Individual electrons can easily, and without any realistic prospect of detection, "enter" any sovereign's territory.

And vice-versa too: electrons can only enter if and as others leave.

The point where those electrons enter an electrical circuit is called the "source" of electrons.

Because many more electrons enter the cold plasma than exit it, part of the cold region becomes negatively charged.

An electron enters this box and an electromagnetic pulse exits through a small exit slit.

The cycle then repeats as those electrons enter the cathode material again.

Each cylinder lines up parallel to the optical axis into which electrons enter.

Ions and electrons enter the Jovian magnetosphere by all of the means outlined in section 9.1.1.

However, during this interaction an electron may also either enter or leave an atom.

The additional electron will be entering an orbital farther away from the nucleus.