northern lights vs aurora borealis

northern lights and aurora borealis both are nouns.

Word	Noun	Adjective	Verb	Adverb
northern lights	Yes	No	No	No
aurora borealis	Yes	No	No	No

As nouns, northern lights and aurora borealis are synonyms defined as:

northern lights and aurora borealis: the aurora of the Northern Hemisphere

northern lights (noun)	aurora borealis (noun)
the aurora of the Northern Hemisphere	the aurora of the Northern Hemisphere