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Additional recommended knowledge
In plasma physics, the Debye length, named after the Dutch physical chemist Peter Debye, is the scale over which mobile charge carriers (e.g. electrons) screen out electric fields in plasmas and other conductors. In other words, the Debye length is the distance over which significant charge separation can occur. A Debye sphere is a volume whose radius is the Debye length, in which there is a sphere of influence, and outside of which charges are screened.
In space plasmas where the electron density is relatively low, the Debye length may reach macroscopic values, such as in the magnetosphere, solar wind, interstellar medium and intergalactic medium (see table):
Hannes Alfven pointed out that: "In a low density plasma, localized space charge regions may build up large potential drops over distances of the order of some tens of the Debye lengths. Such regions have been called electric double layers. An electric double layer is the simplest space charge distribution that gives a potential drop in the layer and a vanishing electric field on each side of the layer. In the laboratory, double layers have been studied for half a century, but their importance in cosmic plasmas has not been generally recognized.".
Debye length in a plasma
In a plasma, the Debye length is
The ion term is often dropped, giving
although this is only valid when the ions are much colder than the electrons.
Debye length in an electrolyte
or when the solute is mono-monovalent and symmetrical,
For water at room temperature, λB ≈ 0.7 nm.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Debye_length". A list of authors is available in Wikipedia.|