The source was actually 90 million miles away. A wave of particles from our fiery sun bombarded Earth’s upper atmosphere, generating a geomagnetic storm that painted skies and disrupted electrical systems.
Now, displays newly discovered data that this event in February 1872 ranks among the three largest geomagnetic storms to hit the Earth to date. The findings reveal that these large events – supergeomagnetic storms – are more common than scientists previously realised, posing a major risk if hit in today’s technology-heavy society.
“The intensity of the geomagnetic solar storm was excessive and possibly one of the largest,” said Hisashi Hayakawa, the study’s lead author. “Such a strong geomagnetic storm would completely destroy modern civilization.”
Storms that are off the charts
The most intense supergeomagnetic storm is said to be the Carrington Event of September 1859, named after the British astronomer who helped shed light on it. The storm brought aurora borealis, or aurora borealis, as far as Tahiti – a big surprise since most auroras cluster around the Earth’s poles. Power surges paralyzed the world’s telegraph systems and halted messages.
The Carrington event was thought to be a unique event, but scientists are learning that is not true.
Another supergeomagnetic storm occurred in May 1921, the largest geomagnetic storm of the 20th century. The storm, sometimes called the New York Railroad storm, brought with it spectacular nighttime northern lights. It also disrupted and damaged telephone and telegraph systems connected to rail systems in New York City and around the state.
Now, the new study adds a third storm — from February 1872 — to the geomagnetic hall of fame, ranking as intense, if not more intense, than the others by some measures. The storm brought the aurora even further south than the Carrington Event, causing magnetic disturbances on Earth equal to or worse.
“Some of the colors mentioned in this event in terms of aurora coloring and then the behavior, in my opinion, is even more explicit than what was documented in [Carrington] event, says Delores Knipp, co-author and space physicist at the University of Colorado at Boulder. “It is likely that the level of magnetic disturbance or disruption is as large as the Carrington Event.”
Searching for geomagnetic clues from the past
Analyzing an event that you did not personally witness requires a little detective work.
Formal scientific observations of the event were limited in 1872, but researchers found upwards of 700 reports of the event from overlooked sunspot records, magnetic field records, newspaper clippings, telegraph operators, ship records, and whatever else was available.
Using the documents, Hayakawa and his colleagues at the US National Solar Observatory and the Royal Observatory of Belgium assessed the intensity, duration and origin of the storm. They also reconstructed conditions to see how far the aurora likely extended during the storm. The study took about six years to complete.
Northern lights were seen in very unusual places near the equator. A telegraph operator in Mumbai reported strong ground currents at 19.30 on 4 February 1872 until 07:00 on February 5, with the Northern Lights clearly visible from 20:30 to 04:30. A news article stated that “aurora was brilliant in the extreme” in Aden. A bright arc was reported in Shanghai.
“It was really surprising to scientists as well, because India is far away from the magnetic pole,” said Hayakawa, a space physicist at Nagoya University in Japan. “Generally speaking, to expand the auroral oval, the geographic area, we need a stronger geomagnetic storm.”
But the origins of the massive storm were quite modest. By analyzing sunspot records, the team found that the storm likely originated from a medium-sized sunspot group. Extreme geomagnetic storms usually come from huge sunspots.
“Even though they may not be that big, the real thing is the complexity” of the sunspot region, Knipp said. She said it’s troubling that such an intense storm was created from a moderate sunspot group, but agencies around the world help track and study these triggers on the sun — before they hit Earth.
Three supergeomagnetic storms in the past two centuries might not seem like a lot, but scientists say it’s too often for comfort.
Space physicist Dan Baker, who was not involved in the research, said he is surprised to see another incredibly intense storm occur relatively soon after the famous Carrington Event. He said the February 1872 event “adds to the sense that large, highly disruptive solar events and resulting geomagnetic storms are more common than most people assume.”
“If the sun is producing Carrington events or major disturbances basically every solar cycle or even every other solar cycle, then we better sit up and take notice,” said Baker, director of the University’s Laboratory for Atmospheric and Space Physics of Colorado at the University of Colorado. Erratic.
In fact, one such supergeomagnetic storm missed Earth in July 2012. Many media did not cover the potentially devastating event, but the storm was the most powerful in more than 150 years.
A storm of that size would cause many problems in modern society, Hayakawa said. It would knock out energy, communication and satellite systems, which we have become so used to in our daily lives.
Still, the occurrence of such an event remains rare, he said. Several parameters must match: the Sun must emit a rapid eruption, the Sun’s and Earth’s magnetic fields must be precisely coupled, and the storm must be very large. Then it must be directed towards the earth.
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