Is your afterburner object a sprite? If so, just do something like
-->Is mouse down, afterburner opacity<100-------set opacity to Self.Opacity+300*dt
-->Else, afterburner opacity >0-------set opacity to Self.Opacity-300*dt
That will make it fade in and out where 300 is the speed. If your object is a particle object, just set the firing rate to something when the mouse is down and 0 when it isn't. I wouldn't recommend creating and destroying your afterburner object every time you click, though.