The Carrington Event
The 1859 Solar Storm That Set Telegraph Offices on Fire
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This audiobook explores how geomagnetic storms work, the science behind coronal mass ejections, and what evidence remains of similar events. It examines the specific impacts on telegraph networks, compares the 1859 storm to modern space weather, and discusses the potential dangers a similar event poses today. The book traces the history of aurora observations and explains how solar activity affects Earth's magnetic field.
Listeners will find this audiobook valuable whether they are students of earth sciences, professionals in power grid management, or anyone curious about how solar storms can disrupt modern technology.
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On September 1 and 2, 1859, a geomagnetic storm of extraordinary strength swept across Earth. It was one of the largest storms recorded by ground-based magnetometers, with estimates of its intensity—measured as Dst—ranging from negative 0.80 to negative 1.75 microteslas. The storm’s power was felt in telegraph offices around the world, where equipment sparked and caught fire. This event, known as the Carrington Event, marked a rare moment when solar activity disrupted human technology on a global scale.
The geomagnetic storm was likely triggered by a coronal mass ejection, or CME, moving directly toward Earth at an unusually fast pace. This particular CME took only 17.6 hours to travel the 150 million kilometers—93 million miles—between the Sun and our planet. Normally, such events take several days to arrive. But it’s believed this one was accelerated by a previous CME, possibly the one responsible for a major aurora on August 29, which may have cleared out solar wind plasma and paved the way for what became known as the Carrington Event.
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The Carrington Event of 1859 sent auroras dancing across the sky in ways people had never seen before. These northern lights were visible not just near the poles, but as far south as places like south-central Mexico, Cuba, Hawaii, Queensland, southern Japan, China, New Zealand, and even close to the equator in Colombia. In the United States, the aurora borealis over the Rocky Mountains was so bright it woke gold miners, who thought it was morning and began preparing breakfast. People in the northeastern states could read newspapers by the light of the aurora. The display was so vivid that it reached low latitudes where such phenomena are rarely seen.
On Thursday night, people who were out late were treated to another stunning aurora. The display resembled the one on Sunday, but at times it was even more brilliant, with richer and more varied colors. The lights spread across the sky like a glowing cloud, dimly letting through the brighter stars. The glow was stronger than a full moon, yet soft and gentle, wrapping everything in its presence. At around midnight, when the aurora reached its peak, the quiet city streets looked both beautiful and strange under that unusual light.
I was gold-digging at Rokewood, about four miles from Rokewood township in Victoria. Myself and two mates were looking out of the tent when we saw a great reflection in the southern heavens at about 7 o'clock p.m. In about half an hour, a scene of almost unspeakable beauty presented itself. Lights of every imaginable color were issuing from the southern heavens, one color fading away only to give place to another if possible more beautiful than the last. The streams mounted to the zenith, but always becoming a rich purple when reaching there, and always curling round, leaving a clear strip of sky, which may be described as four fingers held at arm's length. The northern side from the zenith was also illuminated with beautiful colors, always curling round at the zenith, but were considered to be merely a reproduction of the southern display, as all colors south and north always corresponded. 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.
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On the night of 2 September 1859, a powerful solar storm disrupted telegraph systems across Europe and North America. The geomagnetically induced currents caused failures in many lines, sending electric shocks to operators and making telegraph pylons spark. Some operators managed to keep communicating after disconnecting their power supplies. The Boston Evening Traveler reported a conversation between two operators on the American telegraph line between Boston, Massachusetts, and Portland, Maine, during that same night.
In Boston, a man reported that the current in the telegraph office was very strong at times, and they found it easier to operate without the batteries. The aurora seemed to alternately boost and neutralize the power, making the current too strong for the relay magnets. He suggested they work without batteries while the problem persisted.
For about two hours, operators managed to carry on a conversation without any battery power, relying entirely on the electrical current generated by the aurora. This marked the first known instance in which more than a brief exchange was transmitted in this way.
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Another strong solar storm struck in February 1872. There were less severe storms in 1921, 1938, 1941, 1958, 1959, and 1960, with radio disruption reported during the 1960 event. The August 1972 storms were similar in size and strength to the Carrington event, though they didn’t trigger an extreme geomagnetic storm. In March 1989, a geomagnetic storm knocked out power across Quebec. The 2003 Halloween storms were the most powerful solar explosions ever recorded. On 23 July 2012, a “Carrington-class” solar superstorm was observed, but it missed Earth by about nine days. During the May 2024 solar storms, an aurora was seen as far south as Puerto Rico.
In June 2013, researchers at Lloyd's of London and Atmospheric and Environmental Research in the US used data from the Carrington Event to estimate how much a similar event today might cost the US. They calculated that a modern-day version could cause between $600 billion and $2.6 trillion in damage—roughly 3.6 to 15.5 percent of annual GDP. Beyond economic loss, studies also suggest that a major geomagnetic storm could hurt agriculture. Disrupted industrial production might cut off access to things like fertilizer or pesticides, potentially reducing global crop yields by 38 to 48 percent, with some areas like Central Europe seeing losses as high as 75%.
Scientists have searched for evidence of massive solar storms in tree rings and ice cores, looking for traces of carbon-14 and beryllium-10. In the years 774–775 CE, they found a clear signature of a solar storm—its carbon-14 levels were about twenty times higher than normal, making it far more intense than the Carrington Event. A similar event around 993–994 CE also left traces. Even earlier, an event in 7176 BCE may have been larger still, based on proxy data from those same isotopes.
Whether the physics behind solar flares is the same as that of even larger superflares remains uncertain. The Sun might differ in key ways from the types of stars known to produce superflares, such as in size and rotation speed.
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Scientists have studied ice cores from Antarctica and Greenland to trace back events in Earth’s atmosphere long before we had records of solar activity. These cores contain thin layers rich in nitrates, which help researchers reconstruct past solar storms. The method relies on the idea that solar energetic particles can ionize nitrogen in the air, creating nitric oxide and other oxidized nitrogen compounds. These chemicals eventually fall to Earth with snow and get trapped in ice, preserving a record of such events across centuries. This technique has allowed scientists to identify major solar storms from before reliable observation began, including one from 1859 known as the Carrington Event.
In 1986, researchers suggested that data from Greenland ice cores pointed to solar particle events, including the Carrington Event. But more recent studies have cast doubt on that idea. The nitrate spikes found in the ice don’t seem to come from solar protons after all. Instead, they may result from Earth-based events like forest fires. These spikes correlate with chemical markers known to come from fire plumes. Ice core data from Greenland and Antarctica don’t match up either, weakening the theory that they reflect proton events. The hypothesis now faces serious challenges.
A 2024 study looked at old magnetogram readings from Kew and Greenwich observatories. It found that the changes in Earth’s magnetic field during the 1859 storm were far more extreme than anything recorded in the digital era. The data showed that rates of change exceeded 700 nT/min, which is much higher than the 350 to 400 nT/min considered a 1-in-100-years event based on modern records. This suggests the magnetic disturbance was far more intense than anything seen since digital monitoring began.
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Overview
Richard Christopher Carrington was an English astronomer who made important discoveries about the Sun in the 1850s and 1860s. In 1859, his observations showed that solar flares exist and can affect Earth's aurorae and electrical systems. A year later, in 1863, he recorded sunspot movements that revealed how the Sun rotates at different speeds at different latitudes. Carrington lived from May 26, 1826, to November 27, 1875.
Life
Richard Christopher Carrington was born in Chelsea, the second son of a brewery owner, and entered Cambridge in 1844, though his father's wishes, not his own, shaped his early path toward the church. His interest in science grew, especially astronomy, after attending Professor Challis's lectures. After graduating as thirty-sixth wrangler in 1848, he took a job at the University of Durham observatory, but soon found it too limited. He resigned in March 1852 and turned his attention to star mapping, aiming to extend Bessel and Argelander's work to include fainter stars. He set up an observatory at Redhill, Surrey, in 1853, where he produced a detailed catalogue of circumpolar stars, earning the Royal Astronomical Society's Gold Medal in 1859. Meanwhile, he also began systematic solar observations, tracking sunspots and measuring the Sun's rotation, using a unique method involving gold wires and projected images. His work was interrupted by his father's death in July 1858, which left him managing the family brewery.
The great solar storm of 1859
Richard Christopher Carrington, working with fellow astronomer Richard Hodgson, documented sunspots and directly observed the massive solar outburst on September 1, 1859. Their independent reports were published together in the Monthly Notices of the Royal Astronomical Society, and their drawings of the event were shown at the society’s meeting in November 1859. The resulting geomagnetic storm struck Earth in the days that followed, mainly impacting the American continents. At the time, telegraph systems were the most affected; lines across Europe and North America failed, sometimes shocking operators. Telegraph pylons sparked, yet some operators continued sending and receiving messages even after disconnecting power. This event, named after Carrington’s observations, is now known as the Carrington Event, with similar occurrences classified as “Carrington-class.”
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Overview
A coronal mass ejection, or CME, is a massive release of solar plasma that shoots from the Sun’s outer atmosphere into space. These events are often linked to solar flares, though scientists haven’t fully understood their connection yet. When a CME travels through space and hits Earth’s magnetosphere, it can spark geomagnetic storms and beautiful aurorae. The most powerful recorded event like this happened in 1859, known as the Carrington Event. It knocked out parts of the new telegraph system in the United States, sparking fires and shocking operators. CMEs occur more frequently during solar maxima, about three a day, and less often near solar minima, around one every five days.
Physical description
Coronal mass ejections, or CMEs, are events that send massive amounts of matter from the Sun’s outer atmosphere into space. These eruptions carry plasma—mainly electrons and protons—along with magnetic fields. Often, those fields form a helical shape known as a flux rope. The average mass released during such an event is about 1.6 trillion kilograms, though that number is likely a low estimate since measurements only capture a two-dimensional view. CMEs come from twisted or sheared magnetic structures high in the Sun’s corona, where they're held in place by stronger magnetic fields above them.
Origin
CMEs begin in the Sun's lower corona where magnetic forces control events. The Sun's magnetic field, created deep inside by the solar dynamo, rises to the surface and forms concentrated regions called active regions with dipole structure and opposite magnetic poles. Over time, this magnetic flux spreads out and mixes with older remnants to become part of the quiet Sun. CMEs form above polarity inversion lines—boundaries where the vertical magnetic field flips direction—and can appear in active regions or even quiet areas between them. For a CME to erupt, vast amounts of energy must build up, stored mainly as magnetic energy from twisting or shearing motions. Some pre-eruption structures called sigmoids take on S or reverse-S shape due to shear, and are more common in certain hemispheres. Magnetic flux ropes—twisted tubes of magnetic energy—are part of the final CME structure, though whether they exist before eruption is still debated. Some pre-eruption structures also host prominences or filaments made of cooler material embedded in magnetic cavities.
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Overview
An aurora is a natural light show in Earth's upper atmosphere caused when charged particles from the Sun hit atoms in the air, making oxygen and nitrogen glow in colors like green, red, and purple. When seen near the poles, they're called polar lights or aurora polaris. In the Arctic, they're known as the northern lights or aurora borealis, and in the Antarctic, the southern lights or aurora australis. Auroras appear as curtains, rays, spirals, or flickering bands across the sky. They happen when solar wind from coronal holes or coronal mass ejections disturbs Earth's magnetosphere, changing how charged particles move. These particles enter the upper atmosphere and create light through ionization. The shape and intensity depend on how fast the particles are accelerated. Auroras also occur on other planets, brown dwarfs, comets, and some moons.
Etymology
The term aurora borealis first appeared in 1649, when Pierre Gassendi described an auroral display visible across France in 1621. Gassendi had read Galileo Galilei’s writings, who used the term in his work about aurora from 1619. The word entered English in 1828. Aurora comes from the Roman goddess of dawn, and the words borealis and australis derive from Greco-Roman wind gods—Boreas and Auster. The name "auroras" is now common in U.S. usage, though scientists often use "aurorae," the Latin plural. In some cases, aurora functions as an uncountable noun, with multiple sightings referred to simply as "the aurora."
Characterisation
Auroras appear most often in a band around 67 degrees north and south, known as the auroral zone, with the active region called the auroral oval. This oval shifts due to the solar wind, moving about fifteen degrees from the geomagnetic pole at noon and twenty-three degrees at midnight. The peak of the oval is slightly offset toward the night side, so auroras are seen furthest from the equator when the magnetic pole lies between the observer and the Sun, a time called magnetic midnight. Early studies by Elias Loomis in 1860, and later Hermann Fritz and Sophus Tromholt, showed that auroras mainly occur within this zone. In the north, they're known as the aurora borealis or northern lights, while in the south, the aurora australis or southern lights, which mirrors the northern patterns. During strong geomagnetic storms, like the one in 1859, the oval expands and brings auroras to lower latitudes—sometimes even to the tropics.
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