shock diamonds[′shäk ‚dī·mənz]
The shock waves that appear in the exhaust stream of a rocket; they are made visible by their luminosity and describe an approximate diamond configuration in side view.
A commonly observed diamond-shaped reflection, brilliantly luminous from an afterburner of jet engines, the exhaust of rockets, and space shuttles. These shock diamonds are disc-shaped shock waves, called Mach discs, which are formed as shock waves and re-reflect in the exhaust. Because the shock discs raise the temperature of gases moving through them, excess fuel is ignited, causing the glow recognized as shock diamonds.