A correction about the light phenomenon of Oct 2nd 2015

I've made a possible mistake in my comments about the light phenomenon that occurred at the Atlas V rocket launch on October 2015. I said that the phenomenon was not caused by the exhaust of the rocket, but as you can see in the photo above, the plume from the exhaust of an Atlas V rocket does widen a lot when nearing high altitudes. The photo is one from a different launch, yet from the same type of rocket. Its shape is almost similar to the shape of the bright giant plume witnessed in October 2015. This makes it more likely that the unexpected light phenomenon was caused by the exhaust of the rocket. Yet it does not explain how the plume grew so large and how it turned into a bright blue color.