Plasma

The fourth state of matter (along with the other states of matter: solids, liquids and gases) in which one or more electrons have been stripped from the atoms forming an ion gas. Therefore, capable of conducting electric currents. It is estimated that more than 99% of matter in the universe exists as plasma; examples include stars, nebulae, and interstellar particles. The temperature of a typical plasma may be 100,000 K or more and vary in particle density from about 10⁶m^-3 (solar wind) to 10³⁰m^-3 (core of star). Plasmas are relatively rare natural occurrences on earth, but many applications of plasma discharges have been found. Examples of plasma can be found in lightning, the Aurora borealis, fluorescent and neon-type lights, arc welding, and machines built to study nuclear fusion. A "partially ionized plasma" such as the Earth's ionosphere is one that also contains neutral atoms.

See also: Electron, Ion, Langmuir Probe, Zeta Machine.