Models of collisional reactions between the hot (several keV) protons and neutral atomic hydrogen corona observed at Uranus by Voyager 2 are compared with the observations in order to deduce constraints on the coronal density. An upper limit is found for nH(5RU) of several tens of H/cm3 on the sunward side of Uranus and several H/cm3 on the dark side. The possibility that the hot plasma population might arise from photoionization and electron impact ionization of coronal and interstellar medium hydrogen in the magnetotail, followed by pickup and energization while convecting toward Uranus, is examined and rejected. ¿ American Geophysical Union 1988