As this B-1B Lancer climbs higher into the sky, hot exhaust gases leave the four individual engines. These four exhaust plumes rapidly combine with one another to create one large exhaust wake. This wake is visible to the human eye because the high temperature exhaust changes the density of the air relative to the surrounding atmospheric air, which changes the refractive index. When light travels through the exhaust, it gets distorted enough for the turbulent air to be seen by the naked eye as it is in the image above.
This picture is an interesting depiction of science and art because it takes a great deal of engineering to lift a plane off the ground and the sight of it is quite beautiful if you look at the fluid flow of the exhaust.
Image credit: Tyler Rogoway https://www.flickr.com/photos/vector1771/8205422666/