Draft:Partially ionized plasma

A partially ionized plasma is a plasma containing charged particles (electrons and ions) and neutral particles (atoms and/or molecules with no net electric charge).[1][2] In order for a fluid to behave like plasma rather than gas, the degree of ionization must be high enough for the behavior of the fluid to be governed by electromagnetic forces between particles.

Electromagnetic fields only exert a force on particles with a net electric charge. In a partially ionized plasma, the charged particles experience a Lorentz force but neutral particles do not, which can cause the charged particles and neutral particles to have different flow velocities. Collisions between charged and neutral particles lead to a drag force between the charged and neutral particle populations.[citation needed]

When the degree of ionization is very small, the plasma is sometimes referred to as a weakly ionized plasma. When it contains charged particulates, a partially ionized plasma will also be a dusty plasma.[citation needed]

Properties

Plasmas have high electrical conductivity,[citation needed] while gases are strong insulators.[citation needed]

Partially ionized plasma exhibits behavior not present in gases or fully ionized plasmas.[citation needed]

Unlike the phase transitions between other states of matter, the phase transition between gas and plasma is gradual rather than discrete.[citation needed]

Examples

In plasma technology

Plasma technology that makes use of partially ionized plasma include plasma globes, neon lights, fluorescent lamps, plasma arc welding, plasma displays, plasma arc furnaces, plasma cutting, and Hall-effect thrusters.

In planetary atmospheres

Examples of naturally occurring phenomena in planetary atmospheres that involve partially ionized plasma include lightning, sprites, and St. Elmo's fire. Planetary ionospheres such as Earth's ionosphere consist largely of partially ionized plasma. Partially ionized plasma can exists in planetary magnetospheres and aurorae.[verification needed] If hot enough, a fire can include weakly ionized plasma.[verification needed][clarification needed][dubious – discuss]

In astrophysics

Partially ionized plasmas exist in molecular clouds, accretion disks, protoplanetary disks, the interstellar mediums of galaxies, stellar atmospheres, and comet tails.

The atmospheres of stars often contain partially ionized plasma. For example, the photosphere of the Sun has ionization fractions of order 10−4 [citation needed] while the solar chromosphere has ionization fractions of order 10−2. Prominences and filaments contain partially ionized plasma. Substellar objects

The interstellar medium includes several phases.[citation needed] The cold neutral medium is estimate to have ionization fractions between 10−4 to 10−3, while the warm neutral medium is estimated to have ionization fractions ranging from 10−2 to 10−3.[citation needed]

The ionization fraction of fluid in molecular clouds is of order 10−7,[citation needed] and magnetic fields are known to influence the evolution of molecular clouds and the star formation process.[citation needed]

In cosmology

During the epoch of recombination, material in the universe transitioned from being a nearly fully ionized plasma into a partially ionized plasma. During the Dark Ages, near 10−4. In the epoch of reionization, material in the intergalactic medium became almost fully ionized.

References

  1. ^ Krishan, Vinod (13 September 2017). Physics of Partially Ionized Plasmas. Cambridge University Press. p. 1.
  2. ^ Ballester, José Luis; Alexeev, Igor; Collados, Manuel; Downes, Turlough; Pfaff, Robert F.; Gilbert, Holly; Khodachenko, Maxim; Khomenko, Elena; Shaikhislamov, Ildar F.; Soler, Roberto; Vázquez-Semadeni, Enrique; Zaqarashvili, Teimuraz (13 March 2018). "Partially Ionized Plasmas in Astrophysics". Space Science Reviews. 214: 58. doi:10.1007/s11214-018-0485-6.

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