plasma

Introduction
The development of plasma physics
Plasma oscillations and parameters
Basic plasma physics
- Plasma formation
- Methods of describing plasma phenomena
- Determination of plasma variables
- Waves in plasmas
  - Low-frequency waves
  - Higher frequency waves
  - Containment
- Applications of plasmas
Natural plasmas
- Extraterrestrial forms
- Solar-terrestrial forms
  - Regions of the Sun
  - Interaction of the solar wind and the magnetosphere
  - The ionosphere and upper atmosphere
  - The lower atmosphere and surface of the Earth
  - Magnetic fields

References & Edit History Quick Facts & Related Topics

Images & Videos

How scientists use lasers to learn about the universe

Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy.

reaction rate as a function of plasma temperature

Understand how the polarization of the light from cosmic background radiation influenced the early development of the universe

At a Glance

plasma summary

Related Questions

How are electrons and ions balanced in an ordinary plasma?
How can a moving plasma generate electricity through the magnetohydrodynamic dynamo effect?
How can electrons and positive holes in semiconductors show plasma behavior?
How can radar measure the temperature, density, and motion of plasma near Earth?
How did Eugene Parker explain the solar wind?
How did Hannes Alfvén contribute to the study of plasma physics?
How do free electrons in metals form a type of plasma?
How do magnetic fields influence plasmas in interstellar and interplanetary space?
How do spectroscopic observations help scientists study plasmas beyond the solar system?
How does a gas become ionized into plasma?
How does an electric field heat plasma through ohmic heating?
How does an electric field perpendicular to a magnetic field cause plasma particles to drift?
How does cyclotron resonance accelerate charged particles?
How does the ionosphere reflect or absorb some radio waves?
How hot is the plasma inside a lightning stroke?
How is a plasma jet produced between concentric electrodes?
What are noctilucent clouds made of?
What causes the pinch effect in a cylindrical plasma?
What chemical and metallurgical uses can plasma jets have?
What force pulls electrons back during a plasma oscillation?
What fusion-power milestone did the Joint European Torus achieve in 1991?
What fusion-power milestone did the Tokamak Fusion Test Reactor achieve in 1994?
Where is most visible matter in the universe found in the plasma state?
Which natural events on Earth produce plasma?
Why can plasma behave collectively even when its particles rarely collide?
Why did Irving Langmuir compare plasma oscillations to the motion of a jellylike substance?
Why does Earth’s magnetosphere extend farther on the nightside than on the Sun-facing side?
Why does a charged particle follow a helical path around a magnetic field line?
Why does a toroidal, doughnut-shaped plasma reduce end losses in fusion devices?
Why does the lower ionosphere lose much of its plasma after sunset?
Why is a fully ionized hydrogen plasma made of electrons and protons?
Why must a plasma be much larger than its Debye length?
Why must satellite radio signals have frequencies above the ionosphere’s highest plasma frequency?

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External Websites

UCAR Center for Science Education - Plasma
IOPscience - Cold Plasma Cancer Therapy - Plasma as a fourth state of matter
National Center for Biotechnology Information - PubMed Central - Plasma Modeling and Prebiotic Chemistry: A Review of the State-of-the-Art and Perspectives
LiveScience - States of Matter: Plasma

Britannica Websites

Articles from Britannica Encyclopedias for elementary and high school students.

plasma and plasma physics - Student Encyclopedia (Ages 11 and up)

plasma

state of matter

Also known as: plasma state

Written by

Michael C. Kelley

Professor of Electrical Engineering, Cornell University, Ithaca, New York. Author of The Earth's Ionosphere: Plasma Physics and Electrodynamics.

Michael C. KelleyAll

Fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Oct. 14, 2026 •History

plasma, in physics, an electrically conducting medium in which there are roughly equal numbers of positively and negatively charged particles, produced when the atoms in a gas become ionized. It is sometimes referred to as the fourth state of matter, distinct from the solid, liquid, and gaseous states. The negative charge is usually carried by electrons, each of which has one unit of negative charge. The positive charge is typically carried by atoms or molecules...

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