Heya, I've taken a look at ancient/medieval accounts of the aurora here:

• [Were there ever religious pilgrimages to the northern lights?] (https://redd.it/3wsjqk)

One thing that I didn't really hit on explicitly is the reminds that Europe, latitude-wise, is a lot farther north than at least Americans tend to think. It seems sighting the aurorae was pretty common among Romans and early medieval people, or at least, frequent enough not to cause massive alarm.