Help Me Out... Is This Some Weather Phenomenon?

[Bailey Guns]

KC-46 flew over today and I noticed it had this weird halo around it. Didn't have the camera with me. 20 mins later another (or the same one) came over again. Same weird halo but this time I got a picture. A C-17 had come over as well but I didn't notice this halo effect. The C-17 was lower, though. The KC-46 was just skirting in and out of the lower edge of the overcast. Is there some physical explanation for this? Static electricity or something? Reflections from the clouds? I don't think I've ever noticed this before.

ETA: The C-17 was also not directly overhead, either. It was maybe 1/4 mile off to the right in relation to the right wing of the KC-46. Maybe it was just because it was directly overhead.