There is a similar phenomenon that occurs with clouds that form in the upper atmosphere. They're called noctilucent clouds. This is the same concept that causes the exhaust to glow when the rockets are launched. The sun is below the horizon but the clouds/exhaust is high enough where the suns rays will refract off the clouds and give it an iridescent look or at least make it appear bright in the sky.
Tycoon5000 t1_jb9rgr4 wrote
Reply to What are some good sources I can use when finding out why the rocket fuel and exhaust particles separate during launch in the upper atmosphere causing that bright "bulb" of light? by redditslayer95
There is a similar phenomenon that occurs with clouds that form in the upper atmosphere. They're called noctilucent clouds. This is the same concept that causes the exhaust to glow when the rockets are launched. The sun is below the horizon but the clouds/exhaust is high enough where the suns rays will refract off the clouds and give it an iridescent look or at least make it appear bright in the sky.