The Carrington Event was the strongest geomagnetic storm ever recorded, peaking on September 1–2, 1859, during a period of high solar activity. It caused bright lights in the sky, called auroras, which were seen around the world. The storm also led to sparks and fires in telegraph stations. Scientists believe the storm was caused by a large burst of solar particles, called a coronal mass ejection (CME), from the Sun colliding with Earth's magnetosphere.
This storm was linked to a very bright solar flare observed on September 1, 1859. British astronomers Richard Carrington and Richard Hodgson recorded this flare independently, marking the first known observations of a solar flare. A storm of this strength today could cause major electrical problems, power outages, and damage to the electrical grid.
History
On September 1 and 2, 1859, one of the largest magnetic storms recorded by ground-based instruments occurred. Scientists estimate the strength of this storm, measured as Dst, to be between −0.80 and −1.75 μT.
This magnetic storm is believed to have been caused by a coronal mass ejection (CME), which is a large group of charged particles released from the sun. This particular CME traveled directly toward Earth and covered a distance of 150 × 10^ km (93 × 10^ mi) in 17.6 hours. Most CMEs take several days to reach Earth, but this one moved quickly. Scientists think a previous CME, possibly linked to a bright aurora seen on August 29, may have made a path through the solar wind plasma, allowing this faster CME to travel more quickly.
On September 1, 1859, just before noon, two English astronomers, Richard Carrington and Richard Hodgson, independently observed and recorded the first known solar flare. They shared their findings in a scientific journal called Monthly Notices of the Royal Astronomical Society and displayed their drawings of the event at a meeting of the Royal Astronomical Society in November 1859.
A Scottish physicist named Balfour Stewart noticed a change in Earth’s magnetic field, called a "magnetic crochet," in data from the Kew Observatory. This, along with a magnetic storm observed the next day, led Carrington to suspect a connection between the sun and Earth. However, he was unsure if the two events were related, writing, "one swallow does not make a summer" (meaning one event does not prove a pattern). Later, American mathematician Elias Loomis collected and published worldwide reports about the 1859 storm, supporting the observations made by Carrington and Stewart.
Impact
Auroras were seen around the world in both the northern and southern hemispheres. The aurora borealis over the Rocky Mountains in the United States was so bright that the glow woke up gold miners, who began to prepare breakfast because they thought it was morning. People in the northeastern United States could read a newspaper by the light of the aurora. The aurora was also visible from the poles to areas near the equator, such as south-central Mexico, Cuba, Hawaii, Queensland, southern Japan, China, New Zealand, and Colombia.
On Saturday, September 3, 1859, the Baltimore American and Commercial Advertiser reported that
Those who were out late on Thursday night saw another impressive display of auroral lights. The event was similar to one seen earlier, though at times the light was even brighter, and the colors were more varied and beautiful. The light seemed to cover the entire sky, like a glowing cloud, through which the stars faintly shone. The light was brighter than the full moon but had a soft and delicate quality. Between 12 and 1 a.m., when the display was at its peak, the quiet streets of the city looked both beautiful and unusual under this strange light.
In 1909, an Australian gold miner named C. F. Herbert described his observations in a letter to the Daily News in Perth:
I was mining for gold at Rokewood, about four miles from the town of Rokewood in Victoria. Myself and two friends saw a bright reflection in the southern sky around 7 p.m. Within about 30 minutes, a scene of incredible beauty appeared: Lights of every color came from the southern sky, one color fading and another taking its place, sometimes more beautiful than the last. The lights rose toward the top of the sky, turning purple at the highest point, and curled around, leaving a clear strip of sky that looked like four fingers held at arm’s length. The northern side of the sky was also lit with beautiful colors, curling around the top of the sky. These colors were thought to be a copy of the southern display, as the colors in both areas always matched. This was a sight that could never be forgotten and was considered the greatest aurora ever recorded. Some saw it as a sign of nature’s beauty and the laws of the universe, while others feared it was a warning of disaster.
Because of electric currents caused by the aurora’s electromagnetic field, telegraph systems across Europe and North America failed. In some cases, operators received electric shocks. Telegraph poles sparked. Some operators continued sending and receiving messages even after disconnecting their power supplies. The following conversation took place between two telegraph operators in the United States on the night of September 2, 1859, as reported in the Boston Evening Traveler:
Boston operator (to Portland operator): "Please disconnect your power source completely for fifteen minutes."
Portland operator: "Will do so. It is now disconnected."
Boston: "Mine is disconnected, and we are using the aurora’s current. How do you receive my writing?"
Portland: "Better than with our batteries on. The current comes and goes gradually."
Boston: "My current is very strong at times, and we can work better without batteries, as the aurora seems to cancel out and strengthen our batteries alternately, making the current too strong for our relay magnets. Let’s work without batteries while this happens."
Portland: "Very well. Shall I go ahead with business?"
Boston: "Yes. Go ahead."
The conversation lasted about two hours without using battery power, relying only on the current from the aurora. This was the first time in history that more than a few words were transmitted in such a way.
Similar events
Another strong solar storm happened in February 1872. Less severe storms occurred in 1921 (this was similar to others in some ways), 1938, 1941, 1958, 1959, and 1960, when radio signals were widely disrupted. The flares and CMEs of the August 1972 solar storms were similar in size and strength to the Carrington event; however, unlike the 1859 storms, they did not cause an extreme geomagnetic storm. The March 1989 geomagnetic storm caused power outages in large parts of Quebec, while the 2003 Halloween solar storms were the most powerful solar explosions ever recorded. On July 23, 2012, a "Carrington-class" solar superstorm (including a solar flare, CME, and solar electromagnetic pulse) was observed, but it passed by Earth about nine days away from hitting it. During the May 2024 solar storms, an aurora borealis was seen as far south as Puerto Rico.
In June 2013, researchers from Lloyd's of London and Atmospheric and Environmental Research (AER) in the US used data from the Carrington Event to estimate that a similar event today could cost the US between $600 billion and $2.6 trillion (about $794 billion to $3.44 trillion in 2024). This would be about 3.6 to 15.5 percent of the US's yearly economic output. Research also shows that large geomagnetic storms could affect agriculture. This happens indirectly, as access to things like fertilizer and pesticides might be lost if industrial production is disrupted. Studies suggest this could reduce global crop yields by 38 to 48 percent, with up to 75 percent loss in areas like Central Europe.
Other studies have looked for signs of big solar flares and CMEs in tree rings (carbon-14) and ice cores (beryllium-10). Evidence of large solar storms was found around 774–775 and 993–994. Carbon-14 levels from 775 suggest an event 20 times stronger than usual and 10 times bigger than the Carrington Event. An event around 7176 BCE might have been even larger than the 774–775 event, based on this data.
It is still unclear if solar flares on the Sun work the same way as superflares on other stars. The Sun might be different in size and how fast it spins compared to stars that produce superflares.
Other evidence
Scientists have studied thin layers of nitrate-rich ice cores to learn about past solar storms that happened before reliable observations existed. This idea is based on the belief that high-energy particles from the sun would change nitrogen in the air, creating compounds like nitric oxide. These compounds would not mix too much with the atmosphere before being trapped in snow and ice.
In 1986, some scientists said ice cores from Greenland showed signs of individual solar events, including the Carrington Event. However, more recent research suggests that sudden increases in nitrate levels in ice cores are more likely caused by events on Earth, such as forest fires. These nitrate spikes match other chemical signs found in smoke from known forest fires. Also, nitrate levels in ice cores from Greenland and Antarctica do not match, which weakens the idea that they were caused by solar proton events.
A 2024 study examined computerized magnetic field measurements from observatories in Kew and Greenwich. The study found that the speed of magnetic field changes was much higher than expected for that area. The changes were faster than the highest recorded levels from modern digital measurements, which were about 350–400 nT/min.