× close
An aurora map of Japan showing observations at Okazaki on February 4, 1872. Reproduced with the kind permission of Shounji Temple (contrast emphasized).Credit: ©︎ Shounji Temple
In early November of this year, aurora borealis were observed at surprisingly low latitudes, from Italy to Texas. Such phenomena demonstrate the effects of the Sun’s coronal mass ejections on Earth’s magnetic field and atmosphere. Although it was much more dramatic than this recent light show, it was nothing compared to the massive solar storm of February 872.
The resulting aurora displays covered the Earth, and aurora borealis were observed in locations close to the equator, such as Bombay and Khartoum. An international team of scientists from nine countries has published a detailed study of this historically significant event, tracing the origin of the sun and its far-reaching impact on Earth.
This storm caused widespread disruption to telegraph communications, but in today’s technology-dependent society, such a storm would disrupt power grids and satellite communications. Their findings confirm that such extreme storms are more common than previously thought.
The modern world is increasingly dependent on technological infrastructure such as power grids, communication systems, and satellites. However, this dependence makes us increasingly vulnerable to the effects of large geomagnetic storms.
“The longer the electricity supply is likely to be cut off, the more society, especially people living in urban areas, will have to struggle to cope,” said Associate Professor Hayakawa, lead author of the study published in 2006. explains. astrophysical journal.
In the worst case scenario, such storms can be large enough to destroy power grids, communication systems, aircraft, and satellites. “Can we maintain our lives without such infrastructure?” Hayakawa says. “Well, let’s just say it’s very difficult.”
Extreme storms like this are rare. Two such storms stand out in recent research. The Carrington Storm of September 1859 and the New York Railroad Storm of May 1921. The new study suggests that another storm, the Chapman-Silverman storm of February 1872, should also be considered as one of them. Such extreme events.
At the time, the storm was large enough to affect technical infrastructure even in the tropics. Telegraph communications on the undersea cable connecting Bombay (Mumbai) and Aden in the Indian Ocean were disrupted for several hours. Similar disturbances were reported on landlines between Cairo and Khartoum.
× close
Geographic overview of aurora visibility on February 4, 1872. Credit: Hayakawa et al. (2023)
The multidisciplinary team of 22 scientists was led by Japan’s Nagoya University (Hisashi Hayakawa), the US National Solar Observatory (Edward Kliver), and the Royal Observatory of Belgium (Frederick Kret). Twenty-two researchers used historical records and modern technology to evaluate the Chapman-Silverman storm from its solar origins to its impact on Earth.
For the origin of the sun, the research group turned to historical archives, particularly records from Belgium and Italy, to largely forgotten records of sunspots. For the terrestrial impact, we used geomagnetic measurements recorded at various locations such as Bombay (Mumbai), Tiflis (Tbilisi), and Greenwich to assess the temporal evolution and strength of the storm. They also examined hundreds of reports of visual auroras caused by the storm in various languages.
One of the more interesting aspects of the 1872 storm is that it likely arose from a medium-sized but complex sunspot cluster near the center of the solar disk, as confirmed by analysis of the Belgian and Italian solar records. did. These findings suggest that even a moderate-sized sunspot group produced one of the most extreme geomagnetic storms in history.
Hayakawa and his colleagues expanded their search for historical auroras by combing through records in libraries, archives, and observatories around the world. They identified more than 700 auroral records showing that the night sky was lit up with spectacular auroral displays, from the polar regions to the tropics (up to about 20° latitude in both hemispheres).
× close
Belgian sunspot map showing the solar surface on February 3, 1872 (RAS MS Bernaerts, v. 3, f. 26; courtesy of the Royal Astronomical Society). Credit: ©︎ Royal Astronomical Society (RAS MS Bernaerts, v. 3, f. 26)
“Our findings confirm that the February 1872 Chapman-Silverman storm was one of the most extreme geomagnetic storms in recent history. Its magnitude was greater than that of September 1859. It was comparable to the Carrington storm in May 1921 and the New York railroad storm in May 1921,” Hayakawa said. “This means we now know that the world has experienced at least three geomagnetic superstorms in the past two centuries. A space weather event that can cause such significant impacts poses a risk that cannot be ignored. It means.”
Hayakawa said: “Such extreme events are rare. While we are lucky that we have not encountered such a superstorm in modern times, it is unfortunate that such a superstorm has occurred three times in 60 years. represents a threat to modern society.” Preservation and analysis of historical records is therefore important for assessing, understanding and mitigating the impact of such events. ”
Recent auroras have been observed in northern Greece and the northern United States. Currently, the Sun is nearing its solar cycle maximum, which is predicted to occur in 2025, and auroral activity is expected to increase in the coming years.
Researchers from nine countries collaborated on this study.