Radial buoyancy frequency
= Radial buoyancy frequency
{title2=$N_r^2$}
The radial buoyancy frequency describes restoration of a radially displaced parcel in a stratified <astrophysical disk>. With a dimensionless <specific entropy> $S$, its square is proportional to $-\rho^{-1}(dP/dr)(dS/dr)$. Negative $N_r^2$ means an adverse entropy stratification, but <epicyclic motion> can still stabilize the parcel. For smooth <thin disk> profiles, $|N_r^2|$ is usually of order $(H/r)^2\Omega^2$.