In the 18th century, night time in the streets of Kyoto would have been a dark and shadowy affair, with light coming only from gas lamps, torches, fires and, on certain evenings, the moon.
The night of 17 September in 1770, however, was different. The sky above the Japanese city was lit brightly by a red and orange shimmering magnetic field. The colour was breathtaking, throwing the steep hills that surround the city into stark relief.
The phenomenon was an aurora – the type of magnetic show that regularly lights up the skies in the high northern and southern latitudes. For an aurora to be visible over warmer latitudes is rare, but not unknown.
How do we know Kyoto was lit up like a celestial Christmas tree 247 years ago? Because, thankfully, a member of a local family, the Higashi-Hakuras, picked up some parchment and rendered the sight as a beautiful inked double-page spread.
The painter eventually incorporated the work into a book titled Seikai (“Understanding Comets”), which has lately emerged from a private collection and passed into the hands of researchers at the National Institute of Japanese Literature (NIJL) and National Institute for Polar Research (NIPR) in Tokyo.
The detail of the painting and accompanying text was enough for researchers to confirm the date of the uncommon storm, and enter the artwork as evidence in the quest to track the frequency of similar events.
“The magnetic storm on 17 September 1770 was comparable with or slightly larger than the September 1859 magnetic storm that occurred under the influence of the Carrington solar flare,” says Ryuho Kataoka of the NIPR.
“The 1859 storm was the largest magnetic storm on record, in which technological effects were widely observed. It was lucky for us that the 1770 storm predated our reliance on electricity.”
The chances of such a storm happening today – and being captured by modern cameras (as well, perhaps, as enthusiastic artists – are slim.
“We are currently within a period of decreasing solar activity, which may spell the end for severe magnetic storms in the near future,” Kataoka says.
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