Spotting the Northern Lights anywhere in the United States (except for Alaska and the Upper Midwest) would probably be one of most notable experiences in an American space fan’s life. Now imagine if it was China or Japan a thousand years ago and you didn’t know what caused these light shows. Odds are, you’d freak out a little bit… and write about it.
That’s what a team of Japanese scientists are hoping. They are browsing through ancient documents to see what kinds of solar storms folks living back then saw and recorded. They think that some of these documented auroral events could be from “great magnetic storms” coming from strong solar events. If so, these texts could help us understand just how frequently these storms occur, seeing as they’d be far more harmful today given our reliance on electricity.
Auroral events come from blasts of particles from the Sun (especially electrons) interacting with the Earth’s atmosphere and magnetic field, exciting the oxygen and nitrogen and causing them to let out their characteristic glow. Certain solar events like coronal mass ejections (CMEs), large blasts originating from knots in the solar magnetic field, can cause particularly bad solar storms that could paralyze power grids, endanger astronauts, and deliver strong, days-long auroras.
The researchers found lots of examples of these observations. Take this one from Fujiwara-no-Sadaie (aka Teika), the famous Japanese poet who mentioned prolonged storms on February 21st and 23rd, 1204 in his Meigetsuki:
On 1204/02/21, it was sunny. … After sunset, red vapor appeared in the direction of north and north-east. The lower part of red vapor was shaped like a rising moon and colored white and bright. Its stripes extended faraway and was like smokes in fires. There were four or five of white parts and three or four of red vapors appeared. Is it neither cloud nor stands within clouds? Its light did not get darken and red light is mixed in the white light. It is nothing but a mystery. It is also very dreadful.
On 1204/02/23, it was sunny and quite windy. … In the time when to put a fire on the lamp, red vapor appeared in the north and north-east. It was like a distant mountain burning. It was very dreadful.
Chinese writings show descriptions of auroral events even earlier:
On 14 Feb. 937, at night, red and white vapors appeared alternately, like a cultivated and exploited bamboo forest, from 23:00 to 3:00, muddily from north to the middle in the sky, flickering unstably went around the 28 lunar mansions and disappeared at the dawn.