edit: http://www.amazon.com/Seveneves-A-Novel-Neal-Stephenson/dp/0... gives a bit more detail and it is likely it will not become a ring. Probably a lot of highly energetic reentrant debris capable of generating a lot of atmospheric heat.
edit: @jaquesm - i'm allowing for creative license, and was making guess explaining what would happened based on my gut feel for the plot direction. you're probably correct on the physics.
https://www.amazon.com/Seveneves-Novel-Neal-Stephenson/dp/00...