Aurora is what happened when dark mode became the default for technical products and every one of them needed a hero image it did not have. Photography was wrong, illustration was slow, and flat colour on near-black looked like an unfinished page. Blurred overlapping gradient fields solved all three at once.
The reference is the aurora borealis, and the important property is borrowed directly: the light has no source you can point to. Colour bleeds through colour with no edge, no gradient stop you can locate, and no object casting it. That absence is the whole effect, and it is why a hard-edged gradient reads as something else entirely.
It became the default look of AI and infrastructure branding in the early 2020s, to the point of parody. The better executions add grain, which stops the smooth fields from banding on real displays and gives the surface something to be.