An ancient solar storm left clues in tree rings and a famous poet's diary: 'Red lights in the northern sky'

The silhouette of what looks like mountains on the bottom of the screen with bright pink and red lights in the sky above. .

The solar cycle was several years shorter and the sun was experiencing an unusually active phase at the beginning of the 13th century — at least, that's the story told by evidence left behind in tree rings and historical records that suggest a burst of protons and enhanced coronal mass ejections battered Earth between the years 1200 and 1204 CE.

More specifically, scientists led by Hiroko Miyahara of the Okinawa Institute of Science and Technology (OIST) Solar–Terrestrial Environment and Climate Unit in Japan have found remnants of a dramatic solar proton event in tree rings dating back 825 years.