What was the Carrington Event, and why does it matter?

The sun – our blazing star – has a metaphorical dark side. It has the potential to cause our modern technological civilization to falter. We had a taste of our sun’s destructive effects on September 2, 1859. On that day, around the world, compasses at sea failed to work, causing some ships to become lost. Telegraph networks experienced disruption, with some telegraph lines catching fire. Tellingly, people as far south as the Caribbean and Mexico saw auroras. Scientists now believe that what happened on that day – 164 years ago – was an extreme geomagnetic storm. Since then, the 1859 storm has become known as the Carrington Event.

Many scientists and others wonder … what would happen if a Carrington Event took place today?

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The Carrington Event

Richard Carrington was a well-known British astronomer of the 19th century. His focus was the sun. He determined the position of the sun’s axis of rotation (the location of its north and south poles) and was the first to learn that the sun doesn’t rotate as a solid body, but that solar material goes around faster at the sun’s equator than at its poles. He discovered that the dark spots on the sun’s surface, called sunspots, vary in latitude over the 11-year solar cycle. He and Richard Hodgson saw the first bonafide solar flare.

On the first day of September 1859, he was observing sunspots when he saw a bright flash of light. Scholars now believe he saw the mighty coronal mass ejection (CME) – a powerful eruption near the sun’s surface, driven by kinks in the solar magnetic field – whose resulting shocks rippled through our solar system. One day later, on Earth, a great storm occurred in our world’s magnetic field. The effects of that great geomagnetic storm are now called the Carrington Event.

Coronal mass ejections (CMEs)

CMEs are common on the sun, especially when the sun is near the peak of its 11-year solar cycle. And aurora-watchers welcome them, because they cause the beautiful displays of auroras, aka northern or southern lights, seen at high latitudes. Nowadays, our spacecraft routinely record CMEs. But, in the 19th century, CMEs hadn’t been discovered yet (although there’d been hints that they existed).

Not until 1971 did the Helios spacecraft discover CMEs from ultraviolet observations.

Carrington Event report

Carrington immediately reported the flash to the Royal Astronomical Society. He probably didn’t give it much more thought until the next day … when the fast-moving solar particles had had time to travel across space to Earth, causing the geomagnetic field to go haywire. Wrapping Earth in a seething, writhing mass of high-energy particles, the blast of solar particles buffeted, squeezed and distorted Earth’s magnetosphere, releasing an estimated 10³⁵ electron volts of energy. That’s a ten followed by 35 zeroes. This amount of energy is equal to a 10-megaton nuclear bomb. It’s also equal to the amount of energy the sun releases in about 10 seconds.

It was the most powerful solar event ever yet recorded.

The effects of the Carrington Event

The effects of the September 2, 1859, solar storm were unprecedented. People saw auroras as far south as the Caribbean and Mexico. At some more northerly latitudes, it’s said the sky was so bright with auroras that birds, thinking it was morning, began to sing. But it wasn’t all awe and beauty. There were widespread stories of people receiving shocks from doorknobs and other metal objects, thanks to the induction of electrical currents. Around the world, compasses at sea failed to work, causing some ships to become lost. Telegraph networks experienced disruption, with some telegraph lines catching fire.

One apocryphal tale tells of a telegraph operator who received a shock from his machine, knocking him unconscious and awaking later to find his arm paralyzed. This story, while remaining uncorroborated, is certainly not beyond the realm of possibility.

The extreme geomagnetic storm subsided the following day. Work began to repair telegraph networks. The brilliant auroras faded from view, and the world returned to normal.

But the stories of the event remain to this day.

A bit of background

The Carrington Event was an extreme geomagnetic storm. To understand the 1859 event, we must understand the solar cycle. German amateur astronomer Samuel Heinrich Schwabe had just discovered the 11-year cycle in the year 1843. Schwabe had been observing the sun for over 17 years when he noticed that the number of sunspots on the sun’s surface varied over time. He also noticed that the period of this variation was about 11 years.

Schwabe’s discovery was a breakthrough in our understanding of the sun. It showed that our star is not a static object, but rather dynamic and ever-changing.

And – thanks to Schwabe’s tracking of the solar cycles – we know that the peak of Solar Cycle 10 was in February 1860. The Carrington Event happened just months earlier, in September 1859.

The sun’s magnetic field

The sun’s magnetic field creates the 11-year solar cycle, which peaks when the north and south magnetic poles of the sun swap places. Around the peak of each cycle, for a few years on either side, the sun can experience violent events, including increased coronal mass ejections (CMEs). We’re in such a time now, by the way. The peak of the current solar cycle is expected in the mid-2020s. You can read the sun news each day at EarthSky’s daily sun post.

When a CME leaves the sun, the sun expels around a billion tons of matter. And sometimes this solar material is directed toward Earth. When it arrives, the Earth experiences a geomagnetic storm, usually not an extreme one, but an awesome event nonetheless. At such times, the solar wind slams into our planet’s magnetic field, infusing Earth’s magnetosphere with high-energy particles.

From our viewpoint on the surface of Earth, one immediate effect is beautiful, bright auroras as the particles collide with atoms in the upper atmosphere, imparting their energy and causing the atoms to glow. This is a geomagnetic storm, and it can last for many hours.

News reports from the time

The Carrington Event was a hot story in newspapers of the day. The September 2, 1859, edition of The New York Times reported:

Last night the city was visited by one of the most brilliant displays of the aurora borealis that has been witnessed for many years. The sky was clear, and the stars shone with unusual brilliancy. About nine o’clock a faint light appeared in the north, which gradually increased in brightness until it reached the zenith. The aurora then assumed a variety of forms, and the sky was constantly changing. At times the whole heavens were illuminated with a brilliant light, and the stars were entirely obscured. The aurora continued for several hours and disappeared about midnight.

On September 3, 1859, The Boston Globe reported:

Yesterday there was a great magnetic storm which affected all the telegraph lines in the country. The telegraph lines in Boston were all interrupted for several hours, and some of them were so badly injured that they will not be repaired for several days. The storm also affected the magnetic compasses on ships, and some vessels lost their way.

And on September 5, 1859, The London Times reported:

On the night of the 1st and 2nd of September … the magnetic compasses were so much affected that it was impossible to steer by them. The aurora borealis was seen in many places where it is rarely seen, and in some places it was so bright that it was possible to read by it.

If a Carrington Event happened today

Today we live in a completely different world. Our technology is advanced, complex and ubiquitous. Where once telegraph lines sang their messages across the flat midwestern plains of the United States, now it’s the internet that connects us and everything we do.

The first undersea transatlantic telegraph cable came just a year before the Carrington Event, in 1858. It connected North America with Europe for the first time, allowing news to propagate around the world faster than ever before. Today, most of the world’s internet traffic flows through undersea cables of vast capacity. Existing cables flow with ever-multiplying streams of ones and zeroes, the telegraph songs of the digital age.

Computers manage our society. They affect every single aspect of our lives, from traffic control to power grids to banking to healthcare to entertainment. The birth of the integrated circuit gave us the modern world, appearing in all modern devices from toasters to televisions and cellphones to cars. What might another Carrington-type event do, if it were to induce large electrical currents in Earth’s magnetic field? What might happen to national power grids? 

There would almost certainly be widespread burnout of electronic circuits and the failure of power grids on a much bigger scale than the 1989 Quebec blackout from a solar storm. Many, many millions of people would likely be without power and unable to use phones or other devices.

The effects on satellites

In space, satellites would also fail as their electronics fried. This has happened several times during geomagnetic storms on a scale far smaller than the Carrington Event. The most recent was in March 2022, when 40 SpaceX Starlink satellites failed after a CME. They launched the day before the storm hit. But it wasn’t their electronic systems that failed. One effect of a geomagnetic storm is to increase atmospheric drag on the satellites. It pulled the satellites back toward Earth, where they burned up in the atmosphere.

Only about 1% of the world’s internet traffic transmits via satellite. However, in the banking industry, ATM and credit card transactions, the transfer of funds and banking messages all travel through satellites. Widespread communication loss would be inevitable. There would be utter chaos for a while. Recovery might take years.

Predicting the next one

If all this sounds frightening to you, let’s ask an important question to put it all in perspective. Just how likely is another Carrington Event? After all, it’s been 164 years since the last one. So do we view it as a blip, or do such events recur on longer timescales, or perhaps even at regular intervals? Can we predict the next storm and what its effects might be? And – perhaps the most important question – just how much notice might we get of an extreme, Carrington-like event?

Let’s start with the source of the problem: coronal mass ejections or CMEs. Yes, we know much more than we did about them since their discovery in 1971. But CMEs are unpredictable. Apart from the fact that they occur more frequently around solar maximum, due to that reorientation of the sun’s magnetic field, we don’t yet know enough about the mechanisms that generate CMEs to say when they will occur.

So, we have no way of knowing when a event similar to the Carrington Event might occur again. We also don’t know how often these events occurred before 1859. Before there were electric grids or devices, such storms probably went unrecorded apart from mentions of brilliant auroras.

Preparing for the next one

How much notice might we receive of an impending, society-changing, potentially catastrophic storm? Well, you’ll be pleased to know that scientists are fully aware of the dangers. They’re working hard using artificial intelligence to model when and where they could hit worst. NASA heliophysicists have created a system called DAGGER, but it could only give us an estimated 30 minutes’ warning of an approaching storm.

We now have the sun under constant observation from Earth and satellites. But when the sun releases a CME, it’s difficult to work out exactly how much material will hit us. Put simply, we don’t know which ones are the dangerous ones.

Hope rests on attaining a greater, more holistic and in-depth understanding of the sun’s magnetic field. One day, we might be able to predict the destructive geomagnetic storms of the future. We can harden our technology and power grids against damage in the same way that spacecraft have their electronics hardened against electrical currents. But that requires lots of money and the world’s politicians to recognize the dangers and act.

So far, they have not allocated nearly enough money and resources to protect us from civilization-destroying asteroids or, of course, the effects of climate change. There’s little reason to be optimistic that those in power will take the threat of another Carrington Event seriously.

Learning lessons from the Carrington Event

The Carrington Event, in the end, caused minimal damage in an age when there was little which could be damaged. But were it to occur today, it would be catastrophic. We really need to learn the lessons from our ancestors and treat the sun seriously as a threat as well a life-giver. If we do not, we will only have ourselves to blame when the next extreme geomagnetic storm hits.

Bottom line: The Carrington Event of 1859 was a massive geomagnetic storm triggered by activity on the sun. People saw auroras at low latitudes that were bright enough to read by.

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