Distinction between progressive and standing waves. The top left panel is a zoom of Fig. 2d (same colorbar). Three horizontal dotted lines represent the frequencies chosen in Panels A)−C). In these panels, we show the radial velocity in the same region filtered at three different frequencies. Low-frequency waves are rapidly damped and cannot form g-modes (Panel A)). In contrast, for ω = 0.1 mHz and ω = 0.2 mHz (Panels B) and C)), we see modes oscillating between the two turning points (white lines).