What is mach diamond?

Mach Diamond is a phenomenon that occurs in supersonic flow when the shock waves generated by the object are reflected off the ground, forming a series of diamond-shaped patterns in the exhaust plume of the engine. It is named after Ernst Mach, an Austrian physicist who first described this phenomenon. The Mach diamond is formed due to a combination of shock waves and expansion waves in the exhaust plume of the engine. This phenomenon is commonly observed in military fighter jets, as their engines operate at high supersonic speeds. The formation of Mach Diamond indicates the efficiency of the engine operating in supersonic conditions.