j4k3 , 5 months ago

You are seeing the exhaust plume while it is still dense enough to reflect enough light from the sun.

There are several massive thermal layers in the atmosphere that effectively make isolation barriers at various heights. That is why the exhaust on the left appears unique in structure within a certain boundary. The upper layers of the atmosphere get really hot before getting really cold again. Like commercial jets fly in the cold part, but it gets hot, then cold above that. The rocket plume on the right is in that upper cold region; the outer most puffy/sparse/low Earth orbit region. You can tell because of how enormous the exhaust plume is expanding when there is very little atmospheric pressure to contain it.

There is very little atmosphere way up there and certainly not enough to produce Rayleigh scattering. If there was enough to produce Rayleigh scattering the exhaust plume would be hard to see with very little contrast against the background, but without, it makes a much higher contrast view against the mostly empty void of LEO space.