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Just before noon on September 1, 1859, an English amateur astronomer named Richard Carrington was at his private observatory in Redhill, Surrey, projecting an image of the sun onto a screen and tracing sunspots when two patches of light flared up inside the largest spot group. They moved across the surface in five minutes and faded. Carrington had just become the first human being to record a solar flare. Another English observer, Richard Hodgson, watched the same event independently. They published side-by-side reports in the Monthly Notices of the Royal Astronomical Society and exhibited their drawings together at the November 1859 meeting.
Around the same minute Carrington was sketching, the Scottish physicist Balfour Stewart was at the Kew Observatory in west London. The needles on the magnetograph there suddenly twitched — a sharp, clean disturbance later named a magnetic crochet. Carrington noticed both events and suspected they were linked, but wrote, with characteristic English caution, that "one swallow does not make a summer."
The flare was the warning shot. The main attack arrived 17.6 hours later. A coronal mass ejection — a billion-ton bubble of magnetized plasma — crossed the 93 million miles between sun and Earth in a fraction of the usual transit time. Modern reconstructions suggest a previous CME on August 29 had cleared the slower solar wind out of the way, giving this one an open lane. It slammed into Earth's magnetic field on the night of September 1 and through September 2.
The auroras came first, and they came everywhere. The American mathematician Elias Loomis spent two years collecting eyewitness accounts from across the globe and published nine articles on the storm in the American Journal of Science. Aurora was reported from south-central Mexico, from Cuba, from Hawaii, from Queensland, from southern Japan and southern China, from New Zealand, and even from Colombia, just a few degrees off the equator. In the Rocky Mountains, gold miners woke up and started cooking breakfast because they thought it was morning. The Baltimore American and Commercial Advertiser wrote on September 3 that the light was "greater than that of the moon at its full" and that people had read newspapers by it. An Australian gold-digger named C. F. Herbert, writing fifty years later from Perth, remembered streams of color rising to the zenith and curling into rich purple, and recalled that "the superstitious and the fanatical had dire forebodings, and thought it a foreshadowing of Armageddon."
The other thing the storm did was electrify the telegraph network — the only large piece of electrical infrastructure that existed in 1859. Across Europe and North America, telegraph systems failed. Wooden telegraph pylons threw sparks. Operators received electric shocks. Paper tape caught fire in some offices. The most famous incident is preserved in the Boston Evening Traveler. Late on September 2, the operator in Boston wired the operator in Portland, Maine, and asked him to disconnect his battery. The Portland operator did. The Boston operator disconnected his too. Then they kept sending messages to each other for about two hours, powered entirely by current the aurora was inducing in the wire. "The current comes and goes gradually," Portland reported. It was the first time on record that more than a word or two had been transmitted on aurora alone.
When researchers compute how strong this storm actually was, they push against the limits of the instruments that recorded it. Estimates of the disturbance index, Dst, range from −0.80 to −1.75 microtesla, comfortably the largest in the magnetometer era. A 2024 study by the British Geological Survey digitised the original 1859 paper traces from the Kew and Greenwich observatories and found the magnetic field at London was changing at over 700 nanotesla per minute — almost twice the 1-in-a-hundred-years extreme rate inferred from modern digital records. Earlier comparisons placed the 1872 storm and the August 1972 storm in roughly the same size class as Carrington, but only Carrington produced a true global geomagnetic catastrophe.
The sun has not stayed quiet since. The May 1921 storm caused widespread radio disruption and damaged telegraph equipment in New York City. The March 1989 storm collapsed the entire Hydro-Québec grid in 90 seconds and left six million people without power. The 2003 Halloween storms produced the most powerful solar flares ever recorded with modern instruments. And on July 23, 2012, a Carrington-class CME erupted from the far side of the sun and crossed Earth's orbit — but Earth had been at that point in space nine days earlier. NASA's Sten Odenwald put it bluntly: a hit would have caused world-changing damage to satellites and power grids.
Older proxy records make the modern era look mild. Carbon-14 spikes in tree rings show enormous solar particle storms in 774–775 CE and 993–994 CE — the so-called Miyake events. Beryllium-10 in ice cores points to a storm around 7176 BCE that may have eclipsed even the 774 event. The 774 storm has been estimated at perhaps ten times the size of Carrington and twenty times the sun's normal activity range.
A 2013 study by Lloyd's of London and Atmospheric and Environmental Research put a number on what a Carrington repeat would do to the United States alone. Their estimate ran from $600 billion to $2.6 trillion in damages — between 3.6 and 15.5 percent of annual GDP, before accounting for downstream losses. A 2024 paper added agricultural collapse to the picture: with industrial inputs like fertiliser and pesticides interrupted, modelled crop yields fell 38 to 48 percent globally and up to 75 percent in central Europe. In 1859, the world's most advanced electrified machine was a wire on a pole, and even that wire shocked the men who held it.