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 has tracked auroral activity over the past 3,000 years to gain a better understanding of how auroras move, how they might 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 three thousand years worth of auroral drift by using historical accounts from different cultures.
Their research has been published in the Journal of Space Weather and Space Climate. Ryuho Kataoka (associate professor at the National Institute of Polar Research) is the paper's first author.
Over the past 3000 years, reconstruction of the auroral zone.
Kataoka, the first author, stated in a press release that the accurate knowledge of the auroral area over the past 3,000 year via the worldwide old witness record for auroras helps us understand the extreme magnet storms.
This study was influenced by science and ancient writings. Paleomagnetism refers to the study of magnetic evidence found in rocks. The researchers used paleomagnetic modeling to map Earth's auroral zones over time. 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Kataoka stated that the auroral zone is subject to changes in time and historical documents are available from around the globe over the course of a thousand years.
The global shape of the auroral area in 1200 AD (blue), and 1800 AD (red). Contours refer to apex fields intensities of 49.173.474 and 6178 nT. These correspond to 70, 65 and 60 magnetic latitudes. Japan's longitude (135 E), is towards the bottom. Image credit: Kataoka 2021 and Nakano 2021.
The Kings Mirror, an Old Norse text that the researchers used as a historical document is one of them. It has 70 chapters and was written in dialogue between fathers and sons. Magnus Haakonsson is the son and Haakon IV Haakonsson is the father. This text was written to teach Magnus how to handle royal affairs and prepare him to reign. It focuses on matters of court, morality and trade. The Kings Mirror contains descriptions of auroral activities over Greenland between 1200 and 1300 AD.
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 around 1200 AD. This is consistent with what The Kings Mirror shows. 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.
Reconstructed auroral zones in 2010 AD (left), and 1200 AD. (right). Image credit: Kataoka 2021 and Nakano 2021.
Paleomagnetic data also shows an auroral dip in the United Kingdom over the 18th century. This matches up with written accounts.
Left: Auroral Isochasm by Fritz (1881). These documents date back to 1700-1872 AD.
Right: A reconstruction of the auroral zone between 1800 and 1870 AD (black). This is possible deformation due to a 170-year integration (red).
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 that the 12th century and 18th centuries were the best times for Japan and Britain to see auroras over the past 3,000 years.
