  The accompanying fluid dynamics videos visualize the temporal evolution of
shock structures and sound waves in and around an under-expanded jet that is
impinging on a rigid surface at varying pressure ratios. The recordings were
obtained at frame rates of 500 kHz to 1 Mhz using a novel pulsed illumination
source based on a high power light emitting diode (LED) which is operated in
pulsed current mode synchronized to the camera frame rate.
