This image is edited to a slight degree. Cut, framed, and and I touched up the sky a bit, because I was too late to capture the perfect moment and it was already growing darker again
Sensor noise on higher gains I'd guess. Normally I take images like this in manual and fiddle around with the settings until I get it right. In this case I had to be quick because the light was changing by the minute so I shot in auto. But I agree with you, I also liked the effect here that's why I kept it.