Plasma is recognized as the fourth state of matter, distinct from solids, liquids, and gases. It is an ionized gas, meaning that sufficient energy is provided to free electrons from atoms or molecules, allowing both species, ions and electrons, to coexist. This state of matter is highly electrically conductive, dominated by long-range electric and magnetic fields. Plasma is characterized by several unique properties:
Interactions: Long-range collective motion of particles is common, leading to various waves and other collective phenomena.
Electrical Conductivity: Plasma has very high electrical conductivity, often treated as infinite for practical purposes.
Independently Acting Species: Plasma consists of two or more species (electrons and ions) with different charges and vastly different masses, leading to different behaviors and specific plasma waves and instabilities.
Examples of plasma in nature include lightning strikes, the aurora, and the sun. Technological applications of plasma include etching silicon chips for smartphones, advanced space propulsion systems, and controlled nuclear fusion reactors.