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.

A plasma can be described as a gas to which a specific amount of energy has been added to separate the gas component molecules into a collection of ions, electrons, charge-neutral gas molecules, and other species in varying degrees of excitation. Depending on the amount of energy added, the resulting plasma can be characterized as thermal or nonthermal.


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.

A "partially ionized plasma" such as the Earth′s ionosphere is one that also contains neutral atoms.

See also: Adiabatic Plasma, Cold Plasma Model, Confinement, Electron, Fully Ionized Plasma, Ion, Ion Acoustic Wave, Langmuir Probe, Lorentz Gas, Magnetic Pressure, Plasma Discharge, Plasma Frequency, Plasma Wave, Quasineutral Plasma, Radio Frequency Heating, Weakly Ionized Plasma, Zeta Machine.

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Subjects: Physics