The sun's solar cycles were once around three years shorter than they are today, a new analysis of centuries-old Korean chronicles reveals. This previously unknown anomaly occurred during a mysterious solar epoch known as the"Maunder Minimum," more than 300 years ago.
But just as the sun fluctuates within individual cycles, historical sunspot records show that over longer periods, spanning decades or centuries, the overall output of solar cycles can also rise and fall. In the new study, published Oct. 3 in the journal AGU Advances, researchers analyzed historic auroral records from Korea and found that solar cycles during the Maunder Minimum were only eight years long on average — three years shorter than modern cycles.
The dates when these auroras occurred show that solar radiation from the sun followed an eight-year cycle. —Gigantic radiation storms have been pummeling Earth for at least 10,000 years and could strike again