Abstract: | We take the vertical distribution of the radial and azimuthal velocities into account in spherical coordinates, and find that the analytic relation c
s0/ν
K
Θ=(γ?1)/2γ]1/2 is valid for both geometrically thin and thick accretion flows, where c
s0 is the sound speed on the equatorial plane, ν
K is the Keplerian velocity, Θ is the half-opening angle of the flow, and γ is the adiabatic index. |