The Carrington Event

It was a sight never to be forgotten, and was considered at the time to be the greatest aurora recorded […]. The rationalist and pantheist saw nature in her most exquisite robes, recognising, the divine immanence, immutable law, cause, and effect. The superstitious and the fanatical had dire forebodings, and thought it a foreshadowing of Armageddon and final dissolution.

–C.F. Herbert

If skywatchers could pick any time and place to be alive, many might opt for North America during a quarter-century sliver of the 19th century. A cognizant citizen on that continent living between 1833 and 1859 might have been able to record a rather unlikely achievement: to experience a natural light at night strong enough to read a book or newspaper, as if by lamplight, twice.

One of America’s biggest legends, Abraham Lincoln, likely experienced both extraordinary occasions. Walt Whitman noted the profound influence of The Night the Stars Fell on Lincoln, who used it as a metaphor for the survival of the Union. In November 1833, a particularly strong iteration of the Leonids rained more like a meteor hurricane on the skies of North America than a meteor shower. Many believed the storm to be the signal of the end times, while others took the opportunity to read the newspaper by the brightness, caused by up to 100,000 meteors per hour.

Just a year after famously debating Stephen A. Douglas and a year before winning the presidency, Lincoln probably experienced the second event, too, though one did not need to reside in North America to catch the show this time.

In 1859, the entire world wondered if the end times were nigh.
A depiction of the Night the Stars Fell by Adolf Vollmy

On 28 August 1859, many people across the globe witnessed a stunning aurora. The northern lights crept so far south that Cubans witnessed the illumination directly overhead. Ships on the equator reported lights halfway to the acme of the night dome. Magnetometers – ground-based instruments that measure magnetic fields – registered off-the-chart readings. The nascent communication form of the mid-1850s, the electric telegraph, went haywire all night.

Today, scientists believe a coronal mass ejection caused the aurora of August 1859, but, at the time, no one knew the link between the sun’s emissions and dancing skies. This particular aurora was certainly a humdinger. Imagine the possibility of floating along the equator and watching the northern lights halfway up the sky on one side of your ship and the southern lights halfway up the other. As tremendous as this CME’s performance was, it was nothing compared to what was coming.

At 11:18 AM on 1 September, English astronomer Richard Carrington had his eye on the sun. Not literally, of course, or his eyes would no longer see. Instead, he had a telescope pointed at the star and projected the output onto a screen on the wall. Carrington was studying sunspots, which were mysterious curiosities at the time. He had noted a rather large grouping on that day in 1859, so he stenciled a copy of the projection onto paper. As he watched his personal solar motion picture, an intense white flash illuminated the wall. Carrington had never witnessed this phenomenon, so he looked at the clock and documented the time. The brightness persisted for five minutes.

No one knew then, but Richard Carrington had, by accident, become history’s first witness of a solar flare (for the record, a distinction he shares with another astronomer, Richard Hodgson, who also caught this specimen). Later, a magnetometer at Kew Gardens in England provided corroborating evidence for a spike at 11:18 AM.

As notable as this discovery was, it was still a preamble.

The September sunspots as sketched by Richard Carrington

Though a direct connection between solar flares and coronal mass ejections has not been definitively proved, they often occur at the same time. Because photons comprise solar flares, they move at the speed of light. The 1 September 1859 solar flare departed the sun just before 11:10 AM and reached Carrington’s projection at 11:18 AM. CMEs, on the other hand, have mass and, therefore, do not travel at the speed of light. One can infer, based on these velocities, that the solar flare of 1 September and the aurora from a few nights earlier were not sun-twins.

Heliophysicists, however, now believe a coronal mass ejection did follow Carrington’s flare. This second CME prompted the most intense geomagnetic storm in recorded history. Today, we call this tempest the Carrington Event.

Scientists postulate that the initial CME had “cleared out” the normal, ambient solar wind, a stream of charged particles that flows from the sun’s corona. CMEs can travel much more quickly than the solar wind, so one can imagine the first burst carrying all the particles in its way, leaving a plasma-free highway from the Sun to the Earth for CME number two.

Average coronal mass ejections can take multiple days to reach us. Seventeen hours after Carrington’s solar flare, the second CME impacted our planet. The speed might have been due to a combination of the plasma-free highway and the highly explosive nature of this CME.

A sketch of Carrington's house and observatory circa 1857

The night of September 1 and the morning of September 2 shocked the world. Literally.

The auroras were so intense that gold miners in the Rocky Mountains awakened at 1 AM, instinctively believing it was time to make breakfast. People in the Northeastern United States reported reading newspapers by the light from the sky, just as they had in 1833. Northern lights illuminated places as far south as Hawaii and south-central Mexico. Aurora australis beamed as far north as Queensland. On the equator, Colombians witnessed the storm.

Light shows were not the end of the story. The electrical system of the era – telegraphs – went berserk. Geomagnetic storms can produce fields that induce electrical currents on the surface of the planet. The deluge knocked much of the world’s telegraphs offline immediately, in many cases blessing operators with electrical shocks. Telegraph pylons began to spark. The malfunctioning equipment set telegraph offices on fire.

Then, something truly bizarre transpired.

The auroral currents induced such strong currents on the surface of the planet – according to Sten Odenwald and James Green, they were “continent-spanning currents” – that the telegraphs started working without batteries. The following conversation happened between telegraph operators in Boston, Massachusetts, and Portland, Maine:

Boston: “Please cut off your battery entirely for fifteen minutes.”

Portland: “Will do so. It is now disconnected.”

Boston: “Mine is disconnected, and we are working with the auroral current. How do you receive my writing?”

Portland: “Better than with our batteries on. – Current comes and goes gradually.”

Boston: “My current is very strong at times, and we can work better without the batteries, as the aurora seems to neutralize and augment our batteries alternately, making current too strong at times for our relay magnets. Suppose we work without batteries while we are affected by this trouble.”

Portland: “Very well. Shall I go ahead with business?”

Boston: “Yes. Go ahead.”

The discussion lasted on aurora-power for two hours.

An image of a CME in 2012 that missed Earth, one of the only known explosions comparable to the 1859 event; the small white circle represents the size of the Sun - NASA

Noticing the intense activity after the solar flare, Carrington believed the flash, the aurora, and the sunspots were all connected. Conclusive evidence for this bond did not arise until the end of the 19th century, long after the death of Carrington. However, his 1859 intuition kickstarted the inquiry into the Sun’s emissions, so scientists dubbed the storm with his name.

To date, the Carrington Event remains the largest recorded geomagnetic storm. Scientists measure the effects of the solar wind and CMEs on the disturbance storm time index, in terms of nanoTeslas, the unit of magnetic flux. Normal solar wind produces auroras on the scale of -50 nT. The worst modern geomagnetic storm knocked out the electrical grid of millions of Canadians in 1989, registering -600 nT. Though we lack accurate measurements from the era, some estimates put the Carrington Event at -1750 nT! The image above displays a CME that missed the Earth in 2012, likely one of the largest ever recorded. The small white circle represents the size of the Sun. Had this ejection intersected our planet, it would have registered at -1200 nT. The scope of the Carrington Event was incomprehensible.

In 1859, humanity was far less reliant on electricity and gadgetry. Today, society would not function without it. What would happen if the Carrington Event occurred today? Using the 1989 storm as a barometer, the results would be staggeringly bad. Nearly every satellite would fry, causing widespread informational problems. As bad as losing the satellites would be, many of them were designed to exist in space. They bask in the solar wind constantly and can absorb some sun storms. Here on the surface, another aspect of our lives was not at all designed to deal with sun emissions: the electrical grid. Many experts warn that the planet’s electrical grids operate extraordinarily close to the margins of failure without factoring in geomagnetic storms. A torrent the size of the Carrington Event could pulverize the worldwide grid for weeks or months. According to the National Academy of Sciences, a storm of that magnitude could inflict more than $2 trillion in infrastructure damage. They predict some of the largest transformers might require years to repair.

It is not hyperbole to suggest that a Carrington Event in the 21st century might temporarily send us back to 1859.

Fortunately, for the people of the time, the impacts of the storm were mostly ephemeral. Several nights of resplendent shows in the sky wowed the world. The event also sent us down a path of solar exploration that led to a better understanding of the emissions that now bear Richard Carrington’s name. For Abe Lincoln and others of the era, it was the second awesome treat from the cosmos in one lifetime.

May 2024 vs. Carrington sunspot - graphic by SpaceWeather

BONUS FACT: The impetus for this series of articles arose thanks to the solar storms of May 2024, which brought an aurora even to The Mountains Are Calling Headquarters in Ohio. Simultaneous anticipation and dread grew among skywatchers, as sunspots appeared that rivaled those from the Carrington Event, as displayed in the image above. An active region that big might bring colorful skies to areas of the planet unaccustomed to seeing them, but it could also bring electrical Armageddon. Thankfully, disruptions to the world’s gadgets did not manifest, while the auroras did. The storms peaked on 11 May with a disturbance storm time index reading of -412 nT.

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