: of, relating to, or having the characteristics of an Alfvén wave
Alfvénic velocity
In a magnetic nozzle the Alfvén speed plays a role similar to that of the sound speed in a conventional nozzle. The transition from sub-Alfvénic to super-Alfvénic flow delineates a boundary beyond which the flow downstream has no effect upstream—which ensures that the detachment exerts no drag on the rocket.—Franklin R. Chang Díaz, Scientific American, November 2000