Radiation-pressure viscous instability
= Radiation-pressure viscous instability
In a characteristic vertical model of a radiation-pressure-dominated <alpha disk> with constant <opacity>, $\mu\sim\alpha p/\Omega\sim c/\kappa$ and $p\sim\Sigma\Omega^2H$ imply $H\propto\Sigma^{-1}$ and $\bar\nu\Sigma\propto\Sigma^{-1}$. The resulting $d(\bar\nu\Sigma)/d\Sigma<0$ gives a <viscous instability of an accretion disk>, distinct from a <thermal instability of a radiation-pressure-dominated alpha disk>.