The video was created by Alex Rivest using footage from the International Space Station.
The visible yellow and green/blue capped line represents atmosphere reaching ~100km above the surface of the earth. The colours are not reflected light, and not pollution, but rather are light generated from the components in the atmosphere itself. Yes, the atmosphere gives off its own light, in a chemiluminescent process called “airglow” or “night glow.”
It’s hard to accept that only this thin layer separates us from sure death. At least for me it is. [Aurora Night Glow — Thanks Alex!]