Plasma during reentry.

[McWgogs]

I have a question regarding the visibility of plasma during reentry.

I've seen in space shuttle launch videos, there is some faint plasma before and after MECO, as i understand the shuttle is around 100 km and that's still in the higher atmosphere.

My question is: on a speed versus altitude/air density graph, where does plasma appear?
Let's say the top border would be 8km/s at 100km altitude

Any formula to calculate plasma visibility?

 

[McWgogs]

Anyone?

 

[-Pv-]

I cannot provide you with a plot, but I have watched all the launches the last several years and those with live camera views from the external tank definitely show a strong plasma field around the shuttle near MECO. To me, it looks like it increases just after the stack rolls to heads up and increases more as the Shuttle RCS fire in preparation for the tank separation. It might be possible to find these videos on NASA as they have become a part of nearly every recent crew day activity video, and the video review for the whole flight.
-Pv-

 

[Urwumpe]

The plasma generation depends on the local aerodynamic heat flux. At points where the density of the air is higher, you have more plasma. at the higher layers of the atmosphere, where you have no airflow as such anymore, such points are just caused by the collision of the air molecules with the space craft.