This is quite interesting:
from the link:
As everyone knows, it is a circular explanation: no-one really knows what the earth lights are. The lights are seen (and filmed) mostly in night-time but the local people have also told about grey disc or cigar shaped objects in the air which don't reflect light. There haven't been any observations of aliens and no abductions have occurred though there's been a couple of strange animal deaths that resemble "animal mutilations".
possible interpretation issues.
I have also read that there is no heat associated with Hessdalen lights, which illiminates one type of possible cattle death.