It's from the TIE Fighter PC game.
http://starwars.wikia.com/wiki/Magnetic_pulse
It's a torpedo that disables a ship's weapons systems, but not the engines. A good opportunity for those advocating a " weapons disabled " mechanic in the game.
No ordinance whatsoever packaged with the new TIE/sf, though, nor even anything about warheads being housed in the turret.