What are the climatological effects to the surface of a planet where the atmosphere gives way to vaccum? (diagram included)

(Please see diagrams) This is a question regarding an area of a Rocheworld scenario that I haven't found anything on.

It is suggested that the OUT side of a planet that is tidally locked with another is actually exposed to the vacuum of space because the gravity has pulled the atmosphere away from that area and towards the IN side which is facing the other planet with which its locked. But that must create a narrow area (a band around the planet?) which is neither fully covered in atmosphere nor fully exposed to vacuum.

On Earth the atmosphere thins out the higher we go. But on either of the Rocheworld planets the atmosphere would thin out right on the land the further you moved away from the twin planet. Potentially one could "walk" through a thinning atmosphere and right into the vacuum of space. That side of the planet, I imagine, would be like the surface of the moon (but with that planets gravity[?]).

But what would we experience in that band between the full atmosphere area and the vacuum exposed area?

See the diagram I drew below. (Hopefully all the other science is correct enough to understand the question.)

Edit: Its been suggested that a Rocheworld is impossible. Its also been suggested that it is possible. Lets hand wave that for the sake of the question. Thanks.

SECOND EDIT with diagram: Some of the responses suggest that my notions of the atmospheric conditions are off. I was wondering if you think this is more "correct"? If so, it removes the idea that the OUT side of the planets would be exposed to the vacuum of space. Hopefully this 2nd diagram is self explanatory.

Although this does raise another concern... What is the shape of the shared atmosphere area, and does it leak out so badly that nothing could really cross between the two planets? Again, Thanks.

3rd edit: @neophlegm gives a great answer below that this third diagram illuminates. He has a great diagram of his own as well.

whew

posted about 6 years ago

Len‭

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