Plume from jet engines should expand in lower atmosphere like rocket engines

[Jason_25]

I noticed on my spaceplane that the jet thrust does not expand like the nuclear rocket thrust does.  I think that actually the jet thrust should expand more than the nuclear rocket thrust since both particle streams are "jets" and the exhaust velocity of the jet engine particle stream should be lower thus less coherent and expanding outwards more.

[lemon1324]

I'm not sure this is true, actually. Rockets pump in their own fuel and oxidizer, so the absolute exhaust pressure is constant regardless of altitude. Jets operate at a constant compression ratio, so as the atmosphere gets thinner the absolute pressure should go down, while the pressure ratio is the same at all altitudes. I'm pretty sure air breathing jets should have similar visual expansion as a result.

[Jason_25]

I am not quite sure what you are getting at.  But by the last sentence it looks like you are agreeing with me that the exhaust stream should expand.  It seems that the difference between jet turbines and rockets are not meaningful here as I have mentioned both are "jets".  Same as the jet from a gamma ray burst except with different particles and speeds.

[Jason_25]

I should clarify that when I say "lower atmosphere" I mean lower pressure.  In otherwords at high altitude.  I do not mean low altitude.