Source of the photo
http://mno.hu/tudomany/kiserteties_felhok_europa_folott__kepek-191998
Author of the description
GK
Noctilucent clouds are bright in the night and they may create special forms, like the one on the photo. The phenomenon comes up when the sun under the horison enlights special (icy) clouds on the sky.
Source of description
http://mno.hu/tudomany/kiserteties_felhok_europa_folott__kepek-191998