Hello, Imagine a spherical chamber and a concentric spherical plasma confined within. We eject electrons at a constant rate from the chamber walls into the plasma. As the electron cloud approaches to the plasma, since it does not have electric field inside, nothing happens to the plasma. When the cloud first penetrates the plasma, I have difficulty in deciding what the electric field will look like and how the ions and electrons in the plasma will move. Only, when I think of the electric field a moment after the penetration, it occurs to me that the ions should move inwards and electrons outwards. But then the electric fields should cancel out each other (or not?) and the plasma should stay there (or return to its original state?) Please enlighten me.