Essential Guide to the EU – Chapter 6
Currents, Filaments and Pinches
Planetary nebulas often exhibit characteristic bi-polar symmetries with a centered plasma pinch, polar jets, and an equatorial torus. Image courtesy NASA, ESA and the Hubble Heritage Team
6.1 Thermal Motion and Current
It is important to distinguish between random thermal motion and uniform linear motion in a plasma. The latter is an electric current which flows due to the presence of an electric field.
The random thermal motion is measured by the temperature of the plasma, or by the temperatures of the ions and electrons separately if their temperatures are different. This motion, being a motion of charged particles, is also a form of current, but one which oscillates about an average position, as opposed to moving in one direction only. Strictly speaking, temperature can only be an accurate measure of the energy if the distribution of velocities of individual particles is Maxwellian, that is, if the distribution is equivalent to that which would result from elastic collisions between the particles.
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