First time I'v seen a good picture of a pulse jet engine. Wonder if they are synchronized?
actually, the J58 was a classic axial flow turbojet, but the inlet temperature to the turbine was limited at reaching about Mach 3, so at that speed, the majority of the thrust was from the afterburners. But you are correct, the exhaust plumes are being modulated by shock waves.SR-71 J58 motors are ram jets; what you see are the afterburner plumes.
actually, the J58 was a classic axial flow turbojet, but the inlet temperature to the turbine was limited at reaching about Mach 3, so at that speed, the majority of the thrust was from the afterburners. But you are correct, the exhaust plumes are being modulated by shock waves.