I see how you see it.
I rather look at it as plural "things" caused by a phenomenon. The Norhern Light is a light display in the sky. Lights caused by the Northern Light.
"Emission of auroral light." "Light emissions". Enough singular feeling to me.
Mind you, polar Light (and even Northern Light) is accepted in English, but somehow there is also a plural stream in your language (maybe a very old one made up by people who didn't understand it yet: "Look! Lights!"). I find it interesting that it deviates from most other languages I am aware of.
Everything in English is like that. You don't go to the sea and say, "Look at the wave." Even though the waves are caused by the same effects, they are individual parts of a large process.
Nobody in English says Northern Light. It's unheard of. If we talk about the effect it in a singular manner, we would say the aurora. Or aurora borealis. No native English speaker would call that by a singular title.