Figure 7: Estimate of along rays due to short wave propagation through an enveloped inertia wave. In (a), the shaded regions represent horizontal velocities exceeding time-independent critical level velocity. In (b), the black lines show for each ray, one as each ray propagates into the center of the envelope, and the other as each propagates out of the envelope. The line through the center of the oscillations shows the average during propagation. It begins at zero and decreases toward the center of the envelope, then returns to zero as is exits the envelope.