The problem with the density of smoke in the simulation

[Cheburash]

Hello!
I have a scene with fire and smoke simulation.

I have changed the parameters of gravity to make fire and smoke tending down to the ground (it will be a fiery trail of soaring object).
Below there is a plane-obstacle for the fire and smoke, so the smoke should be spread over the surface.
However, for some reason, somewhere in the middle of the simulation, instead of a thick cloud of smoke, I see a very small amount of smoke along the surface, which spreads not evenly over it.

What could be the reason, and how can I fix it?
Blend file: http://blend-exchange.giantcowfilms.com/b/1142/
Screenshots with the settings are below.

P.S. The lighting in the scene is not very good, that’s why the smoke looks black, and the topology of the fire emitter is not the best, but I think this is not the reason…

P.S.P.S. I tried to increase the dissolve time, but after the first big bunch of smoke, smoke density decreases again. Also, I do not understand why the smoke spreads over the surface so uneven:

[Martin_Norris]

Hi,

I am not entirely sure of what you are trying to achieve, but I guess you want something like billowing clouds of smoke as if this was a rocket launch.

If so then I think that you are going to have to fake it in a different way because the smoke simulator does not have the self-collision interaction you would need to make the smoke billow.
That is the new smoke generated does not vigorously displace the existing smoke
Think of a rocket exhaust as expanding clouds of gases where the newly created gas displaces the existing gases
From what I can tell of the simulator the smoke does not interact like this, and instead follows arbitrary paths.

Possibly you could fake the effect using some force fields to push the smoke away from the ground and otherwise shape it
Or alternatively have an animated cloud at the base to represent the billowing effect.

Good luck