Selection of the emission frequency of a dye laser with a nonlinear mirror

Nonlinear Waves in Magnetized Accretion Disksa

“…Also, the viscous force is negligible in (3). For a broad range of conditions, the quasi-static approximation holds where a1 du/dt 1 is negligible compared with the other terms in (3). In this case the accretion flow is subsonic and there is hydrostatic balance in the r direction.…”