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Plasma (ionized matter and related concepts)

Plasma is an ionized state of matter whose behavior is dominated by collective electromagnetic effects; it occurs in stars, lightning, neon lights and many technologies, and is central to fusion and space physics.

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Plasma is a state of matter in which a gas contains a significant fraction of free charged particles—electrons and ions—so that collective electromagnetic forces strongly affect its behavior. On length scales larger than the Debye length and time scales longer than the inverse plasma frequency, plasmas exhibit organized responses such as waves, currents and self-organization that distinguish them from neutral gases.

Key characteristics

Important concepts for describing plasmas include quasi-neutrality (approximate large-scale charge balance), Debye shielding (local screening of electric fields), and plasma oscillations (collective motion of charges). Plasmas may be thermal (particles share a temperature) or nonthermal (electron and ion populations differ). They also range from partially ionized, low-temperature processing plasmas to fully ionized, high-temperature plasmas in stellar cores.

Classification and phenomena

Plasmas are classified by degree of ionization, temperature, collisionality and magnetization. Magnetized plasmas interact strongly with imposed magnetic fields and can support phenomena such as magnetic reconnection, cyclotron motion and magnetohydrodynamic waves. Other common processes include turbulence, instabilities and particle acceleration.

Occurrence

  • Astrophysical: stars, stellar atmospheres, the interstellar medium and accretion disks.
  • Space and near-Earth: the solar wind, planetary magnetospheres and auroras.
  • Terrestrial and laboratory: lightning, fluorescent and neon lamps, plasma displays, and laboratory fusion devices.

Applications and technology

Low-temperature plasmas are widely used in semiconductor fabrication, thin-film deposition, surface treatment and sterilization. High-temperature plasmas are central to research into controlled nuclear fusion (for example in tokamaks and stellarators) and to space-propulsion concepts such as ion and Hall-effect thrusters. Plasma diagnostics—spectroscopy, probes and microwave methods—are essential for understanding and controlling these systems.

The term "plasma" in the physics sense was popularized in the early 20th century. Separate but related high-energy states, such as the quark–gluon plasma produced in particle colliders, share the name because they also involve deconfined constituents. Plasma science spans laboratory, industrial, space and astrophysical domains and remains an active field because of its complexity and technological importance.

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AlegsaOnline.com Plasma (ionized matter and related concepts)

URL: https://en.alegsaonline.com/art/77309

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