The time scale of aurora activity on Earth is variable. The magnetic poles move, and auroras may appear at different latitudes across the globe. They are also affected by solar activity, which can cause powerful solar storms to push the auroras even further into the mid-latitudes.
A team of researchers have tracked auroral activity over the past 3,000 years to gain a better understanding of how auroras move, how they will move in the future and when solar storms could pose a threat.
Two researchers from Japan's National Institute of Polar Research have combined ancient literature with modern data to map the changing auroral zone over three millennia. They have created a video that covers 3,000 years worth of auroral drift by using historical accounts from different cultures.
Their research was published in the Journal of Space Weather & Space Climate. Ryuho Kataoka (associate professor at the National Institute of Polar Research) is the first author.
Kataoka, the first author, stated in a press release that "the accurate knowledge of the aural zone over the past 3000 years via the worldwide old witness record for auroras including those from low-latitude Japan" and that it helped them understand the extreme magnetic storms.
This study was largely based on science, not ancient writings. The study of magnetic evidence in rocks is called paleomagnetism. Researchers used paleomagnetic models for a time-based map of Earth's auroral zones.
The oval-shaped auroral zone changes over time. The auroras are found in a region between 20 and 30 degrees from the poles. However, this zone can extend further into the middle latitudes if powerful solar storms occur; even in regions like Japan.
Kataoka stated that the auroral zone is subject to change over time and that the deformation and sporadic expansions of the auroral oval have been documented in historical documents from over a thousand year ago.
(L: Herman Fritz/Das Polarlicht; R: Kataoka and Nakano, JSWSC, 2021)
Above: A map showing the auroral isochasm between 1700 and 1872. Below is a sketch showing the reconstruction of the auroral zone between 1800 CE and 1870 CE. It also shows the possible deformation caused by a 170-year integration.
The King's Mirror, an Old Norse text, was one of the documents that the researchers used. It has 70 chapters and is meant to be a dialogue between fathers and sons. Magnus Haakonsson is the son and Haakon IV Haakonsson is the father.
This text was written to teach Magnus royal affairs and prepare him to reign. It focuses on matters of court, morality and trade. The King's Mirror contains descriptions of auroral activities over Greenland between 1200 and 1300 CE.
They also reviewed a Japanese text called Nippon Kisho-Shiryo that contains information about auroras and other phenomena. The Nippon Kisho-Shiryo shows a cluster of auroras at 1200 CE. This is consistent with what The King's Mirror has.
Actually, the paleomagnetic data from the next century shows that the auroral area moved away Japan and settled above Greenland. First author claims that historical accounts are consistent with the paleomagnetic evidence.
Paleomagnetic data also shows an auroral dip in the United Kingdom over the 18th century. This matches up with written accounts.
The researchers wanted to determine if aurora witness accounts match up with the paleomagnetic data. They wanted to find out if scientific data supports the notion that auroras can be seen in Japan at the 12th Century. They were able confirm this, as well as many other things.
Kataoka stated in a press release that "We concluded the 12th century and 18th centuries were excellent times for Japan and the United Kingdom respectively to observe auroras over the last 3,000 year."
Universe Today originally published this article. You can read the original article.
