own telescope the previous morning…
What caused the Carrington Event?
The Carrington Event was started by a now scientifically known phenomenon – a ‘coronal mass ejection’ (CME). This is when the Sun spews plasma into the atmosphere, as it does regularly throughout the solar cycle. However, at certain points in this roughly 11-year cycle, CMEs can become especially frequent. Sometimes, the plasma can even collide with Earth’s magnetic field, setting off a geomagnetic storm.
When plasma ejected from the Sun in this way is on a collision course with Earth, it usually takes several days to get there. In the case of the plasma that caused the Carrington Event, it took just under 18 hours. This is thought to have been due to an earlier CME that essentially ‘cleared the way’ for the one on 1st September 1859. Solar flares are sometimes seen as harbingers of geomagnetic storms, but the precise relationship between these flares and CMEs is not well understood.
Do we need to worry about geomagnetic storms today?
How strong was the Carrington Event? Estimates vary widely, but fall in the range of -800 to -1,750 nanoteslas. A geomagnetic storm of this power is thought to occur only about once every 500 years. Nonetheless, we could have had a repeat of the Carrington Event much sooner than this – in 2012! Yes, the year once prophesied to bring about the end of the world. It’s also when a blast of plasma similar to that responsible for the Carrington Event only just missed Earth. What a close shave…
What would have happened if this plasma did hit Earth? We got a preview of sorts in 1989, when one geomagnetic storm took out the power grid in the Canadian province of Quebec. The Halloween solar storms of 2003 similarly damaged electrical systems. These days, satellites are trusted with detecting incoming solar storms. This gives authorities time to take precautions, like grounding flights and shielding the grid, to rein in the inevitable disruption to the public.
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