Thank You Tom for the detailed answer!
This photo is taken in Iceland, Jökulsarlon lagoon.
Now I think that You are right that these brown areas are caused by aurora itself. Then I should leave this photo as it is.
I took many photos from different places around this lagoon and those other...
I would like to make large prints and then these brown spots or areas shall be ugly.
Color management shall be solve this problem but I did not find a way how to select them not affecting other colors.
Thank You for asking questions, it is important to me and I shall give explanations with pleasure.
I was reducing noise luminance 50 unit and color 50 unit in photoshop raw converter.
Then I was correcting WB because it is too purple and after reducing tint in raw converter these brown spots...
I have problem with large brown spots over the image. I was photographing northern lights with canon 5D MKII, ISO800, 10s and later discovered nasty spots over the whole image.
I made several shots and all these pictures have the same problem.
I show there only part of the picture to get...
I am new here but have used photoshop last 8 years and I have attended in photoshop courses. I am nature photographer and I am using photoshop for my artwork.
I am not a professional photoshop user and I have still much to learn. I hope to do it on your site :).
With Best Wishes