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Briefly, it is the study of the statistical properties of a field of charged particles, called a plasma. Sometimes called "the fourth state of matter" (besides solid, liquid, and gas), plasma in this context refers to a gas that has been subjected to enough energy to dissociate atoms from their electrons ( ionization), producing a cloud of ions and electrons. Because these particles are ionized (charged), the gas behaves in a different fashion than neutral gas in, for instance, the presence of electromagnetic fields.

A common fluid treatment of plasmas comes from a combination of the Navier Stokes Equations of fluid dynamics and Maxwell's equations of electromagnetism. The resulting set of equations, with appropriate approximations, is called MagnetohydrodynamicsMagnetohydrodynamics (MHD or magnetofluiddynamics is the academic discipline which studies the dynamics of electrically- conducting fluids. It is the study of the motions of electrically conducting fluids and their interactions with magnetic fields. Examp (or MHD for short).

Plasma physics is important in astrophysicsSpiral Galaxy ESO 269-57 Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties ( luminosity, density, temperature, chemical composition) of astronomical objects such as stars, galaxies, and in that many astronomical objects including starFor alternate meanings see star (disambiguation Hubble Space Telescope of the Sagittarius Star Cloud in the Milky Way Galaxy. A star is any massive gaseous celestial body in outer space. Stars appear as shining points in the nighttime sky that twinkle becs, accretion disks, nebulaThis article refers to nebulas in space. For the band Nebula, go to Nebula (band). Triangulum Emission Nebula NGC 604 lies in a spiral arm of Galaxy M33, 2. 7 million light-years from Earth. This nebula is a region in which stars are forming. A nebula (La, and the interstellar mediumThe interstellar medium (or ISM is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate "circumstellar" environment) within a galaxy. The matter normally consists of about 99% gas particles and u consist of plasma. It is also important in hypersonic aerodynamicsFluid dynamics Aerodynamics is a branch of fluid dynamics concerned with the study of gas flows. The solution of an aerodynamic problem normally involves calculating for various properties of the flow, such as velocity, pressure, density, and temperature,, since at hypersonic speeds the interaction of the shock waveFor the vector animation platform, see Macromedia Shockwave. In fluid dynamics, a shock wave is a strong pressure wave. See Rankine-Hugoniot equation. In compressible fluids such as air, disturbances such as pressure changes caused by a solid object movin and the boundary layer creates enough heat to ionize the air surrounding a body. This happens, for example, upon re-entry of the Space Shuttle into Earth's atmosphere. Plasma physics is used in work studying nuclear fusion since most known fusion reactions take place in plasma.

Fields of active research include (but of course are not limited to):

• Plasma equilibria and stability
• Plasma diagnostics
• Plasma sources
• Plasma interactions with waves and beams
• Industrial plasmas
• Plasma theory
• Plasma devices
• Nuclear fusion
• Fusion power
  • Magnetic fusion energy (MFE) -- tokamak, stellarator, reversed field pinch, magnetic mirror
  • Inertial fusion energy (IFE) (also Inertial confinement fusion - ICF)
• Space plasmas, e.g. Earth's plasmasphere (an inner portion of the magnetosphere dense with plasma)
• Plasma cosmology