The formation of super-rings

The author has calculated the collision of a small neutral cloud (surface density approximately 10/sup 19/ cm/sup -2/) with a constant density galactic disk. Through the collision, a large amount of energy is deposited in a small volume of the galaxy, resulting in a supersonic expansion of very hot (10/sup 6/-10/sup 7/K) gas into the Galaxy and out of the galactic disk. The expansion generates a large cavity (a super-ring) with physical characteristics (diameter, velocity of expansion, etc.) in agreement with the observations, and a large volume of hot low-density gas with properties similar to those of the observed coronal gas. (31 refs).