MPD is a Russian designed
ion drive; that has been used on satellites for station keeping purposes.
etiology: MagnetoPlasmaDynamic (MPD) thrusters (aka magnetohydrodynamic (MHD).
Unlike a conventional ion drive it uses a radial magnetic field to control the ions as well as a static accelerating potential. It has advantages that it can run on a wide range of propellants and is flight tested.