Suppose a satellite in LEO wich have a ion thruster, this ion thruster have a grid accelerator and in LEO there are a high density of plasma by the ionosphere, thus the particles of the ionosphere can enter the chamber of the thruster? if this occurs i think it can be a problem
For example, if the outer grid is biased negatively then will attract ions of the ionosphere and then produce a thrust in the opposite direction of the thrust generated by the thruster
And after the external ions enter the thruster, are they accelerated outward again?