When an object penetrates the #atmosphere at the crazy speeds of orbital mechanics, the air is compressed into a shockwave in front of the object and heats up to very high temperature 🌡️.

After colliding with our object, the air in the zone of the shockwave can achieve local temperature of several thousand to several tens of thousands of degrees. This has the effect of ripping electrons from atoms, #ionizing the matter, and causing it to enter into a #plasma phase https://spaceandscience.fr/en/blog/atmospheric-entry

@spaceflight actually, the point depends on the solar activity. A more energized atmosphere would result in a higher altitude, at which gravity gets overpowered by aerodynamics forces.

The Karman line is only for reference here, I suspect they use a calculated dynamic pressure for telling the autopilot when to begin adaptive control.