Plasma Astrophysics Applications by David Stern from NASA for an EM Universe


An electron at rest relative to you seems to create an electric force. If you start moving, the electron is observed to be moving relatively to you, and a moving charge acts like an electric current, creating a magnetic field. What you observe depends on your motion! Electric and magnetic fields are the same thing from different reference frames. Electric fields in space are associated with any streaming of plasma through a magnetic field. Electric fields drive through and bend magnetic fields. The magnetic field of the galaxy is just outside the heliosphere, and is pushed away from the sun and earth by the solar wind.

Particles in space carry an electric charge, and a moving electric charge can be viewed as equivalent to an electric current. Magnetic forces try to make plasma “co-rotate” with the Earth. Their effect is the same, as if magnetic field lines which thread the plasma are viewed as attached to it. Plasma conducts electricity, and earth’s atmosphere is an insulator.

Electric currents often flow in space without any voltage driving them. No electric field is involved, because the magnetic field is doing it all, when it has the appropriate structure. The electric field moves both protons and electrons in the same direction with the same velocity of both motions. The result is always sideways flow of the plasma, a bulk flow motion of the gas. When some powerful cause “pushes” plasma to move in some direction, an electric field helps achieve this. The positive and negative charges creating such a field need only a relatively small number of electrons to be moved to new positions. The motion of plasma — is changing the magnetic field line structure — that is associated with an electric field, such as the solar wind. Where can such electric fields come from ? FROM FAR OUT IN OUTER SPACE !

In 1861 Maxwell proposed the “Displacement Current” that fills all of space, so that an electric current can travel through empty space, but only for very fast oscillations — Light !

Electric phenomena tend to spread out in outer space, where every point can have its own voltage. The 3-dimensional voltage distribution is the electric field.